+---
+title: Variable Refrigerant Flow (VRF) Systems
+category: Mechanical / Air Distribution
+toc_depth: 3
+description: >
+ When to use: Variable refrigerant flow (VRF/VRV) air-conditioning and heat pump systems serving commercial, institutional, and multifamily buildings, in which one or more inverter-driven condensing units circulate refrigerant through a piped network to multiple indoor fan-coil units, each metered by an electronic expansion valve. Covers heat pump (cooling-or-heating) and heat recovery (simultaneous cooling and heating) systems, air-cooled and water-source (water-cooled) condensing units, ducted and non-ducted indoor unit types, branch controllers and refrigerant selector boxes, A2L refrigerant safety and leak detection, and coordination of a dedicated outdoor air system for ventilation.
+ Not intended for: Single-zone or multi-split residential systems and packaged unitary equipment (see [[sync/split-system-air-conditioners]]); central station air handling units and dedicated outdoor air units (see [[sync/air-handling-units]] and [[sync/dedicated-outdoor-air-systems]]); chilled water plants (see [[sync/chillers]]); the refrigerant piping itself, which is specified separately (see [[sync/refrigerant-piping]]); air terminal devices, diffusers, and grilles (see [[sync/hvac-air-distribution-devices]]); building automation system head-end and network (see [[sync/building-automation-system]]); and post-installation balancing (see [[sync/testing-adjusting-and-balancing]]).
+---
+
+# Scope
+
+This specification covers variable refrigerant flow (VRF) systems, also marketed as variable refrigerant volume (VRV), in which one or more inverter-driven compressors in a condensing unit modulate refrigerant flow through a shared piping network to multiple indoor fan-coil units. Each indoor unit is metered by its own electronic expansion valve (EEV) and operates independently to satisfy the load of the zone it serves. Equipment covered includes outdoor (or indoor-installed) condensing units, indoor fan-coil units of all types, branch controllers and refrigerant selector boxes, refrigerant-side accessories, leak detection and mitigation devices, condensate management, and the system controls.
+
+A VRF system is distinguished from conventional split-system equipment by its ability to serve many zones from a single refrigerant circuit with continuously variable capacity, and by its part-load efficiency: inverter compressors and EEV-metered indoor units allow the system to track building load closely rather than cycling on and off. Heat recovery systems extend this advantage by transferring heat rejected from zones in cooling to zones calling for heating on the same circuit, delivering simultaneous heating and cooling at high efficiency.
+
+VRF equipment shall be rated and certified under ANSI/AHRI 1230 for performance. Refrigerant safety, refrigerant concentration limits, machinery room requirements, and A2L (mildly flammable) refrigerant provisions shall comply with ANSI/ASHRAE 15 and ANSI/ASHRAE 15.2. Refrigerant classification shall follow ANSI/ASHRAE 34. Electrical and refrigerant safety listing shall comply with UL 60335-2-40. Energy efficiency shall comply with ANSI/ASHRAE/IES 90.1.
+
+A VRF system delivers no outdoor air through its indoor units; the indoor units recirculate room air across a refrigerant coil only. Code-required ventilation shall therefore be provided by a separate dedicated outdoor air system (DOAS) designed in accordance with ANSI/ASHRAE 62.1 — see [[sync/dedicated-outdoor-air-systems]] and [[sync/air-handling-units]]. The refrigerant piping that connects the condensing units, branch controllers, and indoor units shall be designed, sized, and installed per [[sync/refrigerant-piping]] and the equipment manufacturer's design software; this standard governs the equipment and system, not the piping construction.
+
+The Contractor shall coordinate VRF installation with the DOAS, the building automation system per [[sync/building-automation-system]], electrical power and control wiring, condensate drainage, refrigerant leak detection and ventilation interlocks, and the structural support and seismic restraint of all units.
