York DM090 installation manual Cooling Troubleshooting Guide

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035-17311-003-A-0704

COOLING TROUBLESHOOTING GUIDE

On calls for cooling, if the compressors are operating but the supply 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 the supply air blower motor does not energize, go to Step 3.

2.If the blower motor runs with the fan switch in the ON position but will not run after the first compressor has energized when the fan switch is in the AUTO position, check the room thermostat for contact between R and G in the AUTO position during calls for cooling.

3.If the supply air blower motor does not energize when the fan switch is set to ON, check that line voltage is being supplied to the contacts of the M3, contactor, and that the contactor is pulled in. Check for loose wiring between the contactor and the supply air blower motor.

4.If M3 is pulled in and voltage is supplied to M3, lightly touch the supply air blower motor housing. If it is hot, the motor may be off on internal protection. Cancel any thermostat calls and set the fan switch to AUTO. Wait for the internal overload to reset. Test again when cool.

5.If M3 is not pulled in, check for 24 volts at the M3 coil. If 24 volts are present at M3 but M3 is not pulled in, replace the contactor.

6.Failing the above, if there is line voltage supplied at M3, M3 is pulled in, and the supply air blower motor still does not operate, replace the motor.

7.If 24 volts is not present at M3, check that 24 volts is present at the UCB supply air blower motor terminal, “FAN”. If 24 volts is present at the FAN, check for loose wiring between the UCB and M3.

8.If 24 volts is not present at the “FAN” terminal, check for 24 volts from the room thermostat. If 24 volts are not present from the room thermostat, check for the follow- ing:

a.Proper operation of the room thermostat (contact between R and G with the fan switch in the ON posi- tion and in the AUTO position during operation calls).

b.Proper wiring between the room thermostat and the UCB, and

c.Loose wiring from the room thermostat to the UCB

9.If 24 volts is present at the room thermostat but not at the UCB, check for proper wiring between the thermostat and the UCB, i.e. that the thermostat G terminal is con- nected to the G terminal of the UCB, and for loose wir- ing.

10.If the thermostat and UCB are properly wired, replace the UCB.

On calls for cooling, the supply air blower motor is operating but compressor #1 is not (the room thermostat fan switch is in the “AUTO” position):

1.If installed, check the position of the economizer blades. If the blades are open, the economizer is providing free cooling and the compressors will not immediately oper- ate. If both stages of cooling are requested simulta- neously and the economizer provides free cooling, following a short delay compressor #1 will be energized unless it is locked out. If compressor #1 is locked out, compressor #2 is energized. Compressor #2 is always energized in place of compressor #1 when compressor #1 is requested but locked out.

2.If no economizer is installed or the economizer is not opening to provide free cooling and compressor #1 does not energize on a call for cooling, check for line voltage at the compressor contactor, M1, and that the contactor is pulled in. Check for loose wiring between the contac- tor and the compressor.

3.If M1 is pulled in and voltage is supplied at M1, lightly touch the compressor housing. If it is hot, the compres- sor may be off on inherent protection. Cancel any calls for cooling and wait 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 24 volts are present and M1 is not pulled in, replace the contactor.

5.Failing the above, if voltage is supplied at M1, M1 is pulled in, and the compressor still does not operate, replace the compressor.

6.If 24 volts is not present at M1, check for 24 volts at the UCB terminal, C1. If 24 volts is present, check for loose wiring between C1 and the compressor contactor.

7.If 24 volts is not present at the C1 terminal, check for 24 volts from the room thermostat at the UCB Y1 terminal. If 24 volts is not present from the room thermostat, check for the following:

a.24 volts at the thermostat Y1 terminal

b.Proper wiring between the room thermostat and the UCB, i.e. Y1 to Y1, Y2 to Y2, and

c.Loose wiring from the room thermostat to the UCB

8.If 24 volts is present at the UCB Y1 terminal, the com- pressor may be out due to an open high-pressure switch, low-pressure switch, or freezestat. Check for 24 volts at the HPS1, LPS1, and FS1 terminals of the UCB. If a switch has opened, there should be a voltage potential between the UCB terminals, e.g. if LPS1 has opened, there will be a 24-volt potential between the LPS1 termi- nals.

9.If 24 volts is present at the UCB Y1 terminal and none of the protection switches have opened, the UCB may have

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Contents Installation Manual Table of Contents List of Figures List of Tables General Safety ConsiderationsInspection ReferenceNomenclature ½ 12½ Ton Predator Model Number NomenclatureNOMENCLATURE, Additonal Options Johnson UNT Controller, DFS, APS & Phase Monitor Technicoat Condenser Coil, Phase Monitor, & Coil Guard Preceding Installation InstallationInstallation Safety Information Rigging and Handling Unit Temperature LimitationsLocation Length of Forks Must be a Minimum of 60 Inches Point Load WeightDetail C Detail B Detail aBottom Duct Openings from Above Duct Covers DuctworkSide Panels with Hole Plugs Condensate Drain Control Wire Sizes Thermostat WiringPower and Control Wiring Power Wiring DetailElectronic Thermostat Field Wiring RLA 380 11.5 75.0 Electrical Data DM120 10 TON with Power Convenience OutletMinimum Supply AIR CFM OPTIONS/ACCESSORIESPhysical Data Adjustments and Information Economizer and Power Exhaust SET PointEnthalpy SET Point Chart Blower Rotation PhasingSupply AIR Limitations Belt Tension1/2 TON Optional Motor Down Shot Blower PERFORMANCE* † 1/2 TON Standard Motor Down Shot Blower PERFORMANCE* †10 TON Optional Motor Down Shot Blower PERFORMANCE* † 10 TON Standard Motor Down Shot Blower PERFORMANCE* †12-1/2 TON Optional Motor Down Shot Blower PERFORMANCE* † 12-1/2 TON Standard Motor Down Shot Blower PERFORMANCE* †1/2 TON Optional Motor Side Shot Blower PERFORMANCE* † 1/2 TON Standard Motor Side Shot Blower PERFORMANCE* †10 TON Standard Motor Down Shot Blower PERFORMANCE* † 12-1/2 TON Optional Motor Side Shot Blower PERFORMANCE* † 12-1/2 TON Standard Motor Side Shot Blower PERFORMANCE* †AIR Balance Indoor Blower SpecificationsChecking AIR Quantity Method ONE Method TWODRY Coil Delta P Supply AIR Drive Adjustment Additional Static Resistance OperationMotor Sheave Datum Diameters Sequence of Operations OverviewCooling Sequence of Operation Compressor Protection Safety ControlsElectric Heat Limit Setting Electric Heating Operation ErrorsElectric Heating Sequence of Operations Electric Heat Antictpator SetpointsCharging the Unit START-UP Cooling12.5 TON Standard Efficiency Superheat Charging 10 TON Standard Efficiency Superheat ChargingPredator Flash Codes Normal Maintenance TroubleshootingGeneral Unit Control Board Flash Codes Basic Troubleshooting FlowchartCooling Troubleshooting Guide Unitary Products Group 035-17311-003-A-0704 Unitary 5005 Norman Products York Group Drive 73069