SERVICING
11
Checking Voltage
WARNING
High Voltage!
Disconnect all power before servicing or
installing. Multiple power sources may be present.
Failure to do so may cause property damage,
personal injury or death.
1. Remove doors, control panel cover, etc. from unit
being tested.
With power ON:
WARNING
Line voltage now present.
2. Using a voltmeter, measure the voltage across
terminals L1 and L2 of the contactor.
3. No reading - indicates open wiring, open fuse(s) no
power or etc. from unit to fused disconnect service.
Repair as needed.
4. If incoming voltage is within the range listed in the
chart below, energize the unit.
5. Using a voltmeter, measure the voltage with the unit
starting and operating to determine if voltage is within
the range listed in the chart below.
6. If the voltage falls below the minimum voltage, check
the line wire size. Long runs of undersized wire can
cause low voltage. If the wire size is adequate, notify
the local power company regarding either low or high
voltage.
Unit Supply Voltage
Voltage
Min.
Max.
208/230
198
253
Checking Wiring
WARNING
High Voltage!
Disconnect all power before servicing or
installing. Multiple power sources may be present.
Failure to do so may cause property damage,
personal injury or death.
1. Check wiring visually for signs of overheating,
damaged insulation and loose connections.
2. Use an ohmmeter to check continuity of any
suspected open wires.
3. If any wires must be replaced, replace with
comparable gauge and insulation thickness.
Checking Thermostat and Wiring
Thermostat Wiring: The maximum wire length for 18 AWG
thermostat wire is 100 feet.
WARNING
Line voltage now present.
With power ON, thermostat calling for cooling:
1. Use a voltmeter to verify 24 volts present at
thermostat wires C and R.
2. If no voltage present, check transformer and
transformer wiring. If 24 volts present, proceed to
step 3.
3. Use a voltmeter to check for 24 volts at thermostat
wires C and Y.
4. No voltage indicates trouble in the thermostat, wiring
or external transformer source.
5. Check the continuity of the thermostat and wiring.
Repair or replace as necessary.
Indoor Blower Motor
With power ON:
WARNING
Line voltage now present.
1. Use a voltmeter to verify 24 volts present at
thermostat wires C and R.
2. If no voltage present, check transformer and
transformer wiring. If 24 volts present, proceed to
step 3.
3. Set fan selector switch at thermostat to “ON”
position.
4. With voltmeter, check for 24 volts at wires C and G.
5. No voltage, indicates the trouble is in the thermostat
or wiring.
6. Check the continuity of the thermostat and wiring.
Repair or replace as necessary.
Checking Transformer and Control Circuit
A step-down transformer (208/240 volt primary to 24 volt
secondary) is provided with each package unit. This allows
ample capacity for use with resistance heaters.
