HVAC Test results Anish Gaikwad Parag Mitra WECC LMTF Meeting Salt Lake City, UT 3 Oct 2017

Disclaimer and test information The test is intended to add more data points to the present set of observations to refine our current estimates of parameters of the Motor D model We have tested only two units and thus test results are not necessary universal 2 units tested so far- 2 Ton Trane unit, single speed (No VFD) with Trane Climatuff scroll compressor 4 Ton Armstrong unit, single speed (No VFD) with Copeland scroll compressor

Test setup Supply V/I Run/Start winding V and I Programmable Power supply Lab ambient temperature Temp controlled chamber Outdoor unit/ Compressor Supply V/I Run/Start winding V and I Indoor/Outdoor fan V and I Outdoor/ Indoor Temperature Comp. Inlet/Outlet pressure Indoor unit Monitoring system

Test waveforms Rectangular sags Ramped recovery sags POW 0, 90 degrees Ramp 0.5 cycle (dip/recovery) Sag levels 0.4, 0.45, 0.5 (pu) Duration 2, 3, 4, 5, 6, 9, 12 cycles Recovery 0.85 pu then 1 pu Ramped recovery sags POW Ramp 0.5 cycle (dip) Sag levels 0.4, 0.45, 0.5, 0.6, 0.7(pu) Duration 3 cycles Recovery 1 pu with 30 s ramp Temperature : 85 F, 95 F, 105 F, 115 F Relative Humidity: 36%

HVAC Stall determination Note that it is not possible to measure the motor speed For rectangular sags For 0.85 pu real power is almost 3.5 times the base KW kW consumption should be greater than 3.5 times the times the base KW at that outdoor temperature Duration of the 3.5 times base KW period should be greater than the inrush current durations Inlet Outlet For ramped recovery sags Power does not jump as voltage recovers slowly if the motor restarts The inlet and outlet pressure can be seen to equalize as the motor is stalled and not compressing any more It is critical to define “stall mode” in the context of scroll compressors

Unit Description (Trane 2-Ton) Manufacturer Trane, Trane Climatuff (No VFD, single speed) Size 2 Ton Voltage rating 240V/ 60 Hz Rated, Locked rotor amps 8.3, 58 amps Refrigerant R-410 Motor type Cap. Start, Cap. Run Cap. size Start: 196 μF, Run 35 μF 35 μF 196 μF Temp Steady state amps 85 6.2 95 6.7 105 7.6 115 8.3

Cold start up of the unit (2-Ton Trane, Climatuff compressor) Multiple cold restarts were performed: Unit started between 5 – 6 cycles or 0.083s approximately Input voltage (Volts) 5X scaled input current (Amps)

2-Ton Unit: Summary of results (rectangular sags) UV contactor tripped when voltage dropped below 0.45 – 0.4 pu. Contactor dropout was independent of outdoor temperature The A/C stalled only if the contactor dropped out and reconnected back The A/C invariably stalls for voltage below the 0.45-0.4 pu range. Vstall can be assumed to be in the range 0.45-0.4 pu. For the Vstall, the A/C invariably stalls for a sag of 2-3 cycles. Tstall can be assumed to be 2-3 cycles. The values of Vstall and Tstall as indicated were consistent across all temperatures (85°, 95°, 105°, 115° F) The unit started up for the rectangular sags at all temperatures and TOL did not operate Reverse rotation of the compressor was not observed for this unit

2-Ton Unit: Summary of results (30 sec. ramped recovery) NOTE: These test were performed to gain deeper insights Not meant to replicate an actual sag For the ramped recovery tests, thermal overload operated only for 115° F for sag levels of 0.4, 0.45, 0.5 pu. Unit takes longer time to restart at 115 F and therefore trips on thermal overload The thermal overload operated 7-8s after the A/C stalled Thermal overload operation is a function of both current and time for which the large current persists When the A/C motor slows down, the start capacitor connects. The starting cap is large (196 μF) and causes the net current to be capacitive for a short period. Capacitor helps in terms of providing the reactive power demand In Motor D model, the Motor D draws large inductive current when stalled

Example: Stalling of A/C due to opening of contactor Temp 105 F POW 90 Vsag 0.4 pu Duration 2 cycles Vrecovery 0.85 for 1s then to 1 pu Both sag and recovery have a 0.5 cycle ramp