+
+# Referenced Standards
+
+Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited. Where conflicts exist between referenced standards, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+| Standard | Title |
+|----------|-------|
+| ANSI/AHRI 1230 (I-P) | Performance Rating of Variable Refrigerant Flow (VRF) Multi-Split Air-Conditioning and Heat Pump Equipment |
+| ANSI/AHRI 1231 (SI) | Performance Rating of Variable Refrigerant Flow (VRF) Multi-Split Air-Conditioning and Heat Pump Equipment (SI companion) |
+| ANSI/ASHRAE 15 | Safety Standard for Refrigeration Systems |
+| ANSI/ASHRAE 15.2 | Safety Standard for Refrigeration Systems in Residential and Light-Commercial Applications |
+| ANSI/ASHRAE 34 | Designation and Safety Classification of Refrigerants |
+| ANSI/ASHRAE 62.1 | Ventilation and Acceptable Indoor Air Quality |
+| ANSI/ASHRAE/IES 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings |
+| UL 60335-2-40 | Household and Similar Electrical Appliances — Particular Requirements for Electrical Heat Pumps, Air-Conditioners, and Dehumidifiers |
+| NFPA 90A | Standard for the Installation of Air-Conditioning and Ventilating Systems |
+| NFPA 70 (NEC) | National Electrical Code |
+| IMC (International Mechanical Code) | International Mechanical Code, adopted edition |
+| ASHRAE Handbook | HVAC Systems and Equipment; Fundamentals; Refrigeration |
+| EPA SNAP / AIM Act | EPA Significant New Alternatives Policy and American Innovation and Manufacturing Act refrigerant GWP rules |
+
+# Submittals
+
+## Action Submittals
+
+Contractor shall submit the following for review and acceptance prior to ordering equipment. Fabrication and procurement shall not proceed until action submittals have been reviewed and returned.
+
+- Manufacturer's product data for each condensing unit, indoor unit, branch controller, and controller, including model designation, nominal capacity, electrical data, sound data, and physical dimensions and weights
+- AHRI 1230 certified performance ratings for each system, including rated cooling and heating capacity, IEER, EER, COP, and SCHE (simultaneous cooling and heating efficiency) for heat recovery systems, at the rated and applicable part-load conditions
+- A complete system schematic (one-line refrigerant diagram) showing every condensing unit, branch controller, indoor unit, and the refrigerant piping topology, with refrigerant pipe sizes, equivalent lengths, and elevation changes
+- Manufacturer-software-generated piping design report confirming that total piping length, farthest-unit length, and elevation differences between units are within the manufacturer's published limits, and stating the calculated additional refrigerant charge
+- Refrigerant concentration calculation per ASHRAE 15 for the smallest occupied space served by each refrigerant circuit, demonstrating that the concentration in a single-fault total release does not exceed the refrigerant concentration limit (RCL), or documenting the mitigation provided
+- A2L refrigerant safety provisions, including leak detector locations and setpoints, mitigation airflow, and any interlocks, where the system uses an A2L refrigerant
+- Indoor unit schedule correlating each unit's tag to its zone, type, capacity, airflow, external static pressure (for ducted units), and electrical and condensate connections
+- Electrical load schedule with minimum circuit ampacity (MCA) and maximum overcurrent protection (MOCP) for each unit, and the transmission (control) wiring topology
+- Controls submittal including network architecture, BAS gateway or native protocol interface, point list, and sequence of operation
+- Structural support, vibration isolation, and seismic restraint details and calculations where required by the applicable building code
+- Startup and commissioning plan identifying the manufacturer-authorized field technician
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Product data for all units and controllers"
+ - "AHRI 1230 certified performance ratings"
+ - "System refrigerant one-line schematic"
+ - "Manufacturer software piping design report with charge calculation"
+ - "ASHRAE 15 refrigerant concentration (RCL) calculation"
+ - "A2L leak detection and mitigation provisions"
+ - "Indoor unit schedule"
+ - "Electrical load schedule (MCA/MOCP)"
+ - "Controls architecture, point list, and sequence of operation"
+ - "Structural, vibration, and seismic restraint details"
+ - "Startup and commissioning plan"
+default: "AHRI 1230 certified performance ratings"
+```
+
+## Closeout Submittals
+
+Contractor shall provide the following at or before substantial completion:
+
+- Operation and maintenance manuals for all equipment, organized with a table of contents
+- Manufacturer's commissioning and startup report, signed by the authorized field technician, including measured refrigerant charge, evacuation records, and pressure/leak test results
+- As-built system schematic reflecting the installed piping topology and final indoor unit assignments
+- Final refrigerant concentration calculation reflecting the actual installed charge per circuit
+- Controls point list, network address map, and final sequence of operation as commissioned
+- Refrigerant tracking documentation, including the type, total installed charge per circuit, and field-added charge, for each system
+- Warranty documentation from the manufacturer
+
+# Quality Assurance
+
+## Manufacturer Qualifications
+
+VRF equipment shall be the product of a single manufacturer that has produced VRF systems for the North American market for a minimum of five years and maintains factory technical support, replacement-parts availability, and a network of factory-authorized service technicians within the project region. All major components of a given system — condensing units, indoor units, branch controllers, and controls — shall be products of the same manufacturer and shall be designed to operate together as a certified system.
+
+## Single-System Responsibility
+
+For each refrigerant circuit, the condensing unit(s), indoor units, branch controllers, EEVs, and controls shall be furnished by or through a single manufacturer as a coordinated system. Substituting components from another manufacturer onto a VRF circuit is not acceptable, because refrigerant flow control, oil management, and capacity modulation are proprietary to each manufacturer's system and are not interoperable.
