Wireways and Auxiliary Gutters
Remake batch 26: rewritten from scratch under the authoring cheatsheet with datasheet constraints; neighbors re-pointed to the new scope boundaries; the electrical code is now the adopted-electrical-code project fact
Showing changes from Rev 3
to Rev 4
in Wireways and Auxiliary Gutters.
---
title: Wireways and Auxiliary Gutters
category: Electrical
−toc_depth: 3
description: >
− When to use: Selection, sizing, and installation of sheet-metal and nonmetallic
− enclosed raceway troughs (wireways per NEC Articles 376 and 378) and supplemental
− conductor enclosures adjoining switchgear, switchboards, panelboards, meter centers,
− and distribution centers (auxiliary gutters per NEC Article 366). Covers lay-in and
− pull-through configurations, hinged- and lift-off-cover styles, NEMA 1/3R/4/4X/12
− enclosure types, fittings (elbows, tees, crosses, reducers, end caps, splice plates),
− support hardware, and conductor fill and derating calculations for commercial,
− industrial, institutional, and heavy-industrial work.
− Not intended for: conduit raceways (use [[sync/raceways-and-conduit]]); cable tray
− (use [[sync/cable-tray]]); busway and plug-in bus duct (use [[sync/busway]]; metal-enclosed bus above 600 V, [[sync/medium-voltage-bus-duct]]); the
− conductors and cables pulled through the trough (use [[sync/conductors-and-cables]]);
− grounding and bonding conductors within the enclosure (use [[sync/grounding-and-bonding]]);
− panelboard, switchboard, and switchgear enclosure interiors (use
− [[sync/panelboards]], [[sync/low-voltage-switchboards]],
− [[sync/low-voltage-switchgear]]); and wiring troughs integral to an MCC lineup
− (use [[sync/motor-control-centers]]).
+ When to use: Metal wireways under NFPA 70 Article 376, nonmetallic wireways under Article 378, and auxiliary gutters under Article 366, listed to UL 870, used to carry, group, and give access to insulated conductors rated 1000 V and below between and alongside switchgear, switchboards, panelboards, meter centers, motor control centers, control panels, and the raceways that serve them. Covers the trough as a listed product: the trough type and the classification of each run as a wireway or an auxiliary gutter, the voltage rating, the material, enclosure type, and finish, the covers and knockouts, the cross-section and conductor fill, the 30-conductor ampacity adjustment threshold, the splice and tap space, the fittings, end plates, equipment connectors, and expansion fittings, the bonding continuity of the assembly, the supports and their spacing, the 30 ft auxiliary gutter length limit, the connection to the equipment the trough adjoins, field testing, installation, warranty, and spares, for indoor and outdoor locations.
+
+ Not intended for: conduit, tubing, boxes, conduit bodies, and surface raceways ([[sync/raceways-and-conduit]]); open-top cable tray ([[sync/cable-tray]]); busway rated 600 V and below ([[sync/busway]]) and bus above 600 V built to IEEE C37.23 ([[sync/medium-voltage-bus-duct]]); the wiring gutters and wireways inside a panelboard, switchboard, switchgear, or motor control center, which that equipment's listing furnishes ([[sync/panelboards]], [[sync/low-voltage-switchboards]], [[sync/low-voltage-switchgear]], [[sync/motor-control-centers]]); the conductors pulled through the trough, their ampacity, and their splice and tap connectors ([[sync/conductors-and-cables]]); the equipment grounding conductors, their sizing, and the bonding means of the system the trough is part of ([[sync/grounding-and-bonding]]); the nameplates and warning signs on an enclosure face ([[sync/equipment-labeling]]); raceway markers, conductor tags, and color coding ([[sync/electrical-identification]]); the firestop system installed where a trough passes through a rated assembly ([[sync/firestopping]]); the design of seismic restraint for the supports ([[sync/vibration-isolation-and-seismic-restraint]]); wireways in hazardous classified locations ([[sync/electrical-hazardous-locations]]); and the testing organization, its instruments, and the compiled test report ([[sync/electrical-acceptance-testing]]).
---
# Scope {toc}
−## This standard covers enclosed metal and nonmetallic troughs used to group, route, and access insulated conductors at and between electrical equipment, comprising both wireways (a raceway) and auxiliary gutters (a supplemental enclosure). {note}
+## This standard governs the wireway and the auxiliary gutter as a listed product: the trough and its cover, the fittings that turn, branch, reduce, close, and connect it, the hardware that holds the sections together and keeps the assembly electrically continuous, the supports that carry it, and the field work that classifies, fills, bonds, and tests it. {note}
−## The defining distinction in this standard is between a wireway and an auxiliary gutter, because each is governed by a different NEC article with different fill limits and application restrictions. A wireway is a sheet-metal or nonmetallic trough with a hinged or removable cover used as a raceway to carry conductors from point to point; it is governed by NEC Article 376 (metal) or Article 378 (nonmetallic) and has no length restriction. An auxiliary gutter is a supplemental enclosure that extends from and supplements the wiring space of equipment such as switchboards and distribution centers; it is governed by NEC Article 366 and is not a raceway. {note}
+## A wireway is a sheet metal or nonmetallic trough with a hinged or removable cover, in which conductors are laid in place after the trough is installed and reached again at any point along its length, and it is a raceway under NFPA 70 Article 376 or Article 378 with no limit on its length. An auxiliary gutter is the same trough used for a different purpose: it extends the wiring space of switchgear, a switchboard, a panelboard, a meter center, or a motor control center so that conductors can be spliced, tapped, and distributed to the equipment it serves, and it is a supplemental enclosure under NFPA 70 Article 366 rather than a raceway, limited to 30 ft beyond the equipment it supplements. {note}
−## The two assemblies frequently use identical hardware and finishes, so the governing article must be established per segment rather than per product; a single physical trough can change classification along its length. {note}
+## Which article governs a run is settled by what the run does, not by what it is made of; a trough that carries conductors between two pieces of equipment is a wireway, and the same catalog trough bolted to the top of a switchboard to splice and distribute its feeders is an auxiliary gutter. The two articles set different support intervals, different length limits, and a different rule for when the ampacity adjustment factors apply, so every run is classified before it is filled. {note}
−## Each trough segment shall be classified on the drawings or in the conductor fill schedule as either a wireway (Article 376 or 378) or an auxiliary gutter (Article 366).
+## The following are governed elsewhere and are outside this standard: {note}
−## Conductor fill, support spacing, ampacity derating, and length limits shall be calculated using the NEC article that governs the segment's classification.
+- conduit, tubing, boxes, conduit bodies, and surface raceways, under [[sync/raceways-and-conduit]]
+- open-top cable tray, under [[sync/cable-tray]]
+- busway rated 600 V and below, under [[sync/busway]], and bus above 600 V built to IEEE C37.23, under [[sync/medium-voltage-bus-duct]]
+- the wiring gutters and the horizontal and vertical wireways inside a panelboard, a switchboard, switchgear, or a motor control center, under [[sync/panelboards]], [[sync/low-voltage-switchboards]], [[sync/low-voltage-switchgear]], and [[sync/motor-control-centers]]
+- the conductors pulled through the trough, their ampacity and adjustment factors, and the connectors used at splices and taps, under [[sync/conductors-and-cables]]
+- the equipment grounding conductors, their sizing, and the bonding means of the system, under [[sync/grounding-and-bonding]]
+- the nameplates, directories, and warning signs on an enclosure face, under [[sync/equipment-labeling]]
+- raceway markers, conductor tags, and conductor color coding, under [[sync/electrical-identification]]
+- the through-penetration firestop system installed around a trough at a rated wall or floor, under [[sync/firestopping]]
+- the design of the seismic restraint of the supports, under [[sync/vibration-isolation-and-seismic-restraint]]
+- the protection technique and wiring method inside a hazardous classified location, under [[sync/electrical-hazardous-locations]]
+- the testing organization, its instruments, and the compiled field test report, under [[sync/electrical-acceptance-testing]]
−## Wireways and auxiliary gutters shall be UL 870 listed assemblies unless a field-fabricated auxiliary gutter is expressly permitted and detailed in accordance with NEC 366.6.
+## Wireways, auxiliary gutters, and their fittings shall be listed and labeled to UL 870 by a Nationally Recognized Testing Laboratory, except where the datasheet under Quality Assurance permits an unlisted sheet metal auxiliary gutter.
−```datasheet
−label: Primary assembly classification
−type: radio
−options:
− - Wireway, metal (NEC Article 376 raceway)
− - Wireway, nonmetallic (NEC Article 378 raceway)
− - Auxiliary gutter (NEC Article 366 supplemental enclosure)
−drawing_ref: "wireway and gutter classification schedule"
−default: deferred
−```
+## Wireways and auxiliary gutters shall be installed in accordance with [[parameter: adopted-electrical-code]] and the manufacturer's installation instructions.
