ultima ultra multi-temp ultra xl extra optima with standard micro prior ...

1.17 REFRIGERANT CIRCUIT DURINGHEATING AND DEFROSTING(See Figures 1-23, 1-24 or 1-25)For units with UltraFreeze refer to section 1.13.For units without UltraFreeze the unit will only heat whenthe controller is set above +10_F ( --- 12.2_C) as the heatrelays are electronically locked out with set points below+10_F ( --- 12.2_C).When vapor refrigerant is compressed to a high pressureand temperature in a reciprocating compressor, themechanical energy necessary to operate the compressor istransferredtothegasasitisbeingcompressed.Thisenergyis referred to as the “heat of compression” and is used as thesource of heat during the heating cycle.The quench valve (R-22 Only) opens as required tomaintain a 265 to 285_F (129 to 141_C) maximumdischarge temperature.1.17.1Heating and DefrostNOTES1.Solenoid valve (SV-2) remains open duringheating or defrosting to allow additionalrefrigerant to be metered into the hot gas cycle(through the expansion valve) providingadditional heating capacity until de-energizedby head pressure control switch HP-2.2. SV-3 on Ultima’s, will not open when theambient temperature exceeds 80_F (26.7_C).3.SV-3 will open after a 60 second delay, if theengine is in high speed and the differencebetween ambient and discharge temperaturesexceeds 100_F (55.5_C). If the differencebetween ambient and discharge temperaturesgoes below 50_F (27.8_C) SV-3 will close.When the controller calls for heating, hot gas solenoidvalve (SV-4) opens and the condenser pressure controlsolenoid valve (SV-1) closes. The condenser coil then fillswith refrigerant, and hot gas from the compressor entersthe evaporator. Also the liquid line solenoid valve (SV-2)will remain energized (valve open) as the head pressurecontrol switch (HP-2) will remain closed until thecompressor discharge pressure increases to cut-outsetting (refer to section 1.4).9Switch HP-2 opens to de-energize the liquid line solenoidvalve (SV-2) and the valve closes to stop the flow ofrefrigerant to the expansion valve.When the compressor discharge pressure falls to cut-insetting (refer to section 1.4), pressure switch (HP-2) closesand in turn energizes the normally closed liquid solenoidvalve (SV-2) which opens, allowing refrigerant from thereceiver to enter the evaporator through the expansionvalve.When in engine operation and the discharge pressureexceeds pressure settings detailed in section 1.4, pressurecutout switch (HP-1) opens to de-energize the run relaycoil (RR). When the RR coil is de-energized, the RRcontacts open stopping the engine. The function of thehot gas bypass line is to raise the receiver pressure whenthe ambient temperature is low (below 0_F = ---17.8_C)so that refrigerant flows from the receiver to theevaporator when needed.1.17.2Defrost with Greater Than 100_F (37.8_C)Ambienta. Diesel Engine OperationUnits utilizing the new wiring harness & HR4 relay willinitiate a pump down cycle during defrost above 100_Fambient temperature.(See Figure 1-11)Units with older wiring harness, will not have HR4 and nopump down cycle.If the ambient is greater than 100_F (37.8_C) thefollowing stages are performed for defrost (Refer toTable 1-9). The first stage (Pump Down) runs for aminimum of thirty seconds and then checks the suctionpressure. When the suction pressure is less than 10 PSIG,it will continue to stage 2. The total time in stage onecannot be greater than 330 seconds. If 330 seconds isreached stage two (Defrost Begins) will automatically beentered regardless of suction pressure. Stage 2 is defrost.Stage 3 (Defrost Termination) is the termination ofdefrost. When defrost is terminated SV4 will remainenergized for 15 seconds.b. Electric Standby Motor OperationOn electric standby motor operation HR4 relay is used toinitiate a pump down cycle in heat or defrost.Table 1-9. Stages for Defrost with Greater Than 100 _F (37.8_C) AmbientSTAGESV1 SV2 SV3 SV4(HR1) (HR4) (HR3) (HR2)UR UF SPEED1OPEN CLOSED CLOSED CLOSED(De-energ) (Energ) (De-energ) (De-energ)Energ Energ De-energ2HP2CLOSEDCLOSED OPENControl(Energ)(De-energ) (Energ)(Energ)De-energ Energ Energ3OPEN OPEN CLOSED OPEN(De-energ) (De-energ) (De-energ) (Energ)De-energ Energ De-energDe-energ = De-energizedEnerg = EnergizedCLH(DR)Energ(De-energ)De-energ(Energ)Energ(De-energ)1-37 62-02461