+
+## AHRI Certification
+
+Each VRF system shall be certified under the AHRI Variable Refrigerant Flow Multi-Split Air-Conditioning and Heat Pump Equipment Certification Program per ANSI/AHRI 1230. Published cooling capacity, heating capacity, IEER, EER, and COP shall bear the AHRI certification mark. Capacities and efficiencies that are catalog estimates not covered by the AHRI certification are not acceptable as the basis of compliance.
+
+## NRTL Listing
+
+All condensing units, indoor units, branch controllers, and control devices shall be listed and labeled by a Nationally Recognized Testing Laboratory (NRTL) to UL 60335-2-40. Equipment charged with an A2L refrigerant shall carry the specific UL 60335-2-40 listing applicable to mildly flammable (A2L) refrigerant equipment, including any required factory-installed mitigation features.
+
+## Installer Qualifications
+
+VRF brazing, evacuation, charging, startup, and commissioning shall be performed by technicians who have completed the equipment manufacturer's VRF training program and hold current certification. The system warranty is contingent on this requirement; the Contractor shall confirm installer certification in the submittal.
+
+## Pre-Installation Conference
+
+A pre-installation conference shall be held before beginning refrigerant piping or equipment installation, attended by the Contractor, the mechanical and controls sub-contractors, the manufacturer's representative, and the Owner's representative. The agenda shall include piping routing and support, refrigerant concentration and leak-detection provisions, DOAS coordination, controls integration, and the commissioning schedule.
+
+# Environmental and Service Conditions
+
+VRF equipment shall be selected and rated for the operating conditions at the installation site. Design conditions are [[drawing: as indicated on the mechanical schedules]]. The equipment shall operate within the following envelope without damage, derating below the scheduled capacity, or loss of function.
+
+## Outdoor Ambient Range
+
+Air-cooled condensing units shall be rated for continuous cooling operation across the project's design summer ambient and for continuous heating operation across the design winter ambient. Standard air-source units provide cooling to approximately 115°F to 122°F (46°C to 50°C) outdoor dry-bulb and heating to approximately 0°F to −13°F (−18°C to −25°C); low-ambient heating models extend heating operation lower. Where the design winter ambient is below the standard equipment rating, a low-temperature heating model or a supplemental heat source shall be provided.
+
+```datasheet
+label: Condensing Unit Installation Environment
+type: select
+options:
+ - "Outdoor — at grade on housekeeping pad"
+ - "Outdoor — rooftop on curb or rails"
+ - "Outdoor — wall- or balcony-mounted (small systems)"
+ - "Indoor — mechanical room (water-source units)"
+default: "Outdoor — rooftop on curb or rails"
+```
+
+```datasheet
+label: Design Winter Heating Ambient (lowest)
+type: range
+unit: °F
+drawing_ref: true
+options:
+ min: -25
+ max: 47
+ setpoints: [-25, -13, -4, 0, 5, 17, 32, 47]
+default: 5
+```
+
+## Low-Ambient Heating Capability
+
+Where the system provides primary heating in a cold climate, a low-ambient heating condensing unit shall be specified and the heating capacity shall be evaluated at the design winter ambient, not at the nominal rating point. VRF heating capacity falls as outdoor temperature drops, and defrost cycles further reduce net output; a unit selected on nominal capacity alone will be undersized for heating at design conditions. The selected heating capacity at the design winter ambient shall meet or exceed the building heating load.
+
+```datasheet
+label: Heating Capability Class
+type: radio
+options:
+ - "Standard heating range"
+ - "Low-ambient (cold climate) heating range"
+default: "Standard heating range"
+```
+
+## Altitude
+
+Where the project site is above 3,000 ft (914 m), condensing unit airflow and capacity shall be corrected for air density at the project elevation, and the correction shall be documented in the submittal.
+
+# System Configuration
+
+## System Type
+
+The system type determines what the system can do at any instant. A heat pump system places all indoor units on one circuit into either cooling or heating at a time; it cannot cool one zone while heating another. A heat recovery system can simultaneously cool some zones and heat others on the same circuit, transferring heat rejected by the zones in cooling to the zones in heating. Heat recovery is strongly preferred for buildings with diverse simultaneous loads — perimeter and core zones, or zones with differing solar and internal-gain exposure — because it both serves those loads and reclaims energy that a heat pump system would reject outdoors.