+## The routing, the extent, and the mounting elevation of each run shall be as indicated on [[drawing: the electrical plans and equipment elevations]].
+
# Referenced Standards {toc}
## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
−## Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+## Where the contract documents, the Authority Having Jurisdiction, or two referenced standards impose conflicting requirements, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
−## The edition of NFPA 70 (NEC) that applies shall be the edition adopted by the authority having jurisdiction for the project. {note}
−
| Standard | Title |
|----------|-------|
−| NFPA 70 (NEC) Article 100 | Definitions (Auxiliary Gutter; Wireway; Raceway) |
−| NFPA 70 (NEC) Article 366 | Auxiliary Gutters |
−| NFPA 70 (NEC) Article 376 | Metal Wireways |
−| NFPA 70 (NEC) Article 378 | Nonmetallic Wireways |
−| NFPA 70 (NEC) Table 310.15(C)(1) | Adjustment Factors for More Than Three Current-Carrying Conductors |
| UL 870 | Wireways, Auxiliary Gutters, and Associated Fittings |
+| UL 50 | Enclosures for Electrical Equipment, Non-Environmental Considerations |
+| UL 50E | Enclosures for Electrical Equipment, Environmental Considerations |
| NEMA 250 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
−| ANSI/NEMA 70 | National Electrical Code (as adopted) |
+| NFPA 70 | National Electrical Code (Articles 250, 300, 312, 366, 376, and 378) |
+| ASTM A653 | Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process |
+| ASTM A123 | Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products |
+| ASTM A240 | Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Applications |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapter 13) |
+| ANSI/NETA ATS | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
# Submittals {toc}
## Action Submittals {toc}
−### The Contractor shall submit the following action submittals for review prior to fabrication or ordering:
+### The Contractor shall submit the following for review before any trough is ordered:
−- Product data for each wireway and auxiliary gutter type, including cross-sectional dimensions, material, finish, NEMA enclosure type, voltage rating, and UL 870 listing.
−- Product data for all fittings, including elbows, tees, crosses, reducers, end caps, splice plates, couplings, and expansion fittings.
−- Conductor fill calculations for each trough segment, identifying segment classification (wireway or auxiliary gutter), interior cross-sectional area, conductor count and size, computed percent fill, and applied ampacity adjustment factor.
−- Shop drawings showing routing, dimensions, support locations and types, section joints, and coordination with adjacent equipment and other trades.
−- Support and seismic anchorage details where required by the project structural criteria.
+- shop drawings for each run giving the routing in plan and elevation, the classification of the run as a wireway or an auxiliary gutter, every straight section and fitting by catalog designation and length, the cover style, the location and type of every support, the location of every splice, tap, and power distribution block, and the connector at each piece of equipment the run adjoins
+- product data for the trough series giving the UL 870 listing, the enclosure type, the material and sheet thickness, the finish system, the interior cross-sectional area of each size furnished, the voltage rating, the knockout arrangement, and the support interval for which the series is listed
+- the conductor fill calculation for each run, giving the interior area, the conductors in the fullest cross-section with their sizes and insulation types, the percentage of fill, the count of current-carrying conductors at that cross-section, and the percentage of fill at every splice and tap point
+- the seismic restraint arrangement of the supports, where the datasheet requires restraint
```datasheet
−label: Action submittals required
+label: Action Submittals
type: checkbox
options:
− - Product data (troughs)
− - Product data (fittings)
− - Conductor fill calculations
− - Shop drawings (routing and supports)
− - Support and anchorage details
+ - "Shop drawings with run classification"
+ - "Product data with listing, enclosure type, and interior area"
+ - "Conductor fill calculation for each run"
+ - "Seismic restraint arrangement"
default:
− - Product data (troughs)
− - Product data (fittings)
− - Conductor fill calculations
− - Shop drawings (routing and supports)
+ - "Shop drawings with run classification"
+ - "Product data with listing, enclosure type, and interior area"
+ - "Conductor fill calculation for each run"
+constraint: all_of
```
+### The classification is written on the shop drawing because it is the one decision every later check depends on: the reviewer who finds a 40 ft auxiliary gutter or a nonmetallic wireway supported at 5 ft intervals finds it on the drawing, before the trough is ordered, rather than at the rough-in inspection. {note}
+
+### No trough shall be ordered until the action submittals covering it have been reviewed and returned.
+
## Informational Submittals {toc}
−### The Contractor shall submit the following informational submittals:
+### The Contractor shall submit the following with or before the action submittals:
−- Manufacturer installation instructions for the specified troughs and fittings.
−- UL 870 listing documentation, including the listed enclosure type and corrosion-protection classification.
−- Where field-fabricated auxiliary gutters are permitted, evidence that the sheet-metal and construction comply with NEC 366.6.
+- the manufacturer's installation instructions, including the support interval the series is listed for in each orientation, the cover fastening, and the bonding hardware at each joint
+- the listing documentation for each environmental type furnished, showing the trough and the fittings listed for that type
+- for a nonmetallic trough, the manufacturer's published coefficient of thermal expansion, the ambient temperature range the trough is listed for, and the sunlight-resistance marking where the trough is installed outdoors
+- for a trough installed in a corrosive atmosphere, the manufacturer's written statement that the material and finish furnished are suitable for the atmosphere named in the Environmental and Service Conditions
```datasheet
−label: Informational submittals required
+label: Informational Submittals
type: checkbox
options:
− - Manufacturer installation instructions
− - UL 870 listing documentation
− - Field-fabrication compliance evidence (if applicable)
+ - "Installation instructions with listed support intervals"
+ - "Listing documentation for the environmental type"
+ - "Nonmetallic trough expansion and temperature data"
+ - "Corrosive atmosphere suitability statement"
default:
− - Manufacturer installation instructions
− - UL 870 listing documentation
+ - "Installation instructions with listed support intervals"
+ - "Listing documentation for the environmental type"
+constraint: all_of
```
## Closeout Submittals {toc}
−### The Contractor shall submit the following closeout submittals:
+### The Contractor shall submit the following before any run is accepted:
−- Record drawings showing as-installed routing, segment classifications, and fitting locations.
−- Field test reports for equipment grounding conductor continuity across section joints.
+- record drawings reflecting the as-installed routing, the classification of each run, every fitting, support, expansion fitting, splice, tap, and power distribution block, and every penetration of a rated assembly
+- the field test report for each run, giving every measured value, the acceptance criterion applied, and the tester's determination
+- the warranty certificate identifying each run by designation and the warranty commencement date
+- a signed receipt from the Owner for the spare parts delivered
```datasheet
−label: Closeout submittals required
+label: Closeout Submittals
type: checkbox
options:
− - Record drawings (as-installed)
− - Grounding continuity test reports
+ - "Record drawings"
+ - "Field test reports"
+ - "Warranty certificate"
+ - "Spare parts receipt"
default:
− - Record drawings (as-installed)
− - Grounding continuity test reports
+ - "Record drawings"
+ - "Field test reports"
+ - "Warranty certificate"
+ - "Spare parts receipt"
+constraint: all_of
```
# Quality Assurance {toc}
−## Wireways, auxiliary gutters, and associated fittings shall be products of a single manufacturer to the greatest extent practicable so that fittings, covers, and finishes mate without field modification. {note}
+## Listing {toc}
−## All troughs and fittings shall be UL 870 listed and bear the listing mark, except field-fabricated auxiliary gutters permitted under NEC 366.6.
+### Every wireway, every fitting, and every nonmetallic auxiliary gutter shall be listed to UL 870 and shall bear the listing mark of the laboratory that listed it.
+### Whether an auxiliary gutter of sheet metal may be furnished unlisted shall be as indicated in the datasheet.
+
```datasheet
−label: Product listing requirement
+label: Sheet Metal Auxiliary Gutter Listing
type: radio
options:
− - UL 870 listed (factory assembly)
− - UL 870 listed troughs with field-fabricated gutter permitted (NEC 366.6)
−default: UL 870 listed (factory assembly)
+ - "Listed to UL 870"
+ - "Unlisted sheet metal gutter constructed as NFPA 70 Article 366 permits"
+default: "Listed to UL 870"
```
−## The installer shall be experienced in the installation of enclosed raceway and supplemental enclosure systems of the type and size specified.
+### NFPA 70 366.6 requires a sheet metal auxiliary gutter to be listed, and permits one that is not listed only where it is constructed to the sheet thickness, continuity, and cover requirements of NFPA 70 366.100; the listed gutter is the catalog trough every manufacturer ships, and the unlisted gutter is a custom sheet metal box a shop fabricates for a meter center or a switchboard whose wiring space no catalog size fits. The listed product is what nearly every project uses, and the unlisted gutter is accepted where the geometry leaves no listed alternative and the Authority Having Jurisdiction accepts the shop's construction. {note}
−## Conductor fill and ampacity derating calculations shall be prepared and stamped by, or under the direction of, the Engineer of Record where required by the AHJ.
