Variable Refrigerant Flow (VRF) Systems
Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
Showing changes from Rev 5
to Rev 6
in Variable Refrigerant Flow (VRF) Systems.
---
title: Variable Refrigerant Flow (VRF) Systems
…114 unchanged lines
- "Refrigerant tracking documentation per circuit"
- "Warranty documentation"
−default: [Operation and maintenance manuals, Signed commissioning and startup report (charge, evacuation, leak test), As-built system schematic, Final refrigerant concentration (RCL) calculation, Controls point list, network address map, and final sequence of operation, Refrigerant tracking documentation per circuit, Warranty documentation]
+default:
+ - "Operation and maintenance manuals"
+ - "Signed commissioning and startup report (charge, evacuation, leak test)"
+ - "As-built system schematic"
+ - "Final refrigerant concentration (RCL) calculation"
+ - "Controls point list, network address map, and final sequence of operation"
+ - "Refrigerant tracking documentation per circuit"
+ - "Warranty documentation"
```
…52 unchanged lines
### 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. {note}
+### 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.
+
```datasheet
label: Condensing Unit Installation Environment
…7 unchanged lines
```
+### 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: Design Winter Heating Ambient (lowest)
…8 unchanged lines
```
−### 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.
−
−### Where the design winter ambient is below the standard equipment rating, a low-temperature heating model or a supplemental heat source shall be provided.
−
## Low-Ambient Heating Capability {toc}
…25 unchanged lines
### 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. {note}
+### The VRF system type shall be specified as heat pump or heat recovery based on whether simultaneous heating and cooling is required across zones.
+
```datasheet
label: VRF System Type
…12 unchanged lines
### 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. {note}
+### The condenser heat rejection source shall be specified based on outdoor access, building height, and availability of a condenser-water or geothermal loop.
+
```datasheet
label: Condenser Heat Rejection Source
…14 unchanged lines
### 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. {note}
+### 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
…6 unchanged lines
```
−### The specifier shall confirm the refrigerant offered for the selected equipment generation, because the leak detection, mitigation, and concentration requirements depend on it.
−
# Outdoor and Condensing Units {toc}
…2 unchanged lines
### Continuous inverter modulation is the basis of VRF part-load efficiency and is required. {note}
+### Condensing units shall employ inverter-driven (variable-speed) compressors that modulate capacity continuously to match the connected load.
+
```datasheet
label: Compressor Modulation
…5 unchanged lines
```
−### 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.
…3 unchanged lines
### Large-capacity condensing units are commonly assembled from multiple factory modules manifolded together on a common refrigerant circuit. {note}
−### Total system capacity is [[drawing: as indicated on the mechanical schedules]]. {note}
+### Total system capacity is [[drawing: as indicated on the mechanical schedules]].
```datasheet
…50 unchanged lines
### Rooftop and grade-mounted units near property lines or occupied spaces frequently drive complaints. {note}
+### 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.
+
+### A night-time low-sound operating mode should be specified where the unit is near noise-sensitive receptors.
+
```datasheet
label: Low-Sound Night Mode
…5 unchanged lines
```
−### 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.
−
−### A night-time low-sound operating mode should be specified where the unit is near noise-sensitive receptors.
−
# Indoor Units {toc}
…3 unchanged lines
### Each unit type recirculates room air across a refrigerant coil metered by an EEV and delivers no outdoor air. {note}
### 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. {note}
−### 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]]. {note}
+### 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]].
```datasheet
…51 unchanged lines
### The float interlock prevents condensate overflow and resulting ceiling damage when the pump or drain fails. {note}
+### 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.
+
```datasheet
label: Condensate Removal Method
…6 unchanged lines
```
−### 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.
−
### A float interlock is required for all units that cannot drain by gravity.
…14 unchanged lines
### 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. {note}
+### The distribution topology shall match the certified system and is [[drawing: as indicated on the refrigerant one-line diagram]].
+
```datasheet
label: Refrigerant Distribution Device
…7 unchanged lines
```
−### The distribution topology shall match the certified system and is [[drawing: as indicated on the refrigerant one-line diagram]].
−
## Branch Controller Installation {toc}
…10 unchanged lines
### 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. {note}
+### 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.
+
```datasheet
label: Refrigerant Concentration Compliance Basis
…6 unchanged lines
```
−### 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.
−
### The Contractor shall submit the concentration calculation for the smallest space on each circuit.
…4 unchanged lines
### UL 60335-2-40 establishes a charge threshold below which detection and mitigation are not required. {note}
+### 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.
+
```datasheet
label: A2L Refrigerant Detection System
…7 unchanged lines
```
−### 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.
…24 unchanged lines
### VRF indoor units recirculate room air only and introduce no outdoor air. {note}
+### 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]].
+
```datasheet
label: Ventilation (Outdoor Air) Source
…7 unchanged lines
```
−### 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]].
−
### 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.
…203 unchanged lines
## The Contractor shall complete all registration and submit the signed factory startup report required to activate the full warranty term.