+
+```datasheet
+label: VRF System Type
+type: radio
+options:
+ - "Heat pump — cooling or heating, all zones on a circuit in the same mode"
+ - "Heat recovery — simultaneous cooling and heating on the same circuit"
+default: "Heat recovery — simultaneous cooling and heating on the same circuit"
+```
+
+## Condenser Heat Rejection Source
+
+Air-cooled (air-source) condensing units reject heat to outdoor air and are the most common configuration; they require outdoor installation with adequate airflow and clearance. Water-source (water-cooled) condensing units reject heat to a building water loop and are installed indoors, which suits high-rise buildings, locations with no roof or grade access, and campuses with a central condenser-water or geothermal loop. Water-source units also extend the usable ambient range, because the loop temperature is moderated by the building or the ground rather than tracking outdoor air.
+
+```datasheet
+label: Condenser Heat Rejection Source
+type: radio
+options:
+ - "Air-cooled (air-source) — heat rejected to outdoor air"
+ - "Water-source (water-cooled) — heat rejected to building water loop"
+ - "Geothermal water-source — heat rejected to ground loop"
+default: "Air-cooled (air-source) — heat rejected to outdoor air"
+```
+
+## Refrigerant Type
+
+The refrigerant determines the safety classification, the applicable code provisions, and the leak detection and concentration requirements. R-410A (A1, non-flammable) has been the industry standard but is being phased down under the EPA AIM Act and SNAP program, which restrict new equipment to refrigerants below a 700 GWP limit beginning in 2025. New VRF equipment is transitioning to A2L (mildly flammable) refrigerants — principally R-32 and R-454B — which meet the GWP limit but are classified A2L under ASHRAE 34 and therefore trigger the A2L provisions of ASHRAE 15, ASHRAE 15.2, and UL 60335-2-40. The specifier shall confirm the refrigerant offered for the selected equipment generation, because the leak detection, mitigation, and concentration requirements depend on it.
+
+```datasheet
+label: System Refrigerant
+type: radio
+options:
+ - "R-454B (A2L, mildly flammable) — current low-GWP equipment"
+ - "R-32 (A2L, mildly flammable) — current low-GWP equipment"
+ - "R-410A (A1, non-flammable) — legacy equipment where still available"
+default: "R-454B (A2L, mildly flammable) — current low-GWP equipment"
+```
+
+# Outdoor and Condensing Units
+
+## Compressors
+
+Condensing units shall employ inverter-driven (variable-speed) compressors that modulate capacity continuously to match the connected load. Where multiple compressors are provided in a unit or module, at least one shall be inverter-driven; fixed-speed compressors are acceptable only as additional staged compressors in a unit whose lead compressor is inverter-driven. Continuous inverter modulation is the basis of VRF part-load efficiency and is required; constant-speed-only condensing units are not acceptable.
+
+```datasheet
+label: Compressor Modulation
+type: radio
+options:
+ - "All-inverter (variable-speed) compressors"
+ - "Inverter lead compressor with staged fixed-speed compressor(s)"
+default: "All-inverter (variable-speed) compressors"
+```
+
+## Modular Combination
+
+Large-capacity condensing units are commonly assembled from multiple factory modules manifolded together on a common refrigerant circuit. Where modules are combined, the manufacturer's certified combination shall be used and the manifold kit shall be the manufacturer's product. Total system capacity is [[drawing: as indicated on the mechanical schedules]].
+
+```datasheet
+label: Nominal System Cooling Capacity
+type: range
+unit: tons
+drawing_ref: true
+options:
+ min: 3
+ max: 60
+ setpoints: [3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20, 24, 30, 36, 42, 48, 54, 60]
+default: 12
+```
+
+## Connected Capacity Ratio
+
+The total nominal capacity of the indoor units connected to a circuit may exceed the condensing unit capacity up to the manufacturer's maximum connection ratio, taking advantage of load diversity (not all zones peak at once). The connection ratio shall be within the manufacturer's published limit. Over-connection beyond that limit prevents the system from meeting load when diversity is low; under-connection wastes condensing capacity.
+
+```datasheet
+label: Indoor-to-Outdoor Connection Ratio (max)
+type: range
+unit: %
+options:
+ min: 50
+ max: 200
+ setpoints: [50, 100, 130, 150, 200]
+default: 130
+```
+
+## Coil Corrosion Protection
+
+Air-source condensing unit coils in coastal or chemically aggressive environments shall have a factory-applied corrosion-protective coating. Within approximately 3 miles of a saltwater coast or in industrial atmospheres, an uncoated aluminum or copper coil corrodes within a few years, reducing capacity and shortening unit life.
+
+```datasheet
+label: Condenser Coil Corrosion Protection
+type: select
+options:
+ - "Standard coil (inland, non-corrosive environment)"
+ - "Factory-applied protective coating (coastal/industrial)"
+ - "Coastal-grade coil with enhanced coating (severe marine)"
+default: "Standard coil (inland, non-corrosive environment)"
+```
+
+## Sound
+
+Condensing unit sound power or sound pressure data shall be submitted, and the unit location and any required sound attenuation shall be coordinated with the project acoustic requirements and local noise ordinances. Rooftop and grade-mounted units near property lines or occupied spaces frequently drive complaints; a night-time low-sound operating mode should be specified where the unit is near noise-sensitive receptors.
