TEST
50
70
90
100
P1
40
45
50
55
P3
Page 35
XPG20 SERIES
2.
Actuation of Defrost Cycle
The defrost cycle starts
when the following occurs:
S
Reversing valve
O
terminal is de−energized
S
Y1 circuit is energized
S
Coil temperature is below 35°F (2°C),
S
DCB starts logging the compressor run time.
Calibration success depends on stable system
temperatures during the 20−minute calibration period.
If the board fails to calibrate, another defrost cycle will
be initiated after 45 minutes of heating mode
compressor run time. Once the DCB is calibrated, it
initiates a demand defrost cycle when the difference
between the clear coil and frosted coil temperatures
exceeds the maximum difference allowed by the
control OR after six hours of heating mode
compressor run time has been logged since the last
defrost cycle.
NOTE If ambient or coil fault is detected, the board
will not execute the TEST mode.
3.
Termination
The defrost cycle ends when the coil
temperature exceeds the termination temperature or
after 14 minutes of defrost operation. If the defrost is
terminated by the 14−minute timer, another defrost
cycle will be initiated after 30 minutes of run time.
4.
Test Mode
When
Y1
is energized and
24V power is being applied to the board,
a test cycle can be initiated by placing the
termination temperature jumper across
the
TEST
pins for 2 to 5 seconds. If the
jumper remains across the
TEST
pins
longer than five seconds, the control will
ignore the test pins and revert to normal
operation. The jumper will initiate one
cycle per test.
NOTE Coil sensor temperature must be below 35ºF
before the DCB will initiate a
TEST
defrost
.
Each test pin shorting will result in one test event.
For each
TEST
the jumper must be removed for at
least one second and reapplied. Refer to flow chart
(Figure 23) for TEST operation.
NOTE
For the test to proceed, the
Y1
terminal on
the DCB must have 24VAC applied to it and the
O
terminal must read 0vac.
SECOND−STAGE OPERATION
If the board receives a call for second−stage compressor
operation
Y2
in heating or cooling mode and the first-stage
compressor output is active, the second-stage
compressor solenoid output will be energized by the
LSOM.
NOTE Figure 14 illustrates the correct
Y2
field wiring
configuration.
NOTE The LSOM has a five second delay between
Y2
being powered and the solenoid energizing.
If first-stage compressor output is active in heating mode
and the outdoor ambient temperature is below the selected
compressor lock−in temperature, the second-stage
compressor solenoid output will be energized even without
a
Y2
room thermostat input.
If the jumper is not connected to one of the
temperature selection pins on
P3 (40, 45, 50,
55°F)
, the default lock−in temperature of 40°F
(4.5°C) will be used.
The board de−energizes the second-stage
compressor solenoid output immediately when
the
Y2
signal is removed or the outdoor ambient
temperature is 5°F above the selected compressor lock−in
temperature, or the first-stage compressor output is
de−energized for any reason.
SECOND−STAGE COMPRESSOR CHECKOUT
Use this check-out procedure to verify part- and full-load
capacity operation of two-stage modulation compressor.
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 components in the system must be
functioning proper to correctly 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
S
Refrigeration gauge set
S
Digital volt/amp meter
S
Electronic temperature thermometer
S
On-off toggle switch
PROCEDURE
1. Turn main power OFF to outdoor unit.
2. Adjust room thermostat set point 5ºF above (heating
operation) or 5ºF 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. Turn toggle switch OFF. Install switch in series with Y2
wire from room thermostat (see note ** in the
Field
Operational Checklist
on page 42).
5. Cycle main power ON.
6. Allow pressures and temperatures to stabilize before
taking any measured reading (may take up to 10
minutes).
7. Record all of the readings for the
Y1
demand.
8. Close switch to energize
Y2
demand. Verify power is
going to compressor solenoid (see note ** in the
Field
Operational Checklist
on page 42).
