7.Measure evaporator fan motor's amp draw.
8.Set the room thermostat fan switch to off.
9.Turn unit electrical power off.
OPERATING INSTRUCTIONS
1.Turn unit electrical power on.
2.Set the room thermostat setting to lower than the room temperature.
3.First stage compressors will energize after the
4.The second stage of the thermostat will energize second stage compressor if needed.
POST START CHECK LIST
1.Verify proper system pressures for both circuits.
2.Measure the temperature drop across the evapora- tor coil.
3.Measure the system Amperage draw across all legs of 3 phase power wires.
4.Measure the condenser fan amp draw.
SHUT DOWN
1.Set the thermostat to highest temperature setting.
2.Turn off the electrical power to the unit.
TROUBLESHOOTING
COOLING TROUBLESHOOTING GUIDE
Troubleshooting of components may require opening the electrical control box with the power connected to the unit. Use extreme care when working with live circuits! Check the unit nameplate for the correct line voltage and set the voltmeter to the correct range before making any connections with line termi- nals.
When not necessary, shut off all electric power to the unit prior to any of the following mainte- nance procedures so as to prevent personal injury.
Label all wires prior to disconnection when ser- vicing controls. Wiring errors can cause improper and dangerous operation, which could cause injury to person and/or damage unit components. Verify proper operation after servicing.
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 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 M2, contactor, and that the contactor is pulled in. Check for loose wiring between the contactor and the sup- ply air blower motor.
4.If M2 is pulled in and voltage is supplied to M2, lightly touch the supply air blower motor housing. If it is hot, the motor may be off on internal protec- tion. Cancel any thermostat calls and set the fan switch to AUTO. Wait for the internal overload to reset. Test again when cool.
5.If M2 is not pulled in, check for 24 volts at the M2 coil. If 24 volts are present at M2 but M2 is not pulled in, replace the contactor.
6.Failing the above, if there is line voltage supplied at M2, M2 is pulled in, and the supply air blower motor still does not operate, replace the motor.
7.If 24 volts is not present at M2, check that 24 volts is present at the UCB supply air blower motor ter- minal, “FAN”. If 24 volts is present at the FAN, check for loose wiring between the UCB and M2.
32 | Unitary Products Group |
