Daikin APGM3 Service And Troubleshooting page 52

TROUBLESHOOTING
Open Thermal Protection Device
If the primary limit switch opens, the gas valve is
immediately de-energized, the induced draft and air
circulating blowers are energized. The induced draft and
air circulator blowers remain energized until the limit switch
recloses. The diagnostic fault code for an open limit is four
(4) flashes.
A primary limit will open due to excessive supply air
temperatures. This can be caused by a dirty filter,
excessive duct static, insufficient air flow, or a faulty limit.
Check filters, total external duct static, blower motor, blower
motor speed tap (see wiring diagram), and limit. This limit
will automatically reset once the temperature falls below a
preset level.
Primary Limit
A primary limit will open due to excessive supply air
temperatures. This can be caused by a dirty filter,
excessive duct static, insufficient air flow, or a faulty limit.
Check filters, total external duct static, blower motor, blower
motor speed tap (see wiring diagram), and limit. This limit
will automatically reset once the temperature falls below a
preset level.
Auxiliary/Secondary Limit
A dirty filter, excessive duct static, insufficient air flow, a
faulty limit, or a failed circulator blower can cause this limit
to open. Check filters, total external duct static, circulator
blower motor, blower motor speed tap (see wiring diagram),
and limit. An interruption in electrical power during a
heating cycle may also cause the auxiliary limit to open.
The automatic reset secondary limit is located on top of the
circulator blower assembly.
Rollout Limit
If the burner flames are not properly drawn into the heat
exchanger, the flame rollout protection device will open.
Possible causes are restricted or blocked flue passages,
blocked or cracked heat exchanger, a failed induced draft
blower, or insufficient combustion air. The rollout protection
device is a manual reset limit located on the burner
bracket. The cause of the flame rollout must be determined
and corrected before resetting the limit.
Flame Detected with Gas Valve Closed
If flame is detected with the gas valve de-energized, the
combustion and air circulator blowers are energized. The
diagnostic fault code is five (5) flashes for this condition.
The control can be reset by removing the power supply
to the unit or it will automatically reset after one hour.
Miswiring is the probable cause for this fault.
Low Flame Signal (Two-Stage Models ONLY)
Under some conditions, the fuel or air supply can create a
nearly invisible coating on the flame sensor. This coating
acts as an insulator causing a drop in the flame signal. If
the flame signal drops below a predetermined value, the
ignition control will display an error code of (1) flash on the
amber diagnostic LED. The unit will continue to operate
until the control can no longer detect flame.
Abnormal Operation - Cooling
Short Cycle Compressor Delay
The automatic ignition control has a built-in feature that
prevents damage to the compressor in short cycling
situations. In the event of intermittent power losses or
intermittent thermostat operation, the ignition control will
delay output to the compressor contactor for three minutes
from the time power is restored. (Compressor is off a total
of three minutes). The diagnostic LED will flash six (6)
times to indicate the compressor contactor output is being
delayed.
NOTE: Some electronic thermostats also have a built-
in compressor short cycle timer that may be longer
than the three minute delay given above. If you are
using an electronic thermostat and the compressor
has not started after three minutes, wait an additional
five minutes to allow the thermostat to complete its
short cycle delay time.
High Pressure Switch/Low Pressure Switch
(5-Ton Models ONLY)
Some models include a high pressure cutout switch and/
or a loss of charge cutout switch. The high pressure cutout
switch protects the refrigeration system from excessive
operating pressures. The loss of charge cutout switch
protects the refrigeration system from very low operating
pressures due to a loss of refrigerant. Compressor
operation will be disabled if either of these devices opens.
If either device opens, the diagnostic red LED will flash (9)
times to indicate that a refrigeration system pressure switch
is open.
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