Lennox Merit Series 13HPX User Manual

(T2), or 90 (T3) minutes (see figure 20), The defrost tim-
ing jumper is factory-installed to provide a 60-minute de-
frost interval. If the timing selector jumper is not in place,
the control defaults to a 90-minute defrost interval. The
maximum defrost period is 14 minutes and cannot be ad-
justed.
A TEST option is provided for troubleshooting, The TEST
mode may be started any time the unit is in the heating
mode and the defrost thermostat is closed or jumper-
ed. If the jumper is in the TEST position at power-up, the
control will ignore the test pins, When the jumper is placed
across the TEST pins for two seconds, the control will en-
ter the defrost mode, If the jumper is removed before an
additional 5-second period has elapsed (7 seconds total),
the unit will remain in defrost mode until the defrost ther-
mostat opens or 14 minutes have passed. If the jumper is
not removed until after the additional 5-second period has
elapsed, the defrost will terminate and the test option will
not function again until the jumper is removed and re-ap-
plied,
COMPRESSOR DELAY
The defrost board has a field-selectable function to reduce
occasional sounds that may occur while the unit is cycling
in and out of the defrost mode. The compressor will be
cycled off for 30 seconds going in and out of the defrost
mode when the compressor delay jumper is removed.
NOTE - The 30-second compressor feature is ignored
when jumpering the TEST pins.
TIME DELAY
The timed-off delay is five minutes long. The delay helps to
protect the compressor from short-cycling in case the pow-
er to the unit is interrupted or a pressure switch opens, The
delay is bypassed by placing the timer select jumper
across the TEST pins for 0,5 seconds,
Pressure Switch Circuit
The defrost control incorporates two pressure switch cir-
cuits. The high pressure switch ($4) is factory-connected
to the board's Ht PS terminals (see figure 20). The board
also includes a low pressure, or loss-of-charge-pressure,
switch ($87). Switches are shown in wiring diagram (figure
5, page 5) and in figure 20.
During a single demand cycle, the defrost control will lock
out the unit after the fifth time that the circuit is interrupted
by any pressure switch wired to the control board. In addi-
tion, the diagnostic LEDs will indicate a locked-out pres-
sure switch after the fifth occurrence of an open pressure
switch (see Table 13). The unit will remain locked out until
power to the board is interrupted, then re-established or
until the jumper is applied to the TEST pins for 0.5 sec-
onds.
NOTE - The defrost control board ignores input from the
low-pressure switch terminals as follows:
• during the TESTmode,
• during the defrost cycle,
• during the 90-second start-up period,
• and for the first 90 seconds each time the reversing
valve switches heat/cool modes.
Diagnostic LEDs
The defrost board uses two LEDs for diagnostics. The
LEDs flash a specific sequence according to the condition.
Table 13. Defrost Control Board Diagnostic LED
Mode Green LED (DS2) Red LED (DS1)
No power to con- OFF OFF
trol
Normal operation / Simultaneous Slow FLASH
power to control
Anti-short cycle Alternating Slow FLASH
lockout
Low pressure OFF Slow FLASH
switch fault
Low pressure OFF ON
switch lockout
High pressure Slow FLASH OFF
switch fault
High pressure ON OFF
switch lockout
kWARNING
Maintenance and service must be performed by a qualified
installer or service agency. At the beginning of each cool-
ing season, the system should be checked as follows:
OUTDOOR UNIT
1, Clean and inspect outdoor coil (may be flushed with a
water hose). Ensure power is off before cleaning.
2, Outdoor unit fan motor is pre-lubricated and sealed,
No further lubrication is needed.
3, Visually inspect all connecting lines, joints and coils for
evidence of oil leaks.
4, Check all wiring for loose connections,
5. Check for correct voltage at unit (unit operating),
6, Check amp draw on outdoor fan motor.
Unit nameplate Actual
7, Inspect drain holes in coil compartment base and
clean if necessary,
NOTE - If insufficient heating or cooling occurs, the unit
should be gauged and refrigerant charge should be
checked.
INDOOR COIL
1. Clean coil if necessary.
2, Check connecting lines, joints and coil for evidence of
oil leaks,
3. Check condensate line and clean if necessary,
INDOOR UNIT
1. Clean or change filters,
2, Lennox blower motors are prelubricated and permanent-
ly sealed, No more lubrication is needed,
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Lennox Merit Series 13HPX Specifications

General

Brand	Lennox
Model	Merit Series 13HPX
Category	Heat Pump
Language	English