+### Where an unlisted sheet metal auxiliary gutter is selected, the Contractor shall submit its fabrication drawings, sheet thickness, and cover fastening with the action submittals, and the gutter shall not be fabricated until the Authority Having Jurisdiction has accepted it.
−## UL 870 (9th Edition, 2016, reaffirmed as an ANSI standard in 2023 with no technical changes) is the single product safety standard covering both wireways and auxiliary gutters and their fittings. {note}
+## Source Limitations {toc}
+### The straight sections, covers, fittings, end plates, equipment connectors, expansion fittings, and joint hardware of a run shall be furnished by one manufacturer as one product series under one UL 870 listing.
+
+### Every run of the same trough type and enclosure type on the project shall be of one manufacturer's series, so that covers, fittings, and hardware interchange across runs.
+
+### A fitting from another series bolts to a trough whose flange pattern it was not made for, and the joint it makes is neither the listed joint nor the one the bonding continuity of the assembly was tested with; a project with two series on it also carries two sets of spare covers and two lengths of cover screw for the life of the installation. {note}
+
+## Installer Qualifications {toc}
+
+### Wireways and auxiliary gutters shall be installed by a licensed electrical contractor, with the conductors laid in and the splices and taps made by journeyman electricians under that contractor's supervision.
+
# Environmental and Service Conditions {toc}
−## Enclosure selection shall match the environment of each installed location, because the NEMA enclosure type controls protection against water, dust, and corrosion and a mismatch is a common field deficiency discovered after rough-in. {note}
+## Installed Locations {toc}
−## NEMA type definitions for wireway and auxiliary gutter selection: Type 1 is general-purpose indoor, suitable for clean dry electrical rooms only (not wet, damp, or outdoor); Type 3R is rain-tight for outdoor use; Type 4 is watertight; Type 4X is watertight with corrosion resistance for washdown and corrosive atmospheres; Type 12 is dust-tight and drip-tight for industrial interiors. {note}
+### A trough installed in a wet location, outdoors, or where it is exposed to rain, dripping, or splashing water shall be listed for wet locations and shall carry the enclosure type the Enclosure Type article requires for that location.
−## Wireways and auxiliary gutters installed in wet or damp locations shall be NEMA Type 3R minimum.
+### A trough shall not be installed where it is subject to severe physical damage, including a loading dock, a vehicle aisle, or a location reached by a lift truck, as NFPA 70 376.12 and 378.12 require, and a nonmetallic trough shall not be installed where it is subject to physical damage of any degree.
−## Wireways and auxiliary gutters installed in corrosive atmospheres shall be NEMA Type 4X stainless steel or fiberglass.
+### A trough installed where the atmosphere carries salt, chemical vapor, hydrogen sulfide, chlorine, or another corrosive agent, including a coastal site, a wastewater facility, a chemical process area, and a food-processing wash-down area, shall be of a material and finish the manufacturer states in writing are suitable for that atmosphere, and shall carry the enclosure type the Enclosure Type article requires.
−## Troughs installed in mechanical rooms or in proximity to plumbing subject to leaks or condensation shall not be NEMA Type 1.
+### A trough installed in a space used for environmental air shall be a metal wireway with a metal cover, as NFPA 70 300.22(C) permits, and a nonmetallic trough shall not be installed in that space.
+### A trough shall not be installed in a hazardous classified location except where [[sync/electrical-hazardous-locations]] and the article of NFPA 70 governing that location permit the trough and its fittings for the classification, and where the routing shown on the drawings passes through such a location the Contractor shall report the conflict to the Engineer of Record before the trough is ordered.
+
+### A trough shall not be installed concealed within a wall, a floor, or a ceiling, except where it passes transversely through a wall with the conductors accessible on both sides of the wall, as NFPA 70 376.10 and 378.10 permit.
+
+### A wireway is reached again after it is installed, which is the reason to use one, and a run buried in a wall or above an inaccessible ceiling has given that up while keeping the fill limits and support rules written for an accessible trough; the code permits only the pass-through, where the cover on each side of the wall can still be opened. {note}
+
+## Ambient Temperature and Sunlight {toc}
+
+### A nonmetallic trough installed outdoors, or in a space that follows the outdoor temperature, shall be listed for an ambient temperature range that includes [[parameter: site-ambient-temperature-minimum]] and [[parameter: site-ambient-temperature-maximum]], as NFPA 70 378.12 requires.
+
+### A nonmetallic trough installed where it is exposed to direct sunlight shall be listed and marked as sunlight resistant.
+
+### A nonmetallic trough shall not be installed where the conductors it carries have an insulation temperature rating above the temperature for which the trough is listed, and the fill calculation shall state the insulation type of the conductors in each nonmetallic run.
+
+### A polyvinyl chloride trough softens as it approaches its listed temperature and becomes brittle below it, grows and shrinks between the two with a coefficient several times that of steel, and chalks and cracks under ultraviolet exposure unless the resin carries an inhibitor; a conductor rated 90 °C running at its rated temperature in a trough listed for 75 °C warms the trough past its listing from the inside. These are the conditions the code names, and each is a question the site answers, which is why the ambient limits are written against the site temperatures rather than a fixed value. {note}
+
+## Seismic Restraint {toc}
+
+### The seismic restraint required for the supports of each run shall be as indicated in the datasheet.
+
```datasheet
−label: NEMA enclosure type
−type: radio
+label: Seismic Restraint Requirement
+type: select
+derived: "[[parameter: seismic-design-category]] and the component importance factor assigned to the trough under ASCE 7 Chapter 13"
options:
− - Type 1 (indoor, general purpose)
− - Type 3R (outdoor, rain-tight)
− - Type 4 (watertight)
− - Type 4X (watertight, corrosion-resistant)
− - Type 12 (dust-tight industrial)
−default: Type 1 (indoor, general purpose)
+ - "Not required"
+ - "Restraint of the supports per ASCE 7 Chapter 13"
+default: derived
```
+### Whether a run must be restrained follows from the seismic design category and from the importance factor the code assigns to the loads the run serves, so the field carries the consequence of those inputs rather than a preference; a run feeding a fire pump, egress lighting, or a load a Risk Category IV facility depends on carries the higher importance factor and is restrained in a category where an ordinary run is not, and ASCE 7 Chapter 13 exempts a trapeze-supported run below a weight per foot and a drop length that a small wireway often satisfies. {note}
+
+### Where seismic restraint is required, it shall be designed and installed in accordance with the seismic provisions of [[parameter: adopted-building-code]], ASCE 7 Chapter 13, and [[sync/vibration-isolation-and-seismic-restraint]], and the restraint shall attach to the support or the trough only at the points the manufacturer designates for it.
+
+### Where seismic restraint is required on a nonmetallic run, the restraint shall be placed so that it does not prevent the movement the expansion fittings are furnished to absorb, and the run shall be braced on one side only of each expansion fitting.
+
+# Trough Type and Classification {toc}
+
+## Trough Type {toc}
+
+### The trough type of each run shall be as indicated in the datasheet.
+
```datasheet
−label: Installed-location ambient
−type: radio
+label: Trough Type
+type: select
options:
− - Indoor, dry electrical/equipment room
− - Indoor, damp or industrial process area
− - Outdoor, exposed to weather
− - Corrosive or washdown environment
−default: Indoor, dry electrical/equipment room
+ - "Metal wireway, hinged cover"
+ - "Metal wireway, screw cover"
+ - "Nonmetallic wireway"
+ - "Auxiliary gutter"
```
−# Construction and Materials {toc}
+### A hinged-cover metal wireway opens along its full length without removing a part, so conductors are laid in from the side and a run next to a switchboard or a motor control center is opened again every time a circuit is added, which is what the lineup wireway in an electrical room is used for; a screw-cover metal wireway carries a lift-off cover held by captive screws, costs less per foot, holds its cover against vibration and against a hand that bumps it, and is the construction the Type 3R, Type 4, and Type 12 troughs are built as, since a gasketed hinge is harder to make than a gasketed flange; a nonmetallic wireway resists the atmosphere that attacks painted or galvanized steel, carries no fault current and so needs an equipment grounding conductor inside it, is limited to 3 ft support intervals unless listed for more, cannot be used in a plenum or where it is subject to physical damage, and grows and shrinks with temperature enough to need expansion fittings; an auxiliary gutter is a metal or nonmetallic trough of any of these constructions used to extend the wiring space of the equipment it is bolted to, limited to 30 ft beyond that equipment, and chosen where feeders are to be spliced, tapped, or redistributed at the equipment rather than carried past it. A project with a lineup wireway in the electrical room and a gutter above a meter center uses two types, and the type of each run is set where the run is scheduled. Neither of the two metal covers is distinctly the norm across projects, so the field asserts no default. {note}
−## Construction material is the primary durability decision and is driven by the installed environment and by mechanical exposure, not by cost alone. {note}
+### Where a project uses more than one trough type, the type of each run shall be as indicated on [[drawing: the electrical plans and equipment elevations]], and the datasheet selection shall apply to every run the drawings do not classify otherwise.
