York DM036 Installation Manual

Also see for DM 036: Technical guide

Contents

York DM036 Installation Manual Manual pdf 44 page image

5011492-XIM-B-081544 Johnson Controls Unitary ProductsTroubleshootingCooling Troubleshooting GuideOn calls for cooling, if the compressors are operating but thesupply air blower motor does not energize after a short delay(the room thermostat fan switch is in the “AUTO” position).1. Turn the thermostat fan switch to the ON position. If thesupply air blower motor does not energize, go to Step 3.2. If the blower motor runs with the fan switch in the ONposition but will not run after the compressor has energizedwhen the fan switch is in the AUTO position, check theroom thermostat for contact between R and G in the AUTOposition during calls for cooling.3. If the supply air blower motor does not energize when thefan switch is set to ON, check that line voltage is beingsupplied to the contacts of the M2, contactor, and that thecontactor is pulled in. Check for loose wiring between thecontactor and the supply air blower motor.4. If M2 is pulled in and voltage is supplied to M2, lightly touchthe supply air blower motor housing. If it is hot, the motormay be off on internal protection. Cancel any thermostatcalls and set the fan switch to AUTO. Wait for the internaloverload to reset. Test again when cool.5. If M2 is not pulled in, check for 24 volts at the M2 coil. If 24volts are present at M2 but M2 is not pulled in, replace thecontactor.6. Failing the above, if there is line voltage supplied at M2, M2is pulled in, and the supply air blower motor still does notoperate, replace the motor.7. If 24 volts is not present at M2, check that 24 volts ispresent at the UCB supply air blower motor terminal,“FAN”. If 24 volts is present at the FAN, check for loosewiring between the UCB and M2.8. If 24 volts is not present at the “FAN” terminal, check for 24volts from the room thermostat. If 24 volts are not presentfrom the room thermostat, check for the following:a. Proper operation of the room thermostat (contactbetween R and G with the fan switch in the ON positionand in the AUTO position during operation calls).b. Proper wiring between the room thermostat and theUCB.c. Loose wiring from the room thermostat to the UCB.9. If 24 volts is present at the room thermostat but not at theUCB, check for proper wiring between the thermostat andthe UCB, i.e. that the thermostat G terminal is connected tothe G terminal of the UCB, and for loose wiring.10. If the thermostat and UCB are properly wired, replace theUCB.On a call for cooling, the supply air blower motor is operatingbut the compressor is not (the room thermostat fan switch is inthe “AUTO” position).1. If installed, check the position of the economizer blades. Ifthe blades are open, the economizer is providing freecooling and the compressors will not immediately operate.If both stages of cooling are requested simultaneously andthe economizer provides free cooling, following a shortdelay the compressor will be energized unless it is lockedout.2. If no economizer is installed or the economizer is notopening to provide free cooling and the compressor doesnot energize on a call for cooling, check for line voltage atthe compressor contactor, M1, and that the contactor ispulled in. Check for loose wiring between the contactor andthe 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 whencool.4. If M1 is not pulled in, check for 24 volts at the M1 coil. If 24volts are 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 is not present from the room thermostat, check forthe following:Troubleshooting of components may require openingthe electrical control box with the power connected tothe unit. Use extreme care when working with livecircuits! Check the unit nameplate for the correct linevoltage and set the voltmeter to the correct range beforemaking any connections with line terminals.When not necessary, shut off all electric power to theunit prior to any of the following maintenanceprocedures so as to prevent personal injury.Label all wires prior to disconnection when servicingcontrols. Wiring errors can cause improper anddangerous operation, which could cause injury to personand/or damage unit components. Verify properoperation after servicing.