Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Industrial Control Panels
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### The enclosure, subpanel, and all factory-installed components shall be furnished and assembled by the listed panel shop as a single listed assembly bearing one UL 508A mark.
−### Field modification that adds or relocates power-circuit components after listing shall not be performed unless the modification is made under the panel shop's listing or re-evaluated by the NRTL, because such modification can void the marked SCCR and the listing. {note}
+### Field modification that adds or relocates power-circuit components after listing shall not be performed unless the modification is made under the panel shop's listing or re-evaluated by the NRTL, because such modification can void the marked SCCR and the listing.
## Component Listings {toc}
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# Environmental and Service Conditions {toc}
−## The panel shall be suitable for continuous operation under the ambient conditions at its installed location. {note}
+## The panel shall be suitable for continuous operation under the ambient conditions at its installed location.
−## Where site conditions exceed the values selected below, notify the manufacturer so the enclosure type, thermal management, and component derating can be confirmed. {note}
−
```datasheet
label: Installed Environment
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```
+## Where site conditions exceed the values selected below, notify the manufacturer so the enclosure type, thermal management, and component derating can be confirmed. {note}
+
+## Component continuous ratings are established at a 40°C reference ambient; where the maintained internal enclosure temperature exceeds this reference, components shall be derated per their published tables.
+
```datasheet
label: Maximum Ambient Temperature
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```
+## Water and wastewater environments are routinely classified C4 or higher because of chlorine, hydrogen sulfide, and washdown exposure; enclosure material and finish shall be selected for the corrosion severity at the specific installed location rather than a facility-wide default.
+
```datasheet
label: Corrosion Severity
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```
−## Component continuous ratings are established at a 40°C reference ambient; where the maintained internal enclosure temperature exceeds this reference, components shall be derated per their published tables.
−
−## Water and wastewater environments are routinely classified C4 or higher because of chlorine, hydrogen sulfide, and washdown exposure; enclosure material and finish shall be selected for the corrosion severity at the specific installed location rather than a facility-wide default.
−
## For chemical feed rooms, headworks, and digester areas classified C5, the manufacturer shall confirm enclosure material suitability for the specific corrosive exposure and submit that confirmation with shop drawings.
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## Type Rating {toc}
−### Enclosure type rating shall be as indicated for the installed environment and shall be listed to UL 50 and UL 50E for the marked type. {note}
+### Enclosure type rating shall be as indicated for the installed environment and shall be listed to UL 50 and UL 50E for the marked type.
```datasheet
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### Fiberglass-reinforced polyester or non-metallic enclosures may be used where the environment is corrosive but the housed equipment does not require the electromagnetic shielding of a metallic enclosure.
−### Non-metallic enclosures shall not be used where the housed equipment requires a continuous metallic ground reference plane or shielding against electrical noise. {note}
+### Non-metallic enclosures shall not be used where the housed equipment requires a continuous metallic ground reference plane or shielding against electrical noise.
### Painted steel enclosures shall receive a minimum two-coat system of corrosion-resistant primer and polyester powder-coat finish with a minimum 3 mil (75 µm) total dry film thickness.
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```
−## Construction {toc}
+## Enclosure dimensions and mounting configuration shall be [[drawing: as indicated on the contract drawings]].
−### Enclosure dimensions and mounting configuration shall be [[drawing: as indicated on the contract drawings]].
−
```datasheet
label: Mounting Configuration
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```
−### Doors shall be hinged, gasketed where the type rating requires, and fitted with a three-point latching mechanism on doors exceeding 48 in. in height to maintain the gasket seal across the full door.
+## Doors shall be hinged, gasketed where the type rating requires, and fitted with a three-point latching mechanism on doors exceeding 48 in. in height to maintain the gasket seal across the full door.
−### A removable or hinged subpanel finished with a conductive or paintable surface shall be provided for mounting components; components shall not be mounted to the enclosure walls or door except for operator interface and pilot devices.
+## A removable or hinged subpanel finished with a conductive or paintable surface shall be provided for mounting components; components shall not be mounted to the enclosure walls or door except for operator interface and pilot devices.
−### Door-mounted devices shall be sealed to maintain the enclosure type rating, and conductors crossing the hinge shall be protected with a flexible hinge-wire harness or spiral wrap rated for repeated flexing.
+## Door-mounted devices shall be sealed to maintain the enclosure type rating, and conductors crossing the hinge shall be protected with a flexible hinge-wire harness or spiral wrap rated for repeated flexing.
−### Print pockets shall be provided on the inside of each door to hold the as-built wiring diagrams.
+## Print pockets shall be provided on the inside of each door to hold the as-built wiring diagrams.
# Power Distribution {toc}
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### Where the determined SCCR is below the available fault current, the rating shall be raised before fabrication by applying a current-limiting protective device, selecting higher-rated components, or applying the feeder-circuit method of Supplement SB4.3.
−### The feeder-circuit method limits the let-through energy ahead of the branch components using a current-limiting device located entirely in the feeder circuit; that device shall not be relied upon for branch-circuit protection. {note}
+### The feeder-circuit method limits the let-through energy ahead of the branch components using a current-limiting device located entirely in the feeder circuit; that device shall not be relied upon for branch-circuit protection.
