Lennox Signature XP21 Series Installation And Service Procedure page 58

K5 COMPRESSOR MODULATING SOLENOID
COMPRESSOR INTERNAL SOLENOID (L34) TEST
PROCEDURE
IMPORTANT
When checking compressor for two−stage operation,
always cycle Y1 to Y2 from terminals on the
control integrated LSOM function
connections. DO NOT cycle second−stage (Y2) of
compressor by unplugging the 24VDC solenoid
the outdoor control integrated LSOM function (E34) end
of plug. The outdoor control integrated LSOM function
will only output a 6 to 18VDC signal which will be
insufficient voltage to pull the solenoid coil in for second
stage.
IMPORTANT
This performance check is ONLY valid on systems that
have clean indoor and outdoor coils, proper airflow over
coils, and correct system refrigerant charge. All compo-
nents in the system must be functioning proper to cor-
rectly perform compressor modulation operational
check. (Accurate measurements are critical to this test as
indoor system loading and outdoor ambient can affect
variations between low and high capacity readings).
XP21
Figure 28. K4 Compressor Modulating Solenoid
outdoor
to the room thermostat
input to
Page 58
Standard wiring without LSOM or icomfort t control with
built−in LSOM
Wiring with the LSOM or icomfort t control with the
built−in LSOM
Tools required
Refrigeration gauge set
D
Digital volt/amp meter
D
Electronic temperature thermometer
D
On-off toggle switch
D
STEP A Confirm low to high capacity compressor
operation
Procedure
1. Turn main power OFF to outdoor unit.
2. Adjust room thermostat set point above (heating op-
eration on heat pump) or below (cooling operation) the
room temperature.
3. Remove control access panel. Install refrigeration
gauges on unit. Attach the amp meter to the common
(black wire) wire of the compressor harness. Attach
thermometer to discharge line as close as possible to
the compressor.
4. Cycle main power ON.
5. Confirm Y1 operation only.
6. Allow pressures and temperatures to stabilize before
taking any measured reading (may take up to 10 min-
utes).