Lennox Elite Series Installation Instructions Manual page 24

Table 12. Defrost Control Board Diagnostic LEDs
DS2 DS1
Green Red Condition/Code Possible Cause(s) Solution
OFF OFF Power problem No power (24V) to board terminals 1 Check control transformer power (24V).
R & C or board failure. 2 If power is available to board and LED(s) do
not light, replace board.
Simultaneous Normal operation Unit operating normally or in stand- None required.
SLOW Flash by mode.
Alternating SLOW 5-minute anti-short cycle Initial power up, safety trip, end of None required (Jumper TEST pins to override)
Flash delay room thermostat demand.
Simultaneous Ambient Sensor Problem Sensor being detected open or shorted or out of temperature range. Board will revert to
FAST Flash time/temperature defrost operation. (System will still heat or cool).
Alternating Coil Sensor Problem Sensor being detected open or shorted or out of temperature range. Board will not per-
FAST Flash form demand or time/temperature defrost operation. (System will still heat or cool).
ON ON Circuit Board Failure doeslndicateSnot clear,that boardreplacehaSboard.internal component failure. Cycle 24 volt power to board. If code
Table 13. Defrost Control Board Diagnostic Fault and Lockout Codes
DS2 DS1
Green Red Condition/Code Possible Cause(s) Solution
(Each fault adds 1 strike to that code's counter; 5 strikes per code = LOCKOUT)
OFF
OFF
SLOW
Flash
ON
SLOW Low Pressure Fault
Flash
ON Low Pressure LOCKOUT
OFF High Pressure Fault
OFF High Pressure LOCKOUT
1 Restricted air flow over indoor or
outdoor coil.
2 Improper refrigerant charge in
system.
3 Improper metering device
installed or incorrect operation
of metering device.
4 Incorrect or improper sensor
location or connection to sys-
tem.
1 Remove any blockages or restrictions from
coils and/or fans. Check indoor and outdoor
fan motor for proper current draws.
2 Check system charge using approach and
subcooling temperatures.
3 Check system operating pressures and
compare to unit charging charts.
4 Make sure all pressure switches and sensors
have secure connections to system to prevent
refrigerant leaks or errors in pressure and
temperature measurements.
SLOW ON Discharge Line Temperature
Flash Fault
FAST
Flash
ON Discharge Line Tempera-
ture LOCKOUT
This code detects shorted sensor or high discharge temperatures. If the discharge line
temperature exceeds a temperature of 300°F (148°C) during compressor operation, the
board will de-energize the compressor contactor output (and the defrost output if active).
The compressor will remain off until the discharge temperature has dropped below 225°F
(107°C).
OFF Fast Discharge Sensor Fault
Flash
Fast OFF Discharge Sensor
Flash LOCKOUT
The board detects open sensor or out of temperature sensor range. This fault is detected
by allowing the unit to run for 90 seconds before checking sensor resistance. If the sen-
sor resistance is not within range after 90 seconds, the board will count one fault. After 5
faults, the board will lockout.
DETAILED DEFROST SYSTEM OPERATION
The demand defrost control board initiates a defrost cycle
based on either frost detection or time.
Frost Detection--If the compressor runs longer than 34
minutes and the actual difference between the clear coil
and frosted coil temperatures exceeds the maximum
difference allowed by the control, a defrost cycle will be
initiated.
IMPORTANT- The demand defrost control board will allow
a greater accumulation of frost and will initiate fewer
defrost cycles than a time/temperature defrost system.
Time--If six hours of heating mode compressor run time
has elapsed since the last defrost cycle while the coil
temperature remains below 35°F (2°C), the demand
defrost control will initiate a defrost cycle.
Actuation--When the reversing valve is de-energized,
the Y1 circuit is energized, and the coil temperature is
below 35°F (2°C), the board logs the compressor run time.
If the board is not calibrated, a defrost cycle will be initiated
after 34 minutes of heating mode compressor run time,
The control will attempt to self-calibrate after this (and all
other) defrost cycle(s),
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