### A control panel SCCR is a frequent inspection and RFI failure point; many off-the-shelf components default to 5 kA, which is below the available fault current at typical service entrances, so the determination shall be performed during design rather than assumed. {note}
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## Power and Signal Segregation {toc}
−### Power wiring and control or signal wiring shall be routed in separate wireways and shall not share a common wireway or be bundled together. {note}
+### Power wiring and control or signal wiring shall be routed in separate wireways and shall not share a common wireway or be bundled together.
### Where power and signal conductors must cross, they shall cross at right angles to minimize coupling.
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### A minimum separation of 1 in. shall be maintained between parallel runs of power wiring and signal wiring, increasing the separation where higher-energy or drive output circuits are present.
−### Variable frequency drive output conductors, where present, shall be routed in dedicated wireways or shielded cable separated from all control and signal wiring, because drive output carries high-frequency switching noise that couples readily into instrument circuits. {note}
+### Variable frequency drive output conductors, where present, shall be routed in dedicated wireways or shielded cable separated from all control and signal wiring, because drive output carries high-frequency switching noise that couples readily into instrument circuits.
## Conductors {toc}
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| Green or green with yellow stripe | Equipment grounding (protective) conductors |
−### Orange conductors shall identify every circuit that is not de-energized by the panel main disconnect, so that maintenance personnel are warned of voltage present after lockout of the main disconnect. {note}
+### Orange conductors shall identify every circuit that is not de-energized by the panel main disconnect, so that maintenance personnel are warned of voltage present after lockout of the main disconnect.
## Wire and Terminal Identification {toc}
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# Thermal Management {toc}
−## The internal enclosure temperature shall be maintained within the operating range of the housed components, which is commonly 0°C to 50°C, under the maximum external ambient and full internal heat load. {note}
+## The internal enclosure temperature shall be maintained within the operating range of the housed components, which is commonly 0°C to 50°C, under the maximum external ambient and full internal heat load.
## Heat Load {toc}
### The manufacturer shall calculate the total internal heat load as the sum of the heat dissipated by all housed components plus, for sealed enclosures, the heat transferred through the enclosure walls from the external ambient.
−### Component heat dissipation in watts shall be converted to BTU/hr by multiplying by 3.412 where the cooling equipment is rated in BTU/hr. {note}
+### Component heat dissipation in watts shall be converted to BTU/hr by multiplying by 3.412 where the cooling equipment is rated in BTU/hr.
### The thermal calculation shall account for solar heat gain on outdoor enclosures and for the reduced dissipation surface of enclosures mounted against a wall or grouped together.
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### Filtered fans with intake and exhaust vents may be used only in Type 12 indoor environments where the ambient air is clean and cool; filters shall be listed to UL 1283 and shall be accessible for replacement without opening the enclosure.
−### A filtered-fan ventilation scheme shall not be used on a Type 4, 4X, or outdoor enclosure, because it breaches the watertight and corrosion-resistant rating; sealed cooling by air-to-air heat exchanger, closed-loop air conditioner, or vortex cooler shall be used instead. {note}
+### A filtered-fan ventilation scheme shall not be used on a Type 4, 4X, or outdoor enclosure, because it breaches the watertight and corrosion-resistant rating; sealed cooling by air-to-air heat exchanger, closed-loop air conditioner, or vortex cooler shall be used instead.
### A closed-loop air conditioner shall be used where the internal heat load cannot be rejected to the ambient by a heat exchanger, such as where the external ambient approaches or exceeds the maximum allowable internal temperature.
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# Grounding and Bonding {toc}
−## A grounding terminal or bar shall be provided in the enclosure and bonded to the subpanel and to all non-current-carrying metal parts. {note}
+## A grounding terminal or bar shall be provided in the enclosure and bonded to the subpanel and to all non-current-carrying metal parts.
## The enclosure grounding terminal shall be connected to the facility grounding system per [[sync/grounding-and-bonding]].
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## A separate, insulated instrument-reference (clean) ground bar shall be provided where the housed instrumentation requires an isolated signal ground, connected to the grounding system at a single point per IEEE 518 to avoid ground loops on analog signals.
−## Shield-drain conductors for analog signal cables shall land on the instrument-reference ground bar at the single grounding point, not on the equipment grounding bar. {note}
+## Shield-drain conductors for analog signal cables shall land on the instrument-reference ground bar at the single grounding point, not on the equipment grounding bar.
# Identification {toc}
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## Factory Tests {toc}
−### The panel shop shall perform the following production tests on the completed panel before shipment: {note}
+### The panel shop shall perform the following production tests on the completed panel before shipment:
- Dielectric withstand (hipot) test of the power circuit per UL 508A
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## Field Tests {toc}
−### After installation and before placing the panel in service, the Contractor shall verify the following: {note}
+### After installation and before placing the panel in service, the Contractor shall verify the following:
- The available fault current at the installed location does not exceed the marked panel SCCR
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## A spare DC power supply shall be provided where the panel serves a critical process and loss of control power would interrupt operation.