Carrier HS070-160 Troubleshooting Manual

Also see for 30HR070: Installation, Start-Up and Service Instructions Installation, Start-Up and Service Instructions

Contents

Table 3 - Thermistors CONTROL SEQUENCEThe control power (115-l-60 for 60-Hz units; 230-l-50for 50-Hz units) must be supplied directly from a separatesource through a code-approved fused disconnect to theLl and L2 terminals of unit power teminal block.NOTE: There is no switch or circuit breaker; only fuses. Ifthe control power feed is live, so is the circuit.Crankcase heaters are wired into the control circuit.They are always operative as long as control circuitpower is on even though unit may be off because ofsafety device action. Heaters are wired so they are on onlywhen their respective compressors are cycled off.A,f’tor a prnlonged shutdoun, the crankcause heatersshould be on ,for 24 hours hqfbre starting the unit.When power is supplied to control circuit, unit is readyfor operation providing all safety devices are satisfied,interlocks are closed and instructions on warning labelshave been followed.If schedule function is used, refer to page 11 for detailson control operation.Off Cycle - During unit off cycle when the RUN;STANDBY switch is in the STANDBY position, thecrankcase heaters and the control system are energized.The electronic expansion valves are also energized.(NOTE: The control circuit power must be on at all timeseven when the main unit power is off.)Start-Up - When the RUN/STANDBY switch ismoved from the STANDBY to the RUN position andthere is a call for cooling, after l-l /2 to 3 minutes havepassed the first compressor will start unloaded, The firstcircuit to start may be circuit A or B due to the automaticlead/ lag feature.Capacity Control - (See Table 4.) The rate at whichthe compressors are turned on will depend on the leavingwater temperature difference from the set point, the rateof change of leaving water temperature, the return watertemperature and the number of compressor stages on.The control is primarily from leaving water temperatureand the other factors are used as compensation.SEQUENCE -- On a caiI for cooling, the controI systemstarts the initial compressor. The control will randomlyselect either circuit A or B. The liquid line solenoid valveremains closed for 10 seconds after the initial compressoron that refrigeration circuit starts. This permits a pump-out cycle at start-up to minimize refrigerant floodbackto the compressor. If the compressor in that refrigerationcircuit has run in the 15 minutes before the call forcooling, the pumpout cycle is bypassed.After pumpout, the liquid line solenoid valve opens andthe electronic expansion valve starts to open.The electronic expansion valve will open gradually toprovide a controlled start-up to prevent liquid floodbackto the compressor. Also during this period, the oil pres-sure switch will be bypassed for one minute.As additional cooling is required, the control systemwill ramp up through the capacity steps available until theload requirement is satisfied. As capacity steps are addedcompressors are brought on line, alternating between thelead and lag refrigerant circuits. As explained previously,the speed at which capacity is increased or decreased iscontrolled by the temperature deviation from the setpoint and the rate of change in the chilled watertemperature.Table 4 - Capacity Control StepsSEQUENCE A ENCE 3er Cylinderszlzqxi7c-26a1 0E4a1 01 21 41 64a1 01 21 61 84 81:::::4a10:;hi2 24a1 01 21 61%2 22 44a1 01 21 6:;2 4c-rot.4:1 01 21 441:13141 6ii1 0121 6184 a10121 41 61 82 041:1 21 4162 02 24a1 01 21 6:;2 448iif::2 22 4?r CylindersEiiqTm-C o m p r42--44---44---66--44t-6:682----------------t---44-----:---E-UNIT3 0 H R3 0 H S:ONTRS T E P S %C a p .1 4 . 34 2 . 95 7 . 27 1 . 28 5 . 7100.02 5 . 05 0 . 06 2 . 57 5 . 08 7 . 5100.0%Cap.2&.64 2 . 95 7 . 27 1 . 28 5 . 70 0 . 02 5 . 05 0 . 06 2 . 57 5 . 08 7 . 50 0 . 02 2 . 24 4 . 45 5 . 56 6 . 78 8 . 8‘00.02 0 . 04 0 . 05 0 . 06 0 . 07 0 . 080.09 0 . 0100.01 8 . 23 6 . 34 5 . 45 4 . 56 3 . 67 2 . 79 0 . 9t 00.01 6 . 63 3 . 34 1 . 65 0 . 06 6 . 77 5 . 09 1 . 6100.019.03 8 . 04 7 . 65 7 . 06 9 . 07 8 . 69 0 . 4100.0C o m p rB2-----------44:-4444--:66---:E-0 7 00 8 02 2 . 24 4 . 45 5 . 56 6 . 78 8 . 81 0 0 . 02 0 . 04 0 . 05 0 . 06 0 . 07 0 . 08 0 . 09 0 . 0100.01 8 . 23 6 . 34 5 . 45 4 . 57 2 . 78 1 . 89 0 . 9100.00901 0 01 1 01 6 . 63 3 . 34 1 . 65 0 . 06 6 . 77 5 . 09 1 . 6100.01 9 . 03 8 . 04 7 . 65 7 . 06 9 . 07 8 . 69 0 . 4100.0120,1 6 01 4 0NOTE: Circuits andfrom front of unit.compressors designated from ieft to right when viewed4