Lennox Signature XP21 Series Installation And Service Procedure page 59

7. Record all of the readings for the Y1 demand on table
27.
8. Energize Y2 demand.
9. Allow pressures and temperatures to stabilize before
taking any measured reading (this may take up to 10
minutes).
10. Record all of the readings of Y2 demand on table 27.
11. Compare Y1 to Y2 readings. Readings match table 27
the proper operation is verified. If readings do not
match, proceed to Step A.
NOTE On new installations or installations that have
shut down for an extended period of time, if the compressor
does not cycle from low−stage to high−stage on the first at-
tempt, it may be necessary to recycle the compressor back
down to low−stage and back up to high−stage a few times in
order to get the bypass seals to properly seat. It might be
necessary to restrict the air flow over the indoor coil (heat-
ing) or outdoor coil (cooling) to maintain pressures high
enough to determine pressure differences between low
and high stages.
STEP 2 Verify Compressor Solenoid has Correct
Ohm Values.
1. Turn main power OFF to outdoor unit (main power and
low voltage).
2. Unplug the 2−pin solenoid plug from the fusite connec-
tion on the compressor.
SOLENOID PINS ON COMPRESSOR
FUSITE.
Figure 29. Testing
Figure 30.Solenoid Pins
3. Using a multi−meter set on ohms, check the ohms
valve of the solenoid coil in the compressor and
compare the value to table 26.
Table 26. Ohm Reading
Compressor Compressor
Family
ZPS*K4
ZPS*K5
NOTE − There are 2 ohm readings for the solenoids used in
the ZPS*K5 compressor.
STEP 3 Verify solenoid plug has DC output volt-
age.
1. Turn main power OFF to outdoor unit (main power and
low voltage).
2. Unplug the 2−pin solenoid plug from the fusite connec-
tion on the compressor.
3. Turn main power ON and input a 2−stage demand to
the outdoor unit.
4. Using the multi−meter set on DC volts, check the DC
volt value at the plug−in after the five (5) second Y2
delay. Voltage at the plug connections should be be-
tween 18 and 28 VDC for non−LSOM applications and
4 to 9 VDC in LSOM applications.
Page 59
Solenoid Resistance
Model
33.6 V
Source A
All Models
Source B
MULTI−METER LEADS INSERTED IN
COMPRESSOR SOLENOID PLUG−IN
Figure 31. Testing
1640 V
350 V
XP21