−## Steel construction (painted or galvanized) is the standard for indoor and most outdoor work; nonmetallic PVC suits mildly corrosive or nonconductive-requirement areas at smaller sizes; fiberglass suits aggressive corrosive environments where metal would degrade. {note}
+## Classification of Each Run {toc}
−## Metal wireways and gutters shall be fabricated from sheet steel with a corrosion-resistant finish, either factory paint over phosphate pretreatment or hot-dip galvanizing.
+### Each run shall be classified on the shop drawings as a wireway or as an auxiliary gutter, and the fill, the support interval, the length limit, and the ampacity adjustment rule applied to the run shall be those of the NFPA 70 article governing that classification.
−## Nonmetallic wireways shall be rigid PVC or fiberglass reinforced polyester listed under NEC Article 378.
+### A run shall be classified as an auxiliary gutter only where it supplements the wiring space of switchgear, a switchboard, a panelboard, a meter center, a motor control center, or a similar point of the wiring system, and a run that carries conductors from one piece of equipment to another shall be classified as a wireway.
−## Nonmetallic wireways shall include a separate equipment grounding conductor, because the nonmetallic enclosure cannot serve as the equipment grounding path.
+### An auxiliary gutter shall not extend more than 30 ft beyond the equipment it supplements, as NFPA 70 366.12 requires, and a run that must extend farther shall be classified and installed as a wireway for its full length.
−## Interior surfaces and all edges over which conductors pass shall be free of burrs and sharp edges that could damage conductor insulation.
+### An auxiliary gutter shall not enclose a switch, an overcurrent device, an appliance, or other equipment, as NFPA 70 366.12 requires.
+### The 30 ft limit is what separates a gutter from a raceway: within it, the trough is treated as part of the equipment it is bolted to, with the equipment's wiring space rules for bending and the gutter's own rules for support and fill; beyond it, the trough is carrying conductors between points and the raceway article applies. The gutter article never permitted a device inside the trough because a device needs the working space, the dead front, and the barriers that the equipment enclosure furnishes and the trough does not. {note}
+
+## Voltage Rating {toc}
+
+### The voltage rating of the trough shall be as indicated in the datasheet, and shall equal or exceed the system voltage of the conductors it encloses.
+
```datasheet
−label: Construction material
−type: radio
+label: Voltage Rating
+type: range
+unit: V
options:
− - Steel, ANSI 61 gray painted
− - Steel, hot-dip galvanized
− - Stainless steel
− - PVC (nonmetallic)
− - Fiberglass (FRP, nonmetallic)
−default: Steel, ANSI 61 gray painted
+ min: 600
+ max: 1000
+ setpoints: [600, 1000]
+default: 600
+constraint: min
```
+### A UL 870 trough is listed at 600 V, which covers every system through 600 V, and that is the rating on nearly every project; a trough listed at 1000 V is built with the same sheet metal and a different spacing at the joints and is furnished where the conductors are the 1000 V direct-current circuits of a photovoltaic or energy storage system, since a 600 V trough cannot enclose them. {note}
+
+# Trough Construction {toc}
+
+## Trough Material {toc}
+
+### The trough material shall be as indicated in the datasheet.
+
```datasheet
−label: Finish / coating
+label: Trough Material
type: select
options:
− - ANSI 61 gray paint
− - Powder coat
− - Hot-dip galvanized
− - Stainless (no coating)
− - Fiberglass (integral color)
−default: ANSI 61 gray paint
+ - "Steel"
+ - "Type 304 stainless steel"
+ - "Type 316 stainless steel"
+ - "Aluminum"
+ - "Rigid polyvinyl chloride"
+ - "Fiberglass-reinforced polyester"
+default: "Steel"
```
−## Voltage Rating {toc}
+### Steel is the material every indoor trough and most outdoor troughs are made of, in a painted or galvanized sheet, and it serves every enclosure type in a non-corrosive atmosphere, which is why it is the default; Type 304 stainless steel holds up where the atmosphere carries moisture and mild chemicals and where the trough is washed down, and Type 316 holds up where chlorides are present, at a cost several times that of painted steel; aluminum weighs about a third of steel for the same section, resists the atmosphere that rusts bare steel, and is attacked by the alkali in wet concrete and by chlorides, so it is chosen for a long outdoor run on a light structure and not for a coastal site; rigid polyvinyl chloride and fiberglass-reinforced polyester carry no fault current, hold up where the corrodent attacks stainless steel, and are the materials a nonmetallic wireway is made of, with fiberglass holding its shape at a higher temperature and over a longer unsupported span than polyvinyl chloride. {note}
−### Standard wireways and auxiliary gutters are rated 600 V; products listed for 1000 V are available for 1000 V distribution systems and shall be specified where the system voltage exceeds 600 V.
+### Where a nonmetallic wireway is selected under Trough Type, the trough material shall be rigid polyvinyl chloride or fiberglass-reinforced polyester, and where a metal trough is selected the material shall be steel, stainless steel, or aluminum.
−### The trough voltage rating shall equal or exceed the nominal system voltage of the conductors it encloses.
+### A steel trough shall be formed from sheet steel of not less than the thickness UL 870 requires for the trough dimensions, galvanized to ASTM A653 or finished as the Finish article requires so that no bare steel is exposed inside or outside the trough.
−```datasheet
−label: Voltage rating
−type: radio
−options:
− - 600 V
− - 1000 V
−default: 600 V
−unit: V
−```
+### A stainless steel trough shall be formed from sheet conforming to ASTM A240 of the type selected, with the joint hardware, the cover screws, and the hinge pins of stainless steel of the same type.
−## Cross-Sectional Size {toc}
+### An aluminum trough shall not be installed in direct contact with concrete, masonry, or plaster, and shall be separated from a steel support by an isolating washer or a coating so that no dissimilar-metal contact is left in a wet location.
−### The interior cross-section shall be sized so that the conductor fill does not exceed the limit set by the governing NEC article for the segment classification. {note}
+### A nonmetallic trough shall carry an equipment grounding conductor inside it, as NFPA 70 378.60 and 366.60 require.
−### Specifying a cross-section without also specifying section length and a fittings bill of material leads to quantity RFIs; the schedule shall give width, height, lengths, and fittings together.
+### The interior surfaces of every trough and fitting, and every edge over which a conductor passes, shall be smooth and rounded, free of burrs, with no screw, rivet, or bolt projecting into the conductor space, as NFPA 70 376.100 and 366.100 require.
−### The trough cross-section shall be selected so that the design conductor fill does not exceed 20% in a wireway, or 20% conductors-only (75% with splices and taps) in an auxiliary gutter.
+## Enclosure Type {toc}
−### Cross-section size shall be coordinated with the BIM/coordination model, because wide low-profile troughs commonly conflict with ductwork, piping, and cable tray at shared ceiling elevations.
+### The enclosure type shall be as indicated in the datasheet.
```datasheet
−label: Cross-sectional size (W x H)
+label: Enclosure Type per NEMA 250
type: select
options:
− - 2 x 2 in.
− - 4 x 4 in.
− - 4 x 6 in.
− - 4 x 8 in.
− - 6 x 6 in.
− - 6 x 8 in.
− - 6 x 10 in.
− - 8 x 8 in.
− - 8 x 10 in.
− - 8 x 12 in.
− - 10 x 10 in.
− - 12 x 12 in.
−default: 6 x 6 in.
+ - "Type 1"
+ - "Type 3R"
+ - "Type 4"
+ - "Type 4X"
+ - "Type 12"
+default: "Type 1"
```
+### A dry electrical room or equipment space is where a trough sits on most projects, which is why Type 1 is the default; Type 3R sheds rain and is built with a drip shield at the cover and drain openings at the bottom, and it is the type a trough between two outdoor enclosures or along an exterior wall carries; Type 4 is gasketed against hose-directed water and is the type a trough in a wash-down area carries; Type 4X is Type 4 in a material that resists corrosion, and it is the type a trough in a corrosive atmosphere carries; Type 12 is gasketed against dust, lint, and dripping oil and is the type a trough on a plant floor, in a machine shop, or in a textile or woodworking area carries. The gasketed types are built as screw-cover troughs, so a Type 4, 4X, or 12 selection and a hinged cover are not both available from every series. {note}
+
+### The trough shall comply with UL 50 and, for a type other than Type 1, with UL 50E and NEMA 250 for the type selected, and the type shall be marked on the trough.
+
+### A trough installed outdoors or in a wet location shall have an enclosure of Type 3R, Type 4, or Type 4X.
+
+### A trough installed where it is subject to hose-directed water or wash-down shall have an enclosure of Type 4 or Type 4X.
