Goodmans DSX User Manual

35

1. Remove outer case, control panel cover, etc., from unit

being tested.

With power ON:

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

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.

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.

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

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.

With power ON:

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.