SERVICING
9
CHECKING VOLTAGE
1. Remove outer case, control panel cover, etc., from unit
being tested.
With power ON:
L
INE
V
OLTAGE
NOW
PRESENT
.
WARNING
2. Using a voltmeter, measure the voltage across terminals
L1 and L2 of the contactor for the heat pump condens-
er unit or at the field connections for the air handler or
heaters.
ComfortNet™ Ready Heat Pump Condenser Units:
Measure the voltage across the L1 and L2 lugs on the
unitary (UC) control.
3. No reading - indicates open wiring, open fuse(s) no pow-
er or etc., from unit to fused disconnect service. Repair
as needed.
4. With ample voltage at line voltage connectors, energize
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
HIGH VOLTAGE !
D
ISCONNECT
ALL
POWER
BEFORE
SERVICING
OR
INSTALLING
. M
ULTIPLE
POWER
SOURCES
MAY
BE
PRESENT
. F
AILURE
TO
DO
SO
MAY
CAUSE
PROPERTY
DAMAGE
,
PERSONAL
INJURY
OR
DEATH
.
WARNING
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
ComfortNet™ Ready Models
Communicating Thermostat Wiring: The maximum wire
length for 18 AWG thermostat wire is 250 feet.
THERMOSTAT AND WIRING
L
INE
V
OLTAGE
NOW
PRESENT
.
WARNING
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. Re-
pair or replace as necessary.
L
INE
V
OLTAGE
NOW
PRESENT
.
WARNING
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
HIGH VOLTAGE !
D
ISCONNECT
ALL
POWER
BEFORE
SERVICING
OR
INSTALLING
. M
ULTIPLE
POWER
SOURCES
MAY
BE
PRESENT
. F
AILURE
TO
DO
SO
MAY
CAUSE
PROPERTY
DAMAGE
,
PERSONAL
INJURY
OR
DEATH
.
WARNING
A step-down transformer (208/230 volt primary to 24 volt
secondary) is provided with each indoor unit. This al-
lows ample capacity for use with resistance heaters. The
outdoor sections do not contain a transformer (see note
below). (see indoor unit WIRING DIAGRAM)
D
ISCONNECT
ALL
POWER
BEFORE
SERVICING
.
WARNING
1. Remove control panel cover, or etc., to gain access to
transformer.
With power ON:
L
INE
V
OLTAGE
NOW
PRESENT
.
WARNING