+
+### A trough installed where the atmosphere carries a corrosive agent named in the Installed Locations article shall have a Type 4X enclosure.
+
+### A trough installed indoors where airborne dust, lint, fibers, or dripping non-corrosive liquid accumulate shall have an enclosure of Type 12, Type 4, or Type 4X.
+
+### Where a type higher than the datasheet selection is required by the clauses of this article for the installed location, the higher type shall be furnished for that run and the conflict reported to the Engineer of Record before the trough is ordered.
+
+### Every fitting, end plate, equipment connector, and expansion fitting in a run shall carry the same enclosure type as the straight sections, and a Type 3R, 4, 4X, or 12 run shall be entered only with hubs or fittings listed for that type.
+
+### An opening cut in the field in a Type 3R, 4, 4X, or 12 trough other than at a location and by a method the listing permits removes the environmental rating, and the rework is charged to the party that made the cut. {note}
+
+## Finish {toc}
+
+### The finish of a metal trough shall be as indicated in the datasheet.
+
```datasheet
−label: Section length
+label: Metal Trough Finish
type: select
options:
− - 24 in.
− - 36 in.
− - 48 in.
− - 60 in.
− - 72 in.
−default: 36 in.
−unit: in.
+ - "ANSI 61 light gray paint over galvanized or phosphated steel"
+ - "ANSI 49 medium gray paint over galvanized or phosphated steel"
+ - "Hot-dip galvanized after fabrication"
+ - "Galvanized sheet, unpainted"
+ - "Mill finish, unpainted"
+ - "Custom color matched to a sample furnished by the Owner"
+default: "ANSI 61 light gray paint over galvanized or phosphated steel"
```
−## Cover Type {toc}
+### ANSI 61 gray is the finish the switchboards, panelboards, and motor control centers on a project are painted, and a trough that adjoins them is usually painted to match, which is why it is the default; ANSI 49 is the darker gray some Owners standardize on; a trough hot-dip galvanized after fabrication carries zinc over every cut edge and weld and is the finish of a steel trough installed outdoors or in a damp industrial space where a scratch through paint would rust; unpainted galvanized sheet is what a Type 1 trough in a ceiling space nobody sees is often ordered as, and it costs least; a mill finish is what a stainless steel or an aluminum trough is furnished with, since neither needs a coating; a custom color is chosen where the run is exposed in a finished space or where the Owner color-codes the system it serves. {note}
−### Cover style governs how conductors are installed and how readily splices and taps can be reached for inspection and future work. {note}
+### A painted trough shall carry a baked powder coat or enamel finish over a galvanized or phosphate-pretreated steel sheet, applied before assembly so that the inside of the trough and the inside of the cover are finished.
−### Lay-in (hinged) covers allow conductors to be laid into the trough from the side and are preferred for equipment lineups with frequent additions; screw covers and lift-off covers suit fixed runs and locations requiring tamper resistance. {note}
+### A hot-dip galvanized trough shall be galvanized after fabrication to ASTM A123, and the joint hardware and cover screws shall be galvanized or stainless steel.
−### Covers at splice and tap points shall be removable or hinged to provide the access required by NEC 376.56 (wireways) or 366.56 (auxiliary gutters).
+### Where paint, galvanizing, or an anodic film covers a bonding surface at a joint, the joint hardware shall be of a type the listing recognizes to penetrate the finish and make the bonding connection, or the finish shall be removed at the contact surface before the joint is made.
+### A nonmetallic trough shall be furnished in the manufacturer's standard integral color, and the color shall be stated in the product data.
+
+## Covers {toc}
+
+### The cover shall close the trough over its full length and shall be held by hinges and latches, by captive screws, or by both, so that no cover fastener is loose when the cover is open.
+
+### A screw cover shall be held by captive screws at intervals not exceeding the interval the listing requires for the enclosure type, and a hinged cover shall be held closed by a latch or a captive screw at each end and at intervals not exceeding 4 ft between.
+
+### The cover of a Type 3R, 4, 4X, or 12 trough shall carry the gasket the listing requires for the type, bonded or retained to the cover so that it stays in place when the cover is removed.
+
+### A trough installed where the cover would open downward shall have a cover that is hinged or that is held by a fastener at every point, so that an open cover or a removed cover does not fall into the working space.
+
+### A trough shall be installed so that its cover is accessible for its full length after the installation is complete, and the cover of a trough mounted overhead shall be on the side or on the bottom where a top cover could not be opened.
+
+## Knockouts {toc}
+
+### The knockout arrangement of the trough shall be as indicated in the datasheet.
+
```datasheet
−label: Cover type
+label: Knockouts
type: radio
options:
− - Hinged (lay-in)
− - Screw cover
− - Lift-off cover
−default: Hinged (lay-in)
+ - "No knockouts, openings field-cut with a listed punch"
+ - "Factory concentric knockouts on the sides and bottom"
```
−# Conductor Fill and Ampacity {toc}
+### A trough with no knockouts is entered where the conduits land, by a punch that cuts a round opening the hub or connector fits, and it keeps the enclosure type since no knockout ring is left loose; a trough with factory knockouts is entered faster at the sizes and spacings the factory chose, and where a knockout is not where a conduit lands the opening is field-cut anyway. Factory knockouts are furnished only in a Type 1 or a Type 3R trough, since a knockout in a gasketed trough breaks the type, and whether an Owner wants them in a Type 1 run depends on how many conduits enter and whether the run will be entered again later. Neither is distinctly the norm, so the field asserts no default. {note}
−## Conductor fill and ampacity derating are the two calculations most often misapplied on wireway and gutter work, and they differ by classification; getting the classification right is therefore a precondition to getting the fill right. {note}
+### A field-cut opening shall be made with a punch or a hole saw sized for the fitting that enters it, shall be deburred, and shall be made only in the trough wall the manufacturer designates for conduit entry.
−## In a wireway (Article 376/378), the sum of the cross-sectional areas of all contained conductors shall not exceed 20% of the interior cross-sectional area of the wireway.
+### Every knockout removed and every opening cut that is not used shall be closed with a listed closure plate or plug carrying the enclosure type of the trough.
−## In an auxiliary gutter (Article 366), conductors alone shall not exceed 20% of the interior cross-sectional area, and conductors together with splices and taps shall not exceed 75%.
+## Cross-Section {toc}
−## The design fill target should not exceed 15% for wireways and 50% for auxiliary gutters with splices, to preserve margin for future conductor additions.
+### The width and the height of the trough in each run shall be as indicated in the datasheet.
−## Where more than 30 current-carrying conductors occupy any cross-section of a wireway or auxiliary gutter, the ampacity adjustment factors of NEC Table 310.15(C)(1) shall be applied.
+```datasheet
+label: Trough Cross-Section (width × height)
+type: text
+drawing_ref: "the electrical plans and equipment elevations"
+default: deferred
+```
−## At 40 current-carrying conductors in a single cross-section, the Table 310.15(C)(1) adjustment factor is 50%, which halves allowable ampacity; this derating is frequently missed in long equipment lineups carrying many grouped branch and control circuits. {note}
+### The cross-section is a project quantity: it is set by the conductors the fill calculation puts in the fullest section of the run, by the bending space the conductors need where they deflect, by the wiring space of the equipment the run adjoins, and by the clearance available where the run passes under ductwork, piping, and cable tray at a shared elevation, so it is scheduled on the drawings for each run rather than selected once for the project. {note}
−## Conductors that pass through partitions or that leave the wireway or gutter shall be protected by smooth rounded bushings or grommets in accordance with NEC 376.56 / 366.56.
+### The cross-section of each run shall be not less than the size the conductor fill calculation requires for the fullest cross-section of the run, and where the drawings schedule a smaller trough the Contractor shall report the conflict to the Engineer of Record before the trough is ordered.
−```datasheet
−label: Design conductor fill target
−type: range
−unit: "%"
−min: 10
−max: 75
−step: 5
−default: 15
−```
+### Where conductors are deflected within a trough, at an elbow, a tee, or an entry, the trough dimensions at that point shall provide the wire bending space NFPA 70 312.6(A) requires for the largest conductor deflected, as NFPA 70 376.23, 378.23, and 366.58 require.
+### Where a trough is used as a pull box for conductors 4 AWG and larger, the distance between the raceway entries through which the conductors are pulled shall comply with NFPA 70 314.28(A), as NFPA 70 376.23, 378.23, and 366.58 require.
+
+# Conductor Fill and Ampacity {toc}
+
+## Conductor Fill {toc}
+
+### The sum of the cross-sectional areas of all conductors in any cross-section of a run, including the insulation, shall not exceed the percentage of the interior cross-sectional area of the trough indicated in the datasheet, and in no case shall it exceed 20% as NFPA 70 376.22, 378.22, and 366.22 require.
