Rheem 96MDV Series, Installation Instructions Manual

Page: 121 / 128

121
DIAGNOSTICS AND TROUBLESHOOTING
LOCKOUT AND REPLACING THE FURNACE CONTROL
All lockout conditions can be cleared immediately provided
that the original fault causing the lockout is cleared and
power to the unit is cycled off and then back on again or
(soft lockout only) if a heat call is cycled off for greater
than 2 seconds but less than 20 seconds.
The furnace control will not initiate a heat cycle during any
lockout condition. A call for compressor or continuous fan
will generally be responded to but control will display the
lockout error fault code instead of the “C” (for compressor)
or “F” (for Continuous fan).
FIVE-MINUTE LOCKOUT
A five minute “soft” lockout will be initiated if the low pres-
sure switch fails to close after 60 seconds of continuous
inducer operation at the beginning of a normal heat cycle
(pressure switch proving period). The seven-segment dis-
play will display the appropriate fault. Lockout will auto-
matically be reset after five minutes.
ONE-HOUR LOCKOUT
A one hour “soft” lock out will be initiated when:
Flame has not been detected after four igni- -
tion trials.
Flame has been lost for five times in one heat -
call.
Undesired flame has been detected. The one- -
hour period will commence after flame is no
longer detected.
Dead Blower has been detected (main limit -
circuit open for more than 150 seconds)
When voltage has unexpectedly been de- -
tected on the gas valve circuit and voltage
goes away when inducer is shut off.
If a Water Sensed condition is detected once -
during heat call (heat cycle terminated in re-
sponse to fault) and then clears and then is
detected again within 5 minutes of the next
heat attempt (same heat call).
The seven-segment display will alternately display “ 10 ”
and the code number for the fault causing the lockout.
Lockout will automatically be reset after one hour.
HARD LOCKOUT
Three conditions shall cause a hard lockout:
1. The control senses an unspecified internal fault. Fault
code “
93 ” is set and displayed. This lockout condition can-
not be reset by cycling the heat call.
2. Voltage is detected unexpectedly on the gas valve con-
tacts (welded relay) and will not clear by cycling
the inducer . Fault code “ 93 ” is set and displayed. This
lockout condition cannot be reset by cycling the heat call.
3. The furnace control will declare that the blower motor is
inoperable (dead) if the main limit control has been open
for more than 150 seconds. Gas heating is terminated.
However, the control continues to try to operate heating
for up to four attempts in case the blower motor starts
working again. If a dead blower has been declared four
times in one heat call, the furnace control enters a hard-
lockout. Fault code “
61 ” is set and displayed. This lockout
condition CAN be reset by cycling the heat call.
REPLACING THE FURNACE CONTROL
In the event that the furnace control must be replaced, the
memory card must be removed from the original furnace
control and retained with the furnace. A plastic tether with
a note wrapped around the tether is used to remind the
technician not to remove the card from the furnace. Use
this card to insert into the memory card connector labeled
P6 of the replacement control board. Failure to save and
connect the memory card properly to the replacement
control may result in no operation or undesired operation
of the furnace.
When replacing the furnace control, be sure to match the
dipswitch settings of the original control on the replace-
ment.
DO NOT CUT THE PLASTIC WIRE TIE USED AS A
TETHER TO THE ATTACHED MEMORY CARD. DOING
SO WILL DEFEAT THE PURPOSE OF RETAINING THE
MEMORY CARD – WHICH COULD LEAD TO A LOSS
OF CRITICAL DATA NECESSARY TO OPERATE THE
FURNACE. THE CARD MUST STAY WITH THE FUR-
NACE – EVEN WHEN THE FURNACE CONTROL (IFC)
MUST BE REPLACED. NEVER USE A CONTROL
BOARD TAKEN FROM ANOTHER FURNACE AS A RE-
PLACEMENT CONTROL FOR THIS FURNACE. FUR-
NACE CONTROLS TAKEN FROM OTHER FURNACES
MAY CONTAMINATE THE SYSTEM WITH THE WRONG
MODEL DATA WHICH CAN ONLY BE FIXED BY RE-
PLACING THE MEMORY CARD WITH THE ORIGINAL
MEMORY CARD FROM THE ORIGINAL FURNACE OR
A REPLACEMENT MEMORY CARD DESIGNED FOR
THE ORIGINAL FURNACE.
DIAGNOSING BLOWER MOTOR
ISSUES
If the main circulating blower motor will not operate when
it should, there are some different methods for diagnosing
the problem.
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