Page 58
XP21
K5 COMPRESSOR MODULATING SOLENOID
Standard
wiring
without
LSOM
or
icomfort
control
with
built−in
LSOM
Wiring
with
the
LSOM
or
icomfort
control
with
the
built−in
LSOM
Figure 28. K4 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 outdoor
control integrated LSOM function to the room thermostat
connections. DO NOT cycle second−stage (Y2) of
compressor by unplugging the 24VDC solenoid input to
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).
Tools required
Refrigeration gauge set
Digital volt/amp meter
Electronic temperature thermometer
On-off toggle switch
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).
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