+
```datasheet
−label: Current-carrying conductor count (per cross-section)
+label: Design Conductor Fill
type: range
−unit: conductors
−min: 3
−max: 60
−step: 1
+unit: '%'
+options:
+ min: 5
+ max: 20
+ step: 5
default: 20
+constraint: max
```
+### The 20% limit of the code is what nearly every project specifies, and a run filled to it still has four fifths of its area open, which is the margin the lay-in construction trades on; a lower design fill is written where the Owner expects to add circuits to the run through the life of the installation and wants the trough sized for them at the start, at the cost of a larger trough on day one. {note}
+
+### At any point where conductors are spliced or tapped, the conductors together with the splices and taps shall not fill more than 75% of the cross-sectional area at that point, as NFPA 70 376.56, 378.56, and 366.56 require.
+
+### Conductors of a signaling circuit, and the control conductors between a motor and its starter that carry current only during starting, shall be counted in the fill but shall not be counted as current-carrying conductors.
+
+## Ampacity Adjustment {toc}
+
+### Where more than 30 current-carrying conductors occupy any cross-section of a metal wireway, a nonmetallic wireway, or a sheet metal auxiliary gutter, the ampacity of every conductor in that cross-section shall be adjusted in accordance with [[sync/conductors-and-cables]] for the number of current-carrying conductors present, as NFPA 70 376.22(B), 378.22, and 366.23(A) require, and the fill calculation shall state the count at the fullest cross-section of every run.
+
+### In a nonmetallic auxiliary gutter the ampacity adjustment factors shall be applied to the current-carrying conductors at every cross-section, with no 30-conductor threshold, as NFPA 70 366.23(B) requires.
+
+### A metal trough radiates the heat its conductors generate and the code treats it as open air up to 30 current-carrying conductors, which is the count at which the bundle in the trough begins to behave as a bundle in a raceway; a nonmetallic trough holds its heat, so the gutter article applies the raceway rule from the first conductor. A lineup wireway carrying every branch circuit from a panelboard passes 30 conductors sooner than it looks, and the conductor that was sized without the adjustment is the one that runs hot. {note}
+
+### Where the adjustment reduces the ampacity of a conductor below its load, the Contractor shall report the condition to the Engineer of Record before the conductors are pulled, and the conductors shall be resized, the run split, or the trough enlarged as the Engineer of Record directs, at no change in contract sum where the condition results from a conductor count the Contractor added.
+
+## Splices and Taps {toc}
+
+### The method by which conductors are spliced and tapped within a trough shall be as indicated in the datasheet.
+
```datasheet
−label: Ampacity adjustment applied (Table 310.15(C)(1))
−type: radio
+label: Splice and Tap Method Within the Trough
+type: select
options:
− - None required (3 CCC or fewer)
− - 80% (4-6 CCC)
− - 70% (7-9 CCC)
− - 50% (10-20 CCC)
− - 45% (21-30 CCC)
− - 40% (31-40 CCC)
− - 50% (>40 CCC)
−default: None required (3 CCC or fewer)
+ - "Listed power distribution blocks"
+ - "Listed splice and tap connectors insulated to the conductor rating"
+ - "No splices or taps within the trough"
```
−# Fittings {toc}
+### A power distribution block is a listed block with a line terminal and several load terminals, mounted in the trough, that lets one feeder be split into several without a splice on the conductor, and it is what an auxiliary gutter above a meter center or a switchboard is built around; a splice or tap connector joins conductors directly and is insulated after it is made, which costs less than a block, takes more room, and is what a wireway carrying a few circuits is tapped with; a run with no splices or taps is a pull-through, chosen where the Owner wants every connection inside a device enclosure where it can be found, inspected, and labeled with the equipment. Which of these a project wants depends on whether the run is a gutter distributing feeders or a wireway carrying circuits, and on the Owner's maintenance practice, so the field asserts no default. {note}
−## Fittings complete the routing geometry of a wireway or gutter system and shall be listed components of the same product family as the straight sections to ensure dimensional and finish compatibility.
+### A splice or tap shall be made only where the cover makes it accessible after the installation is complete, and the connector and its insulation shall comply with [[sync/conductors-and-cables]].
−## Direction changes, intersections, size transitions, and terminations shall be made with manufactured fittings matching the trough material, size, and NEMA type.
+### A power distribution block installed in a trough shall be listed for the use, shall be mounted so that the wire bending space of NFPA 70 312.6(B) is provided at every terminal, shall leave no uninsulated live part exposed within the trough whether or not the cover is in place, and shall be arranged so that its terminals remain accessible with the conductors in place, as NFPA 70 376.56(B) requires.
−## Fittings shall include, as required by the layout, elbows (30°, 45°, 90°), tee fittings, cross fittings, size reducers, end caps, flanged couplings, and expansion fittings.
+### A tap from conductors in an auxiliary gutter shall be identified at the tap with the circuit or the equipment it supplies and shall be protected by an overcurrent device as NFPA 70 240.21 and 366.56 require.
−## Field-cut openings shall not be used in place of manufactured reducers or fittings where a listed fitting is available for the transition.
+### A tap made from a bare conductor in an auxiliary gutter shall leave the gutter opposite its terminal connection and shall not be brought into contact with an uninsulated current-carrying part of opposite polarity, as NFPA 70 366.56 requires.
+### Where conductors of a Class 2, Class 3, or communications circuit share a trough with power conductors, a barrier of the trough series shall separate them, or the circuit shall be installed in a separate trough, as the article of NFPA 70 governing that circuit requires.
+
+# Fittings {toc}
+
+## Fitting Kinds {toc}
+
+### Every change of direction, branch, size transition, and termination in a run shall be made with a fitting of the same series, enclosure type, and listing as the straight sections, and the kinds of fitting furnished where the routing requires them shall be as indicated in the datasheet.
+
```datasheet
−label: Fittings required (select all that apply)
+label: Fittings Furnished Where the Routing Requires Them
type: checkbox
options:
− - 90° elbow
− - 45° elbow
− - 30° elbow
− - Tee
− - Cross
− - Reducer
− - End cap / closure
− - Flanged coupling
− - Expansion fitting
+ - "Elbows, 90° and 45°"
+ - "Tees"
+ - "Crosses"
+ - "Reducers"
+ - "Adjustable and telescoping sections"
+ - "Flanged equipment connectors and panel adapters"
+ - "End plates"
+ - "Hanger and wall-mount brackets"
+ - "Expansion fittings"
+ - "Internal barriers"
default:
− - 90° elbow
− - Tee
− - End cap / closure
− - Flanged coupling
+ - "Elbows, 90° and 45°"
+ - "Tees"
+ - "Reducers"
+ - "Adjustable and telescoping sections"
+ - "Flanged equipment connectors and panel adapters"
+ - "End plates"
+ - "Hanger and wall-mount brackets"
+constraint: all_of
```
+### A field-fabricated fitting, a field-cut section joined with substitute hardware, or a fitting from another series shall not be used where a listed fitting of the series is available for the transition.
+
+### An adjustable or telescoping section shall be used to close the last dimension of a run between two fixed points, and a straight section shall not be cut to length in the field except where the manufacturer's instructions permit a cut at a point that keeps the joint flange and the bonding connection.
+
+### A reducer shall change the cross-section only at a point where the fill calculation shows the smaller trough carries the conductors beyond it within the fill limit.
+
+## End Plates and Closures {toc}
+
+### Every dead end of a run shall be closed with an end plate of the same series and enclosure type, as NFPA 70 376.58 and 378.58 require, and no run shall be energized with an open end.
+
+### Where a run is to be extended in the future, the end plate at the extension end shall be removable, and the end shall be located as indicated on [[drawing: the electrical plans and equipment elevations]].
+
## Expansion Fittings {toc}
−### Nonmetallic wireways expand and contract significantly more than steel and require more frequent expansion fittings to prevent buckling or joint failure. {note}
+### An expansion fitting of the same series shall be furnished in every straight run of nonmetallic trough where the length change calculated from the manufacturer's published coefficient over the difference between the installation temperature and the extremes of [[parameter: site-ambient-temperature-minimum]] and [[parameter: site-ambient-temperature-maximum]] for an outdoor run, or the temperature range of the space for an indoor run, is 1/4 in. or more, as NFPA 70 378.44 and 366.44 require.
−### Long straight runs subject to thermal cycling shall be provided with expansion fittings.
+### An expansion fitting shall be furnished where any run crosses a building expansion joint shown on [[drawing: the structural framing plans]], located at the joint, and the supports on each side of the fitting shall allow the movement the fitting is furnished to absorb.
−### Expansion fittings shall be provided in nonmetallic wireway runs at intervals not exceeding the manufacturer's recommendation, approximately every 10 ft (3 m) where not otherwise specified.
+### Where a metal trough run exceeds the length at which the manufacturer's instructions call for an expansion fitting, the fitting shall be furnished at the interval the instructions state.