+
+```datasheet
+label: Low-Sound Night Mode
+type: radio
+options:
+ - "Required — scheduled night-time sound reduction"
+ - "Not required"
+default: "Not required"
+```
+
+# Indoor Units
+
+## Indoor Unit Types
+
+Indoor fan-coil units are selected by zone type, ceiling and wall conditions, and architectural requirements. Each unit type recirculates room air across a refrigerant coil metered by an EEV and delivers no outdoor air. Ducted units serve concealed installations and multiple-diffuser zones and are the only types that accept an external static pressure; cassette, wall-mounted, and floor units are non-ducted and discharge directly into the space.
+
+```datasheet
+label: Indoor Unit Type
+type: select
+options:
+ - "Ducted — concealed, low static (concealed ceiling)"
+ - "Ducted — concealed, medium/high static"
+ - "Ceiling cassette — 4-way (2x2 or 3x3 grid)"
+ - "Ceiling cassette — 1-way or 2-way"
+ - "Wall-mounted (high wall)"
+ - "Floor-mounted / floor-standing console"
+ - "Ceiling-suspended (exposed)"
+default: "Ceiling cassette — 4-way (2x2 or 3x3 grid)"
+```
+
+The indoor unit schedule — tag, type, capacity, airflow, and connections for every unit — is [[drawing: as indicated on the indoor unit schedule and floor plans]].
+
+## Indoor Unit Capacity
+
+Indoor unit nominal capacity shall be selected to the zone load. Selecting an oversized indoor unit degrades dehumidification and comfort, because the unit's EEV throttles to a small opening and the coil runs warmer than intended; right-sizing each unit to its zone is required.
+
+```datasheet
+label: Indoor Unit Nominal Capacity
+type: range
+unit: MBH
+drawing_ref: true
+options:
+ min: 6
+ max: 96
+ setpoints: [6, 7.5, 9, 12, 15, 18, 24, 30, 36, 42, 48, 54, 72, 96]
+default: 12
+```
+
+## Ducted Unit External Static Pressure
+
+Ducted indoor units shall be selected for the external static pressure of the connected ductwork and air devices. Low-static concealed units serve short, simple duct runs; medium- and high-static units serve longer runs and higher-resistance distribution. Selecting a low-static unit on a duct system that exceeds its capability starves the zone of airflow.
+
+```datasheet
+label: Ducted Unit External Static Pressure
+type: range
+unit: in. w.g.
+drawing_ref: true
+options:
+ min: 0.1
+ max: 1.2
+ setpoints: [0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0, 1.2]
+default: 0.3
+```
+
+## Condensate Lift Pump
+
+Indoor units installed above the building drainage point — most cassette and concealed ceiling units — shall include an integral or accessory condensate lift pump and a float switch that shuts the unit down on high water level. The float interlock prevents condensate overflow and resulting ceiling damage when the pump or drain fails, and is required for all units that cannot drain by gravity.
+
+```datasheet
+label: Condensate Removal Method
+type: radio
+options:
+ - "Integral lift pump with high-level float shutdown"
+ - "Accessory lift pump with high-level float shutdown"
+ - "Gravity drain (unit above drainage point by gravity)"
+default: "Integral lift pump with high-level float shutdown"
+```
+
+## Indoor Unit Filtration
+
+Indoor units recirculate room air through an integral cleanable or replaceable filter intended to protect the coil, not to provide ventilation-grade filtration. Where enhanced filtration of the recirculated air is required, it shall be provided in a ducted unit's return or by a separate filtration device; the integral filter of a non-ducted unit shall not be relied on for occupied-space air cleaning.
+
+# Branch Controllers and Refrigerant Distribution
+
+## Refrigerant Distribution Devices
+
+Refrigerant flow from a condensing unit is divided to the indoor units through manufacturer distribution devices. Heat pump systems use refrigerant joints (Y-branches or headers) that simply split flow. Heat recovery systems additionally require branch controllers (refrigerant selector boxes) that direct hot discharge gas or cool liquid/suction to each indoor unit so that some units heat while others cool. The distribution topology shall match the certified system and is [[drawing: as indicated on the refrigerant one-line diagram]].
