SERVICING
9
CHECKING VOLTAGE
1. Remove outer case, control panel cover, etc., from
unit being tested.
With power ON:
WARNING
Line voltage now present.
2. Using a voltmeter, measure the voltage across ter-
minals L1 and L2 of the contactor for the heat pump
condenser unit or at the field connections for the air
handler or heaters.
Measure the voltage across the L1 and L2 lugs on the
unitary (UC) control.
3. No reading - indicates open wiring, open fuse(s) no
power or etc., from unit to fused disconnect service.
Repair as needed.
4. With ample voltage at line voltage connectors, ener-
gize the unit.
Voltage
Min.
Max
208/230
197
253
Unit Supply Voltage
NOTE
: When operating electric heaters on voltages other
than 240 volt, refer to the System Operation section on
electric heaters to calculate temperature rise and air flow.
Low voltage may cause insufficient heating.
CHECKING WIRING
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper-
ty damage, personal injury or death.
1. Check wiring visually for signs of overheating, dam-
aged insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspect-
ed open wires.
3. If any wires must be replaced, replace with compara-
ble gauge and insulation thickness.
CHECKING THERMOSTAT AND WIRING
Communicating Thermostat Wiring: The maximum wire
length for 18 AWG thermostat wire is 250 feet.
THERMOSTAT AND WIRING
WARNING
Line voltage now present.
With power ON, thermostat calling for cooling/heating.
1. Use a voltmeter to check for 24 volt at thermostat
wires C and R in the indoor unit control panel.
2. No voltage indicates trouble in the thermostat, wiring
or transformer source.
3. Check the continuity of the thermostat and wiring.
Repair or replace as necessary.
WARNING
Line voltage now present.
RESISTANCE HEATERS
With power ON:
1. Set room thermostat to a higher setting than room
temperature so both stages call for heat.
2. With voltmeter, check for 24 volt at each heater relay.
3. No voltage indicates the trouble is in the thermostat
or wiring.
4. Check the continuity of the thermostat and wiring.
Repair or replace as necessary.
NOTE:
Consideration must be given to how the heaters
are wired (O.D.T. and etc.). Also safety devices must be
checked for continuity.
CHECKING TRANSFORMER AND CONTROL CIRCUIT
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or in-
stalling this unit. Multiple power sources may
be present. Failure to do so may cause proper-
ty damage, personal injury or death.
A step-down transformer (208/230 volt primary to 24 volt
secondary) is provided with each indoor unit. This allows
ample capacity for use with resistance heaters. The outdoor
sections do not contain a transformer (See note below).
(See indoor unit WIRING DIAGRAM).
WARNING
Disconnect power supply before servicing.