−```datasheet
−label: Expansion fittings provided
−type: radio
−options:
− - Not required (short metal run)
− - Provided per thermal calculation (metal)
− - Provided per manufacturer interval (nonmetallic)
−default: Not required (short metal run)
−```
+### A polyvinyl chloride trough grows about 3 1/2 in. per 100 ft over a 100 °F change, a fiberglass trough about a fifth of that, and a steel trough about two thirds of an inch; the code writes the rule for the nonmetallic trough because a straight run of it that is pinned at both ends buckles between its supports in summer and pulls its joints open in winter, while a steel run of the same length carries the stress into its joints without showing it until the bonding connection at a joint has worked loose. {note}
−# Grounding and Bonding {toc}
+# Bonding Continuity {toc}
−## Metal wireways and auxiliary gutters serve as part of the equipment grounding path only if the metal-to-metal continuity across every joint is maintained, which paint and plating at section joints can interrupt. {note}
+## A metal trough shall be electrically and mechanically continuous across every joint, fitting, and equipment connector, so that the assembly provides a continuous equipment grounding path at every point along its length, as NFPA 70 376.100 and 366.100 require.
−## Section joints shall be bonded so that the assembly provides a continuous, low-impedance equipment grounding path in accordance with NEC 376.70 and the project [[sync/grounding-and-bonding]] requirements.
+## Each joint shall be made with the bonding hardware the listing furnishes for the joint, and where the finish is not penetrated by that hardware a bonding jumper listed for the purpose shall be installed across the joint.
−## Bonding jumpers shall be installed across joints where paint, plating, or gasketing would otherwise interrupt metal continuity.
+## Every metal trough and every metal auxiliary gutter shall be bonded to the equipment grounding conductor of the largest circuit it contains, and where the trough contains service conductors it shall be bonded by the means NFPA 70 250.92 recognizes, as [[sync/grounding-and-bonding]] requires.
−## Nonmetallic wireways shall contain a separate equipment grounding conductor sized per NEC 250.122 for the largest circuit within the trough.
+## Where a raceway or cable leaves a wireway, the extension shall be made with a wiring method that includes an equipment grounding conductor or a metal raceway that serves as one, and where a separate equipment grounding conductor is used its connection to the trough shall be made with a listed terminal, as NFPA 70 376.70 and 378.70 require.
−## The equipment grounding path of the installed assembly shall be field-verified for continuity in accordance with NEC 250.96.
+## The equipment grounding conductor in a nonmetallic trough shall be continuous through the run, shall be bonded to every metal fitting and equipment enclosure the run connects to, and shall be sized as [[sync/grounding-and-bonding]] requires for the largest circuit in the trough.
−```datasheet
−label: Equipment grounding method
−type: radio
−options:
− - Metal enclosure with bonded joints (EGC path)
− - Metal enclosure plus supplemental EGC
− - Nonmetallic enclosure with separate EGC
−default: Metal enclosure with bonded joints (EGC path)
−```
+## A painted trough joined with plain bolts through painted flanges is mechanically continuous and electrically a chain of paint films, and the fault current the trough is meant to return finds its way through whatever else touches it; the listing is what tests the joint hardware for the bonding path, which is why the hardware the listing furnishes is the hardware the joint is made with. {note}
−# Testing {toc}
+# Identification {toc}
−## Factory and field testing confirm that the assembly is electrically safe and that the grounding path is continuous before energization. {note}
+## Nameplates, warning labels, and field-applied signs on a trough or on the equipment it adjoins shall comply with [[sync/equipment-labeling]] for material, lettering, and attachment.
−## Listed assemblies shall have passed the UL 870 factory tests, including dielectric voltage-withstand, grounding path continuity, cover retention, and corrosion resistance.
+## Raceway markers on the trough, the tags on the feeders and cables passing through it, and the color coding of the conductors inside it shall comply with [[sync/electrical-identification]].
−## The installed equipment grounding conductor and bonded metal path shall be field-tested for continuity in accordance with NEC 250.96 prior to energization.
+## Each trough and fitting shall carry the manufacturer's marking of the manufacturer's name or trademark, the enclosure type, and, for a nonmetallic trough, the temperature range and the sunlight resistance for which it is listed, placed so that the marking is visible after installation, as NFPA 70 376.120, 378.120, and 366.120 require.
−## Any joint failing the continuity test shall be re-bonded and re-tested until continuity is confirmed.
+# Testing {toc}
+## Field tests shall be performed on every run after installation is complete and every cover is in place, and before the conductors in the run are energized, in accordance with ANSI/NETA ATS and [[sync/electrical-acceptance-testing]], and shall include the tests indicated in the datasheet.
+
```datasheet
−label: Field tests required
+label: Field Tests
type: checkbox
options:
− - EGC / bonded-path continuity (NEC 250.96)
− - Visual inspection of fill and access
+ - "Visual and mechanical inspection of classification, support interval, cover fastening, end plates, closure of unused openings, and fill against the calculation"
+ - "Bonding continuity from the far end of every metal run to the equipment grounding terminal of the equipment it adjoins"
+ - "Bonding continuity of the equipment grounding conductor through every nonmetallic run"
default:
− - EGC / bonded-path continuity (NEC 250.96)
− - Visual inspection of fill and access
+ - "Visual and mechanical inspection of classification, support interval, cover fastening, end plates, closure of unused openings, and fill against the calculation"
+ - "Bonding continuity from the far end of every metal run to the equipment grounding terminal of the equipment it adjoins"
+ - "Bonding continuity of the equipment grounding conductor through every nonmetallic run"
+constraint: all_of
```
+## Bonding continuity shall be measured with a low-resistance ohmmeter, and a measured resistance across any joint exceeding the value ANSI/NETA ATS states for a bolted connection, or exceeding the lowest joint on the same run by more than 50%, shall be opened, cleaned, remade with new hardware, and retested before the run is energized.
+
+## A run that fails a field test shall not be energized, the Contractor shall report the failure to the Engineer of Record within one working day with the measured values, and the cost of the correction and of every repeated test shall be borne by the Contractor.
+
+## The inspection against the fill calculation is made before the cover closes for the last time because the conductor that was added after the calculation, to pick up a circuit that was not on the schedule, is invisible once the cover is on and is the conductor that puts the run over 30 at the fullest section. {note}
+
# Installation {toc}
−## Support spacing differs by classification and material and is a code requirement, not a convenience; under-supporting a run is a common inspection failure. {note}
+## Routing and Accessibility {toc}
−## Metal wireways shall be supported horizontally at intervals not exceeding 5 ft (10 ft maximum where the wireway is designed and listed for the greater spacing), and vertically at intervals not exceeding 15 ft (NEC 376.30).
+### A trough shall be installed exposed, level or plumb, and parallel to the walls, ceiling, and equipment it runs along, with the cover side toward the working space so that the cover opens without removing another item.
−## Nonmetallic wireways shall be supported horizontally at intervals not exceeding 3 ft (10 ft maximum where listed), and vertically at intervals not exceeding 4 ft (NEC 378.30).
+### A trough shall not be routed through the working space or the dedicated electrical space of other equipment, and shall not be installed where it blocks the removal of a cover, a door, a filter, or a unit of the equipment it runs past.
−## Auxiliary gutters shall be supported at intervals not exceeding 5 ft throughout their entire length (NEC 366.30).
+### Where a trough passes through a fire-resistance-rated wall or floor, the opening around it shall be closed by a through-penetration firestop system listed for the trough as the penetrating item, installed under [[sync/firestopping]], and no joint shall be located within the wall or floor thickness.
−## An auxiliary gutter shall not extend more than 30 ft (9 m) beyond the equipment it supplements; runs exceeding 30 ft shall be reclassified and installed as a wireway raceway (NEC 366.12).
+### A trough passing through a wall shall pass through in an unbroken section, with the conductors accessible on both sides of the wall, as NFPA 70 376.10 and 378.10 require.
−## Wireways and gutters shall be installed so that covers remain accessible for the entire length to permit conductor inspection and future additions.
+### A trough shall be installed so that water that enters it drains to a point where it does not reach a splice, a tap, or a piece of equipment, and a Type 3R run shall be installed with its drain openings down and unobstructed.
−## Penetrations and openings not used shall be closed with listed closure plates to maintain the NEMA enclosure rating.
+## Supports and Spacing {toc}
−## Where a trough enters or adjoins switchgear, switchboards, panelboards, or motor control centers, the connection shall be coordinated with the equipment manufacturer's wiring space and listed couplings used; see [[sync/low-voltage-switchboards]] and [[sync/motor-control-centers]].
+### Each run shall be supported by hangers, brackets, or trapeze supports furnished or designated by the manufacturer for the series, attached to the building structure, at each end, at each joint unless the listing permits otherwise, and at intervals not exceeding the interval indicated in the datasheet for a horizontal run.