+
+```datasheet
+label: Refrigerant Distribution Device
+type: select
+options:
+ - "Branch joints / headers only (heat pump systems)"
+ - "Multi-port branch controller (heat recovery)"
+ - "Single-port branch controllers, one per indoor unit (heat recovery)"
+ - "Combination of multi-port and single-port branch controllers"
+default: "Multi-port branch controller (heat recovery)"
+```
+
+## Branch Controller Installation
+
+Branch controllers shall be installed in accessible locations — above an accessible ceiling, in a mechanical closet, or in a service space — with the manufacturer's required service clearance and a means of condensate drainage where the device can produce condensate. Branch controllers contain EEVs and electronics that require periodic service; locating them above inaccessible hard ceilings is not acceptable.
+
+# Refrigerant Safety and Leak Detection
+
+## Refrigerant Concentration Limit
+
+For every refrigerant circuit, the refrigerant concentration that would result from a single-fault release of the entire circuit charge into the smallest occupied space served by that circuit shall not exceed the refrigerant concentration limit (RCL) established by ASHRAE 15 and ASHRAE 34 for the refrigerant in use, unless mitigation is provided. This calculation, not merely the equipment selection, governs whether a VRF system is code-compliant in a given space. VRF circuits carry large refrigerant charges relative to the small zones their indoor units serve, so small rooms — private offices, hotel guest rooms, conference rooms — are the controlling spaces. The Contractor shall submit the concentration calculation for the smallest space on each circuit.
+
+```datasheet
+label: Refrigerant Concentration Compliance Basis
+type: radio
+options:
+ - "Charge limited so concentration in smallest space is below RCL without mitigation"
+ - "Mitigation provided where concentration could exceed RCL (detection + ventilation/airflow)"
+ - "Refrigerant-detection-system mitigation per ASHRAE 15 (A2L)"
+default: "Mitigation provided where concentration could exceed RCL (detection + ventilation/airflow)"
+```
+
+## A2L Leak Detection and Mitigation
+
+Where the system uses an A2L (mildly flammable) refrigerant such as R-32 or R-454B, a refrigerant detection system and mitigation shall be provided in accordance with ASHRAE 15 (or ASHRAE 15.2 for residential and light-commercial scope) and UL 60335-2-40 wherever the potential released concentration in an occupied space could exceed the applicable limit. The detection system shall, upon detecting refrigerant, initiate mitigation — typically energizing the indoor unit fan to disperse the refrigerant below its lower flammability limit (LFL), and where required, opening ventilation or activating an exhaust path. Detectors shall be located low in the space, because A2L refrigerants are heavier than air and accumulate near the floor. UL 60335-2-40 establishes a charge threshold below which detection and mitigation are not required; circuits with charges below that threshold for the served space may omit detection, but the calculation shall be submitted to demonstrate it.
+
+```datasheet
+label: A2L Refrigerant Detection System
+type: select
+options:
+ - "Factory-integrated detection and fan-dispersal mitigation in indoor units"
+ - "Field-installed A2L refrigerant detectors with fan/ventilation interlock"
+ - "Not required — charge below UL 60335-2-40 threshold for all served spaces (calculation submitted)"
+ - "Not applicable — non-flammable (A1) refrigerant"
+default: "Factory-integrated detection and fan-dispersal mitigation in indoor units"
+```
+
+## Machinery Room and Indoor Condensing Units
+
+Where condensing units are installed indoors (water-source systems) and the refrigerant quantity, classification, or arrangement triggers the machinery-room provisions of ASHRAE 15, the room shall meet the standard's requirements for refrigerant detection, mechanical ventilation, and access. The Engineer shall determine machinery-room applicability based on the refrigerant, the charge, and the room volume.
+
+```datasheet
+label: Indoor Equipment Room Classification
+type: radio
+options:
+ - "Not a refrigerating machinery room (charge/arrangement below ASHRAE 15 trigger)"
+ - "Refrigerating machinery room per ASHRAE 15 (detection and ventilation required)"
+ - "Not applicable — all condensing units outdoors"
+default: "Not applicable — all condensing units outdoors"
+```
+
+# Ventilation and DOAS Coordination
+
+## Outdoor Air Is Not Provided by the VRF System
+
+VRF indoor units recirculate room air only and introduce no outdoor air. The ventilation required by ASHRAE 62.1 and the mechanical code shall be provided by a separate dedicated outdoor air system (DOAS) — see [[sync/dedicated-outdoor-air-systems]] and [[sync/air-handling-units]]. A VRF system designed without a coordinated outdoor air source does not meet ventilation code and is one of the most common and serious VRF design errors. The DOAS shall condition outdoor air to a neutral or slightly dehumidified condition so the VRF units are not burdened with the full latent ventilation load.
