VRF/VRV System Guide
Variable Refrigerant Flow (VRF) systems offer precise temperature control, energy efficiency, and design flexibility for commercial and residential applications.
What is VRF/VRV?
Variable Refrigerant Flow (VRF) is an advanced HVAC technology that uses refrigerant as the cooling and heating medium. Unlike traditional systems that deliver conditioned air through ducts, VRF systems transport refrigerant directly to indoor units.
VRV (Variable Refrigerant Volume) is Daikin's trademarked name for VRF technology. Daikin invented VRV in 1982 in Japan, and the terms VRF and VRV are often used interchangeably.
Key Features
- Inverter-driven variable speed compressor
- Multiple indoor units from one outdoor unit
- Individual zone temperature control
- Heat recovery capability (simultaneous heating/cooling)
- Up to 64 indoor units per system
System Capacity Range
* Connection ratio allows oversizing indoor units relative to outdoor unit capacity for diversity factor.
How VRF Systems Work
Cooling Mode
- 1 Compressor pressurizes refrigerant to high-pressure gas
- 2 Hot gas flows to outdoor condenser coil
- 3 Condenser rejects heat to outdoor air, gas becomes liquid
- 4 High-pressure liquid travels to indoor EEV
- 5 EEV meters refrigerant, drops pressure and temperature
- 6 Cold refrigerant absorbs heat from room air
- 7 Low-pressure gas returns to compressor
Heating Mode (Heat Pump)
- 1 Reversing valve redirects refrigerant flow
- 2 Hot discharge gas flows to indoor units first
- 3 Indoor coil releases heat to room air
- 4 Refrigerant condenses to liquid
- 5 Liquid flows to outdoor unit EEV
- 6 Outdoor coil absorbs heat from outdoor air
- 7 Cold gas returns to compressor
Inverter-Driven Variable Speed
Variable Speed Compressor
Modulates from 10% to 100% capacity to match exact load requirements
Energy Savings
30-50% more efficient than conventional systems at part-load conditions
Precise Control
Maintains temperature within ±0.5°F of setpoint
VRF System Types
2-Pipe Heat Pump System
Cooling OR Heating (not simultaneous)
How It Works
All indoor units operate in the same mode. The outdoor unit switches between cooling and heating based on majority demand.
Piping Configuration
Best For
- • Single-zone or same-zone buildings
- • Residential applications
- • Lower initial cost requirement
- • Buildings with uniform load patterns
Pros
Lower installation cost, simpler piping
Cons
No simultaneous heating and cooling
3-Pipe Heat Recovery System
Simultaneous Heating AND Cooling
How It Works
Uses branch selector (BS) boxes to direct hot or cold refrigerant to individual zones. Heat rejected from cooling zones is recycled to heating zones.
Piping Configuration
Best For
- • Multi-zone commercial buildings
- • Buildings with diverse load profiles
- • Perimeter vs interior zone conflicts
- • Maximum energy efficiency requirements
Pros
Energy recycling, individual zone control, highest efficiency
Cons
Higher initial cost, more complex piping
Heat Recovery Efficiency
Example Scenario
In a typical office building, north-facing rooms may need heating while south-facing rooms with sun exposure need cooling. With heat recovery:
- Heat rejected from cooling zones is captured
- Recycled to zones needing heating
- Reduces compressor work and energy consumption
Energy Savings Potential
COP = Coefficient of Performance (heating output / energy input)
VRF System Components
Outdoor Unit (ODU)
- Compressor: Inverter scroll or rotary (DC motor)
- Heat Exchanger: Condenser/evaporator coil
- Fans: Variable speed DC fans
- Controls: Main PCB, inverter board
- Accessories: Oil separator, accumulator, filter drier
Indoor Units (IDU)
- Wall Mount: Residential, small offices