```datasheet
−label: Support method
−type: radio
+label: Horizontal Support Interval
+type: range
+unit: ft
options:
− - Ceiling trapeze hanger
− - Wall bracket
− - Floor stand / support
− - Equipment-mounted (adjoining lineup)
−default: Ceiling trapeze hanger
+ min: 3
+ max: 10
+ setpoints: [3, 4, 5, 6, 8, 10]
+default: 5
+constraint: max
```
−```datasheet
−label: Maximum horizontal support spacing
−type: select
−options:
− - 3 ft (nonmetallic wireway)
− - 5 ft (metal wireway / auxiliary gutter)
− - 10 ft (listed for greater spacing)
−default: 5 ft (metal wireway / auxiliary gutter)
−unit: ft
−```
+### NFPA 70 376.30 supports a metal wireway at each end and at intervals not exceeding 5 ft, and permits an interval up to 10 ft only where the wireway is listed for it; NFPA 70 378.30 supports a nonmetallic wireway at 3 ft unless listed for more, and never more than 10 ft; NFPA 70 366.30 supports a sheet metal auxiliary gutter at 5 ft and a nonmetallic one at 3 ft. The 5 ft interval is what nearly every metal run is supported at, which is why it is the default, and the field exists for the engineer who wants a closer interval than the code or the listing allows, for a run that carries a heavy fill, a run that will be opened and loaded often, or a run on a structure that moves. {note}
−## Routing Coordination {toc}
+### The support interval on any run shall not exceed the interval NFPA 70 permits for the classification and material of the run, nor the interval the trough is listed for, whichever is less, whatever the datasheet selects.
−### Routing, extents, and arrangement of wireway and gutter runs are location-specific and shall be taken from the drawings, not fixed by this standard. {note}
+### A vertical run shall be supported at intervals not exceeding 15 ft for a metal wireway and 4 ft for a nonmetallic wireway or a nonmetallic auxiliary gutter, with not more than one joint between supports, as NFPA 70 376.30(B), 378.30(B), and 366.30(B) require.
−### Wireway and auxiliary gutter routing shall follow the contract drawings [[drawing: wireway routing plan]].
+### A support shall bear on the trough body and not on a cover, a hinge, a joint flange, or an expansion fitting, and no support shall be attached by a fastener that projects into the conductor space.
−### Equipment lineup adjacencies and gutter extension limits shall be coordinated with the equipment elevations [[drawing: equipment lineup elevation]].
+### Supports shall be of a material or finish suitable for the exposure of the run, and a support for an outdoor, wet, or corrosive-location run shall be galvanized, stainless steel, or nonmetallic as the atmosphere requires.
+### The Contractor shall confirm with the Engineer of Record that the structure at each support carries the weight of the trough, its conductors at the design fill, and the seismic load where restraint is required, before the supports are installed.
+
+## Connections to Equipment {toc}
+
+### Where a trough adjoins switchgear, a switchboard, a panelboard, a meter center, a motor control center, or a control panel, the connection shall be made through the wiring space that equipment's manufacturer designates on its shop drawings, with a flanged connector or a panel adapter of the trough series listed for the connection, and the opening in the equipment shall be made by that equipment's manufacturer or as its listing permits.
+
+### The connection to the equipment shall keep the enclosure type of the equipment and of the trough, and a connector to a Type 3R, 4, 4X, or 12 enclosure shall be gasketed and listed for the type.
+
+### The equipment standard furnishes the opening and the wiring space on the equipment side and hands the trough to this standard; the connector between the two is the trough manufacturer's, and the flange pattern, the opening size, and the location are coordinated between the two manufacturers before either is released, because an opening cut in the field in a listed enclosure is what the equipment standards charge back. {note}
+
+### No trough shall be used to support, align, or restrain the equipment it connects to, and the equipment shall be anchored before the connector is bolted to it.
+
+### Every shipping cover, packing, and loose knockout ring shall be removed from the trough before conductors are laid in, and every cover, end plate, and closure plate shall be in place before the run is energized.
+
+## Laying In Conductors {toc}
+
+### Conductors shall be laid into the trough without crossing at a joint, with each circuit's conductors grouped together, and shall be laid so that the cover closes without bearing on a conductor.
+
+### Conductors shall be laid in and supported so that no conductor bears on an edge, a knockout, or a fastener, and where conductors leave the trough through an opening the opening shall carry a bushing or a fitting that protects the insulation.
+
+### Conductors in a vertical run shall be supported at the intervals NFPA 70 300.19 requires for the conductor size, by a support the trough manufacturer furnishes or by a cable support installed within the trough.
+
# Delivery, Storage, and Handling {toc}
−## Wireways, gutters, and fittings shall be delivered in the manufacturer's original packaging with listing labels intact.
+## Each section and fitting shall be delivered in the manufacturer's packaging with the listing marks intact and the finish protected, and shall be inspected for shipping damage at receipt.
−## Materials shall be stored indoors or under cover, protected from weather, dust, and physical damage until installation.
+## Sections and fittings shall be stored indoors in a dry space, or under cover off the ground where indoor storage is not available, protected from precipitation, condensation, and physical damage, and a nonmetallic section shall be stored out of direct sunlight and supported along its length so that it does not sag.
−## Nonmetallic and fiberglass sections shall be protected from prolonged ultraviolet exposure during storage unless rated for outdoor use.
+## A section whose finish is scratched through to bare steel shall be touched up with the manufacturer's touch-up paint before installation, and a section that is bent, dented so that the cover does not seat, or cracked shall be replaced.
# Warranty {toc}
−## The manufacturer shall warrant the wireways, auxiliary gutters, and fittings against defects in materials and workmanship for the manufacturer's standard period from the date of substantial completion.
+## The manufacturer shall warrant each trough, fitting, and cover against defects in materials and workmanship for the period indicated in the datasheet.
−## The Contractor shall correct defects in installation, including failed joint bonding and inadequate support, for the project warranty period at no cost to the Owner.
+```datasheet
+label: Manufacturer's Warranty Period
+type: range
+unit: years
+options:
+ min: 1
+ max: 5
+ setpoints: [1, 2, 3, 5]
+default: 1
+constraint: min
+```
+## One year is the manufacturer's standard term for a trough, which has no moving part but a hinge and no component that wears, and it is the term nearly every project accepts; a longer term is bought where the Owner holds every product on the project to one warranty length or where a finish in a corrosive atmosphere is the concern, and the manufacturer prices the added years into the trough. {note}
+
+## The warranty period shall commence on the date indicated in the datasheet.
+
```datasheet
−label: Warranty period
−type: radio
+label: Warranty Commencement
+type: select
options:
− - 1 year
− - 2 years
− - 5 years
−default: 1 year
+ - "Date of substantial completion"
+ - "Date of energization"
+ - "Date of shipment"
```
−# Spare Parts {toc}
+## Warranty commencement at shipment is the manufacturer's usual term, and it consumes the warranty while the sections sit in storage and the run is assembled; commencement at energization or substantial completion moves the coverage to the period the Owner is operating the run, and the manufacturer prices the added months into the trough. {note}
−## Spare covers, fittings, and closure plates allow minor field changes and repairs without a new procurement cycle. {note}
+## The Contractor shall warrant the installation, including every joint, every support, every bonding connection, and every equipment connection, for the project warranty period.
−## The Contractor shall furnish spare end caps, splice plates, and cover sections as required by the project, of the same material and NEMA type as installed.
+## A section, fitting, or cover replaced under warranty shall be warranted for the remainder of the original period or for one year from the date of replacement, whichever ends later.
+# Spare Parts {toc}
+
+## The Contractor shall deliver the spare parts indicated in the datasheet to the Owner before the runs are accepted, and shall obtain a signed receipt for them.
+
```datasheet
−label: Spare parts furnished
+label: Spare Parts to Be Furnished
type: checkbox
options:
− - Spare cover sections
− - Spare end caps / closures
− - Spare splice plates
− - Spare couplings
+ - "One cover section of each size and enclosure type installed"
+ - "One end plate of each size and enclosure type installed"
+ - "One joint hardware kit for every ten joints installed, and not fewer than two"
+ - "One closure plate of each knockout size used"
+ - "One pint of touch-up paint matching the finish"
default:
− - Spare end caps / closures
− - Spare splice plates
+ - "One end plate of each size and enclosure type installed"
+ - "One joint hardware kit for every ten joints installed, and not fewer than two"
+ - "One pint of touch-up paint matching the finish"
+constraint: all_of
```
+
+## Spare parts shall be identical to and interchangeable with the installed parts, shall be delivered in their original packaging, and shall be labeled with the trough series, the size, and the enclosure type they serve.
+
+## The spares under this standard are the parts that let a run be opened, extended, or closed again without waiting on the manufacturer's lead time: the end plate that closes a run after a section is removed, the hardware for a joint remade, and the paint for a scratch that would otherwise rust. {note}