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SERVICING
35
S-1 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 terminals
L1 and L2 of the contactor for the condensing unit or at the
field connections for the air handler or heaters.
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, energize
the unit.
5. Measure the voltage with the unit starting and operating,
and determine the unit Locked Rotor Voltage. NOTE: If
checking heaters, be sure all heating elements are
energized.
Locked Rotor Voltage is the actual voltage available at
the compressor during starting, locked rotor, or a stalled
condition. Measured voltage should be above minimum
listed in chart below.
To measure Locked Rotor Voltage attach a voltmeter to
the run "R" and common "C" terminals of the compressor,
or to the T
1
and T
2
terminals of the contactor. Start the unit
and allow the compressor to run for several seconds, then
shut down the unit. Immediately attempt to restart the
unit while measuring the Locked Rotor Voltage.
6. Lock rotor voltage should read within the voltage tabula-
tion as shown. If the voltage falls below the minimum
voltage, check the line wire size. Long runs of undersized
wire can cause low voltage. If wire size is adequate, notify
the local power company in regard to either low or high
voltage.
VOLTAGE MIN. MAX.
460 437 506
208/230 198 253
UNIT SUPPLY VOLTAGE
NOTE: When operating electric heaters on voltages other
than 240 volts, refer to the System Operation section on
electric heaters to calculate temperature rise and air flow.
Low voltage may cause insufficient heating.
S-2 CHECKING WIRING
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.
S-3 CHECKING THERMOSTAT, WIRING, AND
ANTICIPATOR
THERMOSTAT WIRE SIZING CHART
LENGTH OF RUN
MIN. COPPER WIRE
GAUGE (AWG)
25 feet 18
50 feet 16
75 feet 14
100 feet 14
125 feet 12
150 feet 12
S-3A THERMOSTAT AND WIRING
WARNING
Line Voltage now present.
With power ON, thermostat calling for cooling
1. Use a voltmeter to check for 24 volts at thermostat wires
C and Y in the condensing unit control panel.
2. No voltage indicates trouble in the thermostat, wiring or
external transformer source.
3. 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. Set fan selector switch at thermostat to "ON" position.
2. With voltmeter, check for 24 volts at wires C and G.
3. No voltage indicates the trouble is in the thermostat or
wiring.