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 rraustad@fsec.ucf.edu

Full-Load Cooling Performance Controlled Region Uncontrolled Region

Full-Load Heating Performance

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

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)

Creating Performance Curves Raustad, R.A., 2012. Creating Performance Curves for Variable Refrigerant Flow Heat Pumps in EnergyPlus, FSEC-CR-1910-12. https://securedb.fsec.ucf.edu/pub/pub_search https://securedb.fsec.ucf.edu/pub/pub_show_detail?v_pub_id=4588 [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]

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]

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

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

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

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

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

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]

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

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

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

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