1. Variable Capacity Heat Pump RTF Sub-Committee
February 27, 2013
VRF Fan Energy Use and Part-Load Performance
Richard Raustad, Senior Research Engineer
Florida Solar Energy Center

2. Full-Load Cooling Performance
Controlled Region
Uncontrolled Region

3. Full-Load Heating Performance

4. Manufacturer Performance Correction (surrogate for part-load performance)
170
136
Capacity (kBtu/hr)
102 68 34
21 kW
28.1 kW
72 kBTU/hr
96 kBTU/hr

5. EnergyPlus Cooling Model Inputs
AirConditioner:VariableRefrigerantFlow,
autosize, !- Rated Total Cooling Capacity {W}
3.802, !- Rated Cooling COP {W/W}
-5, !- Minimum Outdoor Temperature in Cooling Mode {C}
43, !- Maximum Outdoor Temperature in Cooling Mode {C}
VRFCoolCapFT, !- Cooling Capacity Ratio Modifier Function of Low Temperature Curve Name
VRFCoolCapFTBoundary, !- Cooling Capacity Ratio Boundary Curve Name
VRFCoolCapFTHi, !- Cooling Capacity Ratio Modifier Function of High Temperature Curve Name
VRFCoolEIRFT, !- Cooling Energy Input Ratio Modifier Function of Low Temperature Curve Name
VRFCoolEIRFTBoundary, !- Cooling Energy Input Ratio Boundary Curve Name
VRFCoolEIRFTHi, !- Cooling Energy Input Ratio Modifier Function of High Temperature Curve Name
CoolingEIRLowPLR, !- Cooling Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name
CoolingEIRHiPLR, !- Cooling Energy Input Ratio Modifier Function of High Part-Load Ratio Curve Name
CoolingCombRatio, !- Cooling Combination Ratio Correction Factor Curve Name
VRFCPLFFPLR, !- Cooling Part-Load Fraction Correlation Curve Name (cycling losses)

6. Creating Performance Curves
Raustad, R.A., Creating Performance Curves for Variable Refrigerant Flow Heat Pumps in EnergyPlus, FSEC-CR
[59 F]
[60.8 F]
[64.4 F]
[68 F]
[71.6 F]
[75.2 F]
[41 F]
[50 F]
[86 F]
[95 F]
[78.8 F]
[-4]
[F]
[131]

7. Laboratory Measured Data
Full-load Cooling Performance
[29.4/21.1]
[29.4/19.4]
[29.4/17.2]
[26.7/21.1]
[26.7/19.4]
[26.7/17.2]
[26.7/15.6]
[23.8/21.1]
[23.9/19.4]
[23.8/17.2]
AHRI 1230
Buried TSTAT setting
[23.9]
[20.6]
[17.8]
[15.0] WB
[-17.7]
[10]
[37.8]
[65.6]
[C]

8. Measured part-load operation
[15.3 kW]
Outdoor Temperature (F) [C]
[23.9 C]
[29.4 C]
[35 C]
[40.5 C]
Normalized Capacity
[26.7 C/ 19.4 C]
[15.3 kW]
170
136
102
Capacity (kBtu/hr) 68 34

9. Model Characteristics
170
136
Capacity (kBtu/hr)
102 68 34
[kW]
[58.6]

10. Major Difference between VRF HP’s and Conventional HP’s
Avoid duct losses when using ductless terminal units (no heat gain or leakage)

11. Major Difference between VRF HP’s and Conventional HP’s
Avoid duct losses when using ductless terminal units (no heat gain or leakage)

12. Major Difference between VRF HP’s and Conventional HP’s
Avoid duct losses when using ductless terminal units (no heat gain or leakage)
Fan energy savings for ductless terminal units

13. Major Difference between VRF HP’s and Conventional HP’s
Avoid duct losses when using ductless terminal units (no heat gain or leakage)
Fan energy savings for ductless terminal units
Moderate part-load
savings
170
136
Capacity (kBtu/hr)
102 68 34
[kW]
[58.6]

14. Major Difference between VRF HP’s and Conventional HP’s
Avoid duct losses when using ductless terminal units (no heat gain or leakage)
Fan energy savings for ductless terminal units
Moderate part-load savings
Space savings for refrigerant lines vs air ducts

15. Major Difference between VRF HP’s and Conventional HP’s
Avoid duct losses when using ductless terminal units (no heat gain or leakage)
Fan energy savings for ductless terminal units
Moderate part-load savings
Space savings for refrigerant lines vs air ducts
Individual zone control

16. Future work
Need more laboratory research and published experimental data
Better understanding of control logic
Field demonstrations need more information
Work closely with manufacturer’s

17. Richard Raustad rraustad@fsec.ucf.edu
Questions?
Richard Raustad