- Ceiling Cassette: 4-way, 2-way, 1-way
- Concealed Duct: Hidden installation
- Floor Standing: Visible or concealed
- Ceiling Suspended: Open ceiling applications
Distribution Components
- Refnet Joints: Y-branch piping connections
- Branch Selector (BS): Heat recovery mode switch
- EEV: Electronic Expansion Valve (each IDU)
- Subcooling Coil: Heat recovery efficiency
- Oil Return: Oil management system
Indoor Unit Types
Wall Mount
0.5-2.5 tons
4-Way Cassette
1-5 tons
Concealed Duct
0.5-8 tons
Floor Standing
1-3 tons
Ceiling Suspend
1-4 tons
VRF vs Traditional HVAC Systems
| Feature | VRF System | RTU/Split System | Chilled Water |
|---|---|---|---|
| Building Size | 10,000-500,000 sq ft | Up to 50,000 sq ft | 100,000+ sq ft |
| Zone Control | Excellent (per room) | Limited | Good (with VAV) |
| Energy Efficiency | Highest (part load) | Moderate | High (large scale) |
| Installation Space | Minimal (no ductwork) | Large ducts required | Chiller room + piping |
| Initial Cost | $15-25/sq ft | $8-15/sq ft | $20-40/sq ft |
| Heat Recovery | Yes (3-pipe) | No | With 4-pipe system |
| Noise Level | Very quiet | Moderate | Varies |
| Refrigerant Charge | High (distributed) | Low | Contained |
| Maintenance | Specialized required | Standard HVAC | Specialized required |
VRF Advantages
- • Superior energy efficiency at part load
- • Individual zone temperature control
- • Quiet operation
- • Flexible installation (no large ducts)
- • Heat recovery capability
- • Long piping runs possible
- • Easy expansion/modification
- • Quick installation time
VRF Considerations
- • Higher initial equipment cost
- • Specialized technician training required
- • Large refrigerant charge (leak concerns)
- • Proprietary parts and controls
- • No fresh air delivery (need DOAS)
- • Refrigerant management complexity
- • Code restrictions in some jurisdictions
- • Limited domestic hot water capability
Major VRF Manufacturers
Daikin VRV
Japan (Inventor of VRV - 1982)
- VRV IV: Standard heat pump/heat recovery
- VRV IV+: Enhanced efficiency
- VRV IV W+: Water-cooled
- VRV A: North America residential
Mitsubishi CITY MULTI
Japan
- Y Series: Heat pump
- R2 Series: Heat recovery
- S Series: Compact
- W Series: Water-source
LG Multi V
South Korea
- Multi V 5: Standard series
- Multi V S: Single-phase compact
- Multi V Water: Water-cooled/source
- Multi V i: Inverter scroll
Samsung DVM
South Korea
- DVM S: Standard series
- DVM S2: High efficiency
- DVM Chiller: Hybrid system
- DVM ECO: Inverter 1-phase
Toshiba SMMS
Japan (via Carrier)
- SMMS-i: Standard VRF
- SMMS-u: Universal outdoor
- SMMSe: Entry level
- MiNi-SMMS: Small applications
Fujitsu Airstage
Japan
- J-IIS: Standard heat pump
- V-IIS: Heat recovery
- J-IIIL: Low ambient
- Mini VRF: Small commercial
Refrigerants in VRF Systems
R-410A
Current Standard
Most common current VRF refrigerant. Being phased down due to high GWP.
R-32
Lower GWP Alternative
Gaining popularity globally. A2L mild flammability classification.
R-454B
Future Standard (US)
Designed as R-410A replacement. A2L classification.
Note: VRF systems have larger refrigerant charges distributed throughout the building. New codes (ASHRAE 15, IMC 2024) require refrigerant detection and ventilation systems for A2L refrigerants in occupied spaces.
Ideal VRF Applications
Office Buildings
Individual zone control for tenant spaces
Hotels
Room-by-room temperature control
Healthcare
Precise temperature/humidity control
Schools
Classroom-level control, quiet operation
Retail
Multi-tenant, flexible fit-out
High-End Residential
Whole-home zoning, no ducts
Historic Buildings
Minimal invasive installation
Retrofits
No existing ductwork required