Example: A/C motor deceleration and acceleration without stalling Temp 105 F POW 90 Vsag 0.5 pu Duration 4 cycles Vrecovery 0.85 for 1s then to 1 pu Both sag and recovery have a 0.5 cycle ramp Motor D won’t capture this spike if Vstall is set to 0.45pu

Example: Thermal overload operation on ramped voltage recovery Temp 115 F POW 90 Vsag 0.4 pu Duration 3 cycles Vrecovery 30 s ramp to 1 pu Input contactor remains connected so the voltages do not go to zero Input, run and start winding currents go to zero as the thermal overload operates Pressure difference between discharge and suction valves starts to equalize Thermal overload was observed to operate in 8-8.2 s approx.

Example: Thermal overload operation comparison at different temperature Vsag 0.4 pu Duration 3 cycles Vrecovery 30 s ramp to 1 pu 95 F 115 F 8s approx. 6.5s approx. A/C takes longer time to restart at a higher ambient temperature and trips due to thermal overload

Unit Description: 4 Ton Armstrong, Copeland Scroll Manufacturer Armstrong, Copeland (No VFD, single speed) Size 4 Ton Voltage rating 240V/ 60 Hz Rated, Locked rotor amps 16.5 , 117 amps (24.3 amps for contactor sizing) Refrigerant R-410 Motor type Permanent Split Cap Cap. size 70 μF (comp) + 10μF (Fan) Temp Steady state amps 85 12.42 95 13.73 105 15.17 115 16.81 Start Run 70 mfd PSC

Cold start up of the unit (4 Ton Armstrong, Copeland compressor) Multiple cold restarts were performed: Unit started between 11-12 cycles or 0.2s approximately Input voltage (Volts) 5X scaled input current (Amps)

4 Ton Unit: Summary of results (rectangular sags) UV contactor tripped when voltage dropped below 0.55 – 0.5 pu (Note this is higher than the 2 ton unit) Contactor dropout was independent of outdoor temperature Once the contactor opens, the A/C won’t re-connect before 5 minutes (similar to trip due to thermal overload) This is a standard recommended manufacturer set delay for protection against short cycling and reverse rotation. Confirmed by both HVAC contractor and compressor manufacturer. This behavior cannot be captured by the present Motor D model For a simulation study this means that once the contactor trips, the load is lost. Better in terms of voltage recovery, but loss of load may mean possible overvoltage For the rectangular sag, stalling of the A/C unit was not observed. The contactor tripped the unit before it stalled.

Example: A/C motor deceleration and acceleration without stalling Temp 105 F POW 90 Vsag 0.6 pu Duration 12 cycles Vrecovery 0.85 for 1s then to 1 pu Both sag and recovery have a 0.5 cycle ramp

Example: A/C motor contactor opening Temp 105 F POW 90 Vsag 0.55 pu Duration 3 cycles Vrecovery 0.85 for 1s then to 1 pu Both sag and recovery have a 0.5 cycle ramp

2 Ton vs. 4 Ton comparison Description 2 Ton 4 Ton Rated amps, Locked rotor amps 8.3, 58 16.15, 117 Type of motor Cap start, Cap run Current at low motor speeds can be capacitive at times Permanent split cap Current at low motor speed is inductive Contactor drop out voltage 0.45-0.4 pu Reconnects on voltage recovery 0.55-0.5 pu Does not reconnect before 5 mins Stalling Stalls when contactor trips Vstall 0.45- 0.4, Tstall 2-3 cycles No stalling Trips due to contactor and doesn’t reconnect before 5 mins Thermal overload Operates for ramped recovery during higher ambient temperatures No thermal overload operation observed

Conclusions The 2 Ton unit test results indicates Vstall=0.45 and Tstall=0.032 (as suggested now) is within the realm of possibility For both units, the temperature did not have any effect on the stalling for the rectangular sags The 4 Ton unit never stalled for any rectangular sag The contactor trip behavior of the 4 Ton unit cannot be captured by using the standard motor D parameters Results indicate: Drop out voltage: 0.55-0.5 pu, Reconnection voltage: 999 (high value) Differences where observed in the operation of the TOL for the ramped recovery sags, with temperature (only for the 2 Ton unit) TOL was found to operate at higher temperature