York ZF150 Installation Manual

Also see for Predator ZF078: Technical guide

518674-YIM-C-0610Johnson Controls Unitary Products 67remove any call for cooling at the thermostat or bydisconnecting the thermostat wiring at the Y2 UCBterminal. This will reset any compressor lock outs.NOTE: While the above step will reset any lock outs,compressor #1 will be held off for the ASCD, andcompressor #2 may be held off for a portion of theASCD. See the next step.10. If 24 volts is present at the UCB Y2 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 and releasethe TEST button to reset all ASCDs.11. The UCB can be programmed to lock out compressoroperation during free cooling and in low ambientconditions. These options are not enabled by default. Localdistributors can test the UCB for this programming.For units with factory installed economizers, the UCB isprogrammed to lock out compressor operation when theLAS set point is reached.For units without factory installed or with field installedeconomizers, the UCB allows compressor operation all thetime. This programming can be checked or changed by thelocal distributor.12. If none of the above corrected the error, test the integrity ofthe UCB. Disconnect the C2 terminal wire and jumper it tothe Y2 terminal. DO NOT jump the Y2 to C2 terminals. Ifthe compressor engages, the UCB has faulted.13. If none of the above correct the error, replace the UCB.On a call for cooling, the supply air blower motor andcompressor #2 are operating but compressor #1 is not (theroom thermostat fan switch is in the “AUTO” position):1. Compressor #2 is energized in place of compressor #1when compressor #1 is unavailable for cooling calls. Checkthe UCB for alarms indicating that compressor #1 is lockedout. Press and release the ALARMS button if the LED isnot flashing an alarm.2. Check for line voltage at the compressor contactor, M1,and that the contactor is pulled in. Check for loose wiringbetween the contactor and the compressor.3. If M1 is pulled in and voltage is supplied at M1, lightly touchthe compressor housing. If it is hot, the compressor may beoff on inherent protection. Cancel any calls for cooling andwait for the internal overload to reset. Test again when cool.4. If M1 is not pulled in, check for 24 volts at the M1 coil. If 24volts is present and M1 is not pulled in, replace thecontactor.5. Failing the above, if voltage is supplied at M1, M1 is pulledin, and the compressor still does not operate, replace thecompressor.6. If 24 volts is not present at M1, check for 24 volts at theUCB terminal, C1. If 24 volts is present, check for loosewiring between C1 and the compressor contactor.7. If 24 volts is not present at the C1 terminal, check for 24volts from the room thermostat at the UCB Y1 terminal. If24 volts are not present at the UCB Y1 terminal, the UCBmay have faulted. Check for 24 volts at the Y1 ECONterminal. If 24 volts is not present at Y1 “ECON”, the UCBhas faulted. The UCB should de-energize all compressorson a loss of call for the first stage of cooling, i.e. a loss if 24volts at the Y1 terminal.8. If 24 volts are present at the UCB Y1 terminal, thecompressor may be out due to an open high-pressureswitch, low-pressure switch, or freezestat. Check for 24volts at the HPS1, LPS1, and FS1 terminals of the UCB. Ifa switch has opened, there should be a voltage potentialbetween the UCB terminals, e.g. if LPS1 has opened, therewill be a 24-volt potential between the LPS1 terminals.9. If 24 volts is present at the UCB Y1 terminal and none ofthe protection switches have opened, the UCB may havelocked out the compressor for repeat trips. The UCBshould be flashing a code. If not, press and release theALARMS button on the UCB. The UCB will flash the lastfive alarms on the LED. If the compressor is locked out,remove any call for cooling. This will reset any compressorlock outs.NOTE: While the above step will reset any lock outs,compressor #2 will be held off for the ASCD, andcompressor #1 may be held off for a portion of theASCD. See the next 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 and releasethe 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, repeattrip lock out, or ASCD, the economizer terminals of the UCBmay be improperly wired. Check for 24 volts at the Y1 “OUT”terminal of the UCB. If 24 volts is present, trace the wiringfrom Y1 “OUT” for incorrect wiring. If 24 volts is not presentat the Y1 “OUT” terminal, the UCB must be replaced.12. For units without 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, thejumper in the Mate-N-Lock plug, and in the wiring from theMate-N-Lock plug to the Y1 “ECON” terminal.For units with economizers: If 24 volts is present at the Y1“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 economizer Mate-N-Lock plugs, loose wiring from the Mate-N-Lock plug tothe economizer, back to the Mate-N-Lock plug, and fromthe Mate-N-Lock plug to the Y1 “ECON” terminal. Theeconomizer control may have faulted and is not returningthe 24 volts to the Y1 “ECON” terminal even though the

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