+
+```datasheet
+label: Ventilation (Outdoor Air) Source
+type: select
+options:
+ - "Dedicated outdoor air system (DOAS) ducted to spaces"
+ - "DOAS ducted to indoor unit returns"
+ - "Energy recovery ventilator (ERV) — DOAS with energy recovery"
+ - "Outdoor air provided by separate system (see DOAS standard)"
+default: "Energy recovery ventilator (ERV) — DOAS with energy recovery"
+```
+
+## DOAS Delivery Strategy
+
+Outdoor air may be delivered directly to each space, or ducted into the return of the VRF indoor units. Direct-to-space delivery decouples ventilation from the VRF units and is the more robust approach; ducting outdoor air into indoor unit returns is acceptable only where the outdoor air is pre-conditioned to near-neutral, because raw outdoor air entering an indoor unit overwhelms its modest dehumidification capacity. The strategy and duct routing are [[drawing: as indicated on the mechanical plans]].
+
+# Controls
+
+## System Controller and Network
+
+The system shall be provided with the manufacturer's controller and refrigerant-network communication (transmission) wiring linking the condensing units, branch controllers, and indoor units. The transmission wiring topology and wire type shall follow the manufacturer's requirements; control wiring is distinct from line-voltage power wiring and shall be installed and separated per the manufacturer and NEC.
+
+```datasheet
+label: Zone Control Devices
+type: select
+options:
+ - "Wired wall-mounted controller per zone"
+ - "Wired controller shared across grouped zones"
+ - "Wireless/handheld controller per zone"
+ - "BAS-only control (no local zone controller)"
+default: "Wired wall-mounted controller per zone"
+```
+
+## BAS Integration
+
+The VRF system shall integrate with the building automation system per [[sync/building-automation-system]]. Integration shall be by a native communication interface or by a manufacturer gateway translating to the project's BAS protocol. The Contractor shall coordinate the protocol and the exchanged point list with the BAS contractor prior to submittal.
+
+```datasheet
+label: BAS Integration Protocol
+type: select
+options:
+ - "BACnet/IP via manufacturer gateway"
+ - "BACnet MS/TP via manufacturer gateway"
+ - "Modbus (RTU or TCP) via manufacturer gateway"
+ - "Native BACnet (no separate gateway)"
+ - "Hardwired contacts and analog points only"
+ - "Manufacturer proprietary front-end only (no BAS)"
+default: "BACnet/IP via manufacturer gateway"
+```
+
+## Minimum Control and Monitoring Points
+
+At minimum, the controls interface shall provide, per zone or per system as applicable: zone temperature setpoint and space temperature; mode (cool/heat/auto/fan/off) command and status; fan speed command and status; occupancy or schedule control; indoor unit run status and fault/alarm; condensing unit run status, fault/alarm, and operating mode; refrigerant leak detection alarm; and condensate high-level alarm.
+
+```datasheet
+label: Control and Monitoring Points
+type: checkbox
+options:
+ - "Zone temperature and setpoint"
+ - "Mode command and status (cool/heat/auto/fan/off)"
+ - "Fan speed command and status"
+ - "Occupancy / schedule control"
+ - "Indoor unit run status and fault/alarm"
+ - "Condensing unit status, fault/alarm, and mode"
+ - "Refrigerant leak detection alarm"
+ - "Condensate high-level alarm"
+ - "Energy / power monitoring per system"
+default: "Zone temperature and setpoint"
+```
+
+# Refrigerant Piping
+
+Refrigerant piping connecting condensing units, branch controllers, and indoor units shall be designed, sized, fabricated, and installed in accordance with [[sync/refrigerant-piping]], ASHRAE 15, and the equipment manufacturer's published design limits and software. This standard governs the equipment and system; the piping construction standard governs the piping. The following equipment-driven constraints shall nonetheless be confirmed during design and recorded in the piping design report.
+
+## Piping Length and Elevation Limits
+
+Total piping length, the length to the farthest indoor unit, the length beyond the first branch, and the elevation differences between the condensing unit and indoor units and between indoor units shall all be within the manufacturer's published maximums for the selected system. Exceeding these limits degrades capacity, impairs oil return, and voids the warranty. The manufacturer's piping design software output confirming compliance shall be submitted.
+
+## Oil Return
+
+The piping design and operating controls shall ensure positive oil return to the compressors under all operating conditions, including extended low-load operation and long vertical risers. Where the manufacturer requires oil traps, double risers, or periodic oil-recovery operating cycles for the as-designed layout, they shall be provided. Loss of oil return is a leading cause of VRF compressor failure on long or tall piping runs.
+
+## Additional Refrigerant Charge
+
+The field-added refrigerant charge shall be calculated from the installed liquid-line lengths and diameters per the manufacturer's method, weighed in during charging, and recorded. The total installed charge per circuit shall be used in the final refrigerant concentration (RCL) calculation and recorded in the refrigerant tracking documentation.
