York PREDATOR DM090 Installation Manual

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035-17311-003-A-070442 Unitary Products Grouplocked out the compressor for repeat trips. The UCBshould be flashing an alarm code. If not, press andrelease the ALARMS button on the UCB. The UCB willflash the last five alarms on the LED. If the compressoris locked out, cancel any call for cooling. This will resetany compressor lock outs.NOTE: While the above step will reset any lockouts, com-pressor #1 may be held off for the ASCD. See thenext step.10. If 24 volts is present at the UCB Y1 terminal and none ofthe switches are open and the compressor is not lockedout, the UCB may have the compressor in an ASCD.Check the LED for an indication of an ASCD cycle. TheASCD should time out within 5 minutes. Press andrelease the TEST button to reset all ASCDs.11. If 24 volts is present at the UCB Y1 terminal and thecompressor is not out due to a protective switch trip,repeat trip lock out, or ASCD, the economizer terminalsof the UCB may be improperly wired. Check for 24 voltsat the Y1 “OUT” terminal of the UCB. If 24 volts ispresent, trace the wiring from Y1 “OUT” for incorrect wir-ing. If 24 volts is not present at the Y1 “OUT” terminal,the UCB must be replaced.12. For units without economizers: If 24 volts is present atthe Y1 OUT terminal, check for 24 volts at the Y1“ECON” terminal. If 24 volts is not present, check forloose wiring from the Y1 “OUT” terminal to the Mate-N-Lock plug, the jumper in the Mate-N-Lock plug, and inthe wiring from the Mate-N-Lock plug to the Y1 “ECON”terminal.13. For units with economizers: If 24 volts is present at theY1 “OUT” terminal, check for 24 volts at the Y1 “ECON”terminal. If 24 volts is not present, check for loose wiringfrom the Y1 “OUT” terminal to the Mate-N-Lock plug, apoor connection between the UCB and economizerMate-N-Lock plugs, loose wiring from the Mate-N-Lockplug to the economizer, back to the Mate-N-Lock plug,and from the Mate-N-Lock plug to the Y1 “ECON” termi-nal. If nothing is found, the economizer control may havefaulted and is failing to return the 24-volt “call” to the Y1“ECON” terminal even though the economizer is not pro-viding free cooling. To test, disconnect the Mate-N-Locksand jumper between the WHITE and YELLOW wires ofthe UCB’s Mate-N-Lock plug. If compressor #1 ener-gizes, there is a fault in the economizer wiring or theeconomizer control.14. The UCB can be programmed to lock out compressoroperation during free cooling and in low ambient condi-tions. These options are not enabled by default. LocalYork distributors can test the UCB for this programming.15. If none of the above corrected the error, test the integrityof the UCB. Disconnect the C1 terminal wire and jumperit to the Y1 terminal. DO NOT jump the Y1 to C1 termi-nals. If the compressor engages, the UCB has faulted.16. If none of the above correct the error, replace the UCB.On calls for the second stage of cooling, the supply air blowermotor and compressor #1 are operating but compressor #2 isnot (the room thermostat fan switch is in the “AUTO” posi-tion):1. If installed, check the position of the economizer blades.If the blades are open, the economizer is providing freecooling. If the second stage of cooling is requested, fol-lowing a short delay, compressor #1 will be energizedunless it is locked out. Typically, compressor #2 is ener-gized only during free cooling if the call for the secondstage of cooling persists for 20 minutes.2. Compressor #2 will not energize simultaneously withcompressor #1 if a call for both stages of cooling isreceived. The UCB delays compressor #2 by 30 sec-onds to prevent a power surge. If after the delay com-pressor #2 does not energize on a second stage call forcooling, check for line voltage at the compressor contac-tor, M2, and that the contactor is pulled in. Check forloose wiring between the contactor and the compressor.3. If M2 is pulled in and voltage is supplied at M2, lightlytouch the compressor housing. If it is hot, the compres-sor may be off on inherent protection. Cancel any callsfor cooling and wait for the internal overload to reset.Test again when cool.4. If M2 is not pulled in, check for 24 volts at the M2 coil. If24 volts is present and M2 is not pulled in, replace thecontactor.5. Failing the above, if voltage is supplied at M2, M2 ispulled in, and the compressor still does not operate,replace the compressor.6. If 24 volts is not present at M2, check for 24 volts at theUCB terminal, C2. If 24 volts are present, check forloose wiring between C2 and the compressor contactor.7. If 24 volts is not present at the C2 terminal, check for 24volts from the room thermostat at the UCB Y2 terminal.If 24 volts is not present from the room thermostat, checkfor the following:a. 24 volts at the thermostat Y2 terminalb. Proper wiring between the room thermostat and theUCB, i.e. Y1 to Y1, Y2 to Y2, andc. Loose wiring from the room thermostat to the UCB8. If 24 volts is present at the UCB Y2 terminal, the com-pressor may be out due to an open high-pressure switch,low-pressure switch, or freezestat. Check for 24 volts atthe HPS2, LPS2, and FS2 terminals of the UCB. If aswitch has opened, there should be a voltage potentialbetween the UCB terminals, e.g. if LPS2 has opened,there will be 24 volts of potential between the LPS2 ter-minals.

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