+
+# Installation
+
+## Equipment Setting and Support
+
+Condensing units shall be set level on housekeeping pads, roof curbs, or rails sized and anchored for the unit operating weight and the applicable wind and seismic loads, with the manufacturer's required service and airflow clearances maintained on all sides. Indoor units shall be supported independently of ductwork and piping and installed level so that condensate drains correctly. Unit locations and arrangement are [[drawing: as indicated on the mechanical plans]].
+
+## Vibration Isolation
+
+Condensing units shall be mounted on vibration isolators or isolation rails appropriate to the unit and the structure, and all piping, conduit, and condensate connections to isolated units shall be made with flexible connections so the isolation is not short-circuited.
+
+## Seismic Restraint
+
+Where required by the applicable building code (IBC/ASCE 7) for the seismic design category, condensing units, indoor units, and branch controllers shall be seismically restrained per submitted calculations and details.
+
+## Condensate Piping
+
+Condensate drain piping shall be run from every indoor unit and branch controller that produces condensate to an approved disposal point, sized for the design condensate rate, sloped for gravity flow downstream of any lift pump, insulated to prevent sweating in occupied and concealed spaces, and provided with a cleanout or accessible connection for service.
+
+## Electrical Coordination
+
+Power wiring shall be sized to the MCA and protected at the MOCP scheduled for each unit, per NFPA 70. Control (transmission) wiring shall be the manufacturer's specified type, installed separately from line-voltage power and per the manufacturer's network topology rules. The Contractor shall coordinate disconnect locations and convenience receptacles required for service at each condensing unit.
+
+# Startup and Commissioning
+
+## Evacuation and Leak Testing
+
+Before charging, the refrigerant piping system shall be pressure-tested for leaks and evacuated (triple evacuation to the manufacturer's target vacuum is the typical method) to remove moisture and non-condensables. Pressure-test pressure, hold duration, and final vacuum shall be recorded. A system charged without proper evacuation will suffer moisture-induced acid formation and premature compressor failure.
+
+## Charging
+
+The factory charge plus the calculated field-added charge shall be weighed in, not gauged by pressure, and the total recorded per circuit. The installed charge shall be reconciled against the refrigerant concentration calculation for the smallest served space.
+
+## Factory-Authorized Startup
+
+Initial startup and commissioning shall be performed by a manufacturer-authorized field technician, who shall verify communication addressing of every indoor unit, branch controller, and condensing unit; confirm correct zone-to-unit assignments against the indoor unit schedule; run the manufacturer's automated commissioning/test-run routine; and verify cooling and heating operation, mode change, and (for heat recovery) simultaneous cooling and heating. The signed startup report is a condition of the warranty.
+
+```datasheet
+label: Startup and Commissioning Scope
+type: checkbox
+options:
+ - "Pressure test and recorded leak test"
+ - "Evacuation to manufacturer vacuum target (recorded)"
+ - "Weighed-in charge recorded per circuit"
+ - "Manufacturer automated commissioning / test run"
+ - "Address and zone assignment verification against schedule"
+ - "Cooling, heating, and mode-change verification"
+ - "Heat recovery simultaneous cool/heat verification"
+ - "Refrigerant leak detection and mitigation interlock test"
+ - "BAS point-to-point verification"
+ - "DOAS interlock and ventilation verification"
+default: "Manufacturer automated commissioning / test run"
+```
+
+## Functional Performance and Balancing
+
+After startup, the system shall be verified to deliver the scheduled conditions in each zone, and ducted indoor unit airflows shall be balanced per [[sync/testing-adjusting-and-balancing]]. Controls sequences, including leak-detection mitigation, condensate alarms, and DOAS interlocks, shall be functionally tested and documented.
+
+# Warranty
+
+The manufacturer shall warrant the complete VRF system, including compressors, against defects in materials and workmanship for the manufacturer's standard period, which for VRF equipment commissioned by a factory-authorized technician is commonly ten years on the compressor and a shorter period on parts. The warranty period, coverage, and any registration or authorized-startup conditions shall be documented in the closeout submittal. The Contractor shall complete all registration and submit the signed factory startup report required to activate the full warranty term.
+
+```datasheet
+label: Warranty Period (Compressor)
+type: select
+unit: years
+options:
+ - "5 years"
+ - "7 years"
+ - "10 years (factory-authorized startup required)"
+ - "12 years (extended, where offered)"
+default: "10 years (factory-authorized startup required)"
+```
+
+```datasheet
+label: Warranty Period (Parts)
+type: select
+unit: years
+options:
+ - "1 year"
+ - "5 years"
+ - "7 years"
+ - "10 years"
+default: "7 years"
+```