Reznor MAPS III, Cabinet D RECB Users Manual User Manual
Page 29
Form O-MAPSIII Cabinet D, P/N 222918R9, Page 29
Ignition System
Fault Modes - Non-
Modulating Furnace
of D Cabinet with Size
1000, 1200, 1400, or
1600 Heat Section
If flame is not established on the 4th trial for ignition (initial try plus 3 re-tries), the circuit
board de-energizes the gas valve and goes into lockout. The circuit board goes to one
flash on the green LED to indicate ignition failure lockout.
Limit Switch Operation - The limit switch is ignored unless a call for heat is present
(W energized). If the limit switch is open and a call for heat is present, the control de-
energizes the gas valve and runs the blower motor on heat speed and runs the venter
motor. The control will be in soft lockout and flashing fault code "3" before returning to
normal operation.
When the switch re-closes or the call for heat is lost, the control runs the venter motor
through post purge and the blower through the selected fan off delay.
Pressure Switch - If the pressure switch opens before the trial for ignition period, the
venter motor will run through the pressure switch recognition delay (2 seconds), the
gas valve will be de-energized, and the venter motor will run through the postpurge
time. The ignition system circuit board will re-start the heat cycle at the pressure switch
proving state if the call for heat still exists.
Pressure switch opening for less than 2 seconds during the trial for ignition period shall
not interrupt the heat cycle. (Gas valve will de-energize while the pressure switch is
open.)
If the pressure switch opens after a successful ignition, the circuit board will de-ener-
gize the gas valve. If flame is lost before the end of the 2 second pressure switch rec-
ognition delay, the circuit board will respond to the loss of flame. If the pressure switch
remains open for 2 seconds and the flame remains, the circuit board de-energizes the
gas valve and the venter motor runs through postpurge
Undesired Flame - If flame is sensed longer than 20 seconds while the gas valve
is de-energized, the circuit board shall energize the venter motor. When flame is no
longer sensed, the venter motor will run through postpurge. The circuit board will do
a soft lockout, but will still respond to open limit and flame. The FLAME (yellow) LED
flashes rapidly.
Gas Valve Relay Fault - If the circuit board senses the gas valve as energized for
more than one second when the circuit board is not attempting to energize the gas
valve, or the gas valve is sensed as not energized when it is supposed to be energized,
then the circuit board will lockout with the green LED off. The control assumes either
the contacts of the relay driving the gas valve have welded shut, or the sensing circuit
has failed. The venter motor is forced off to open the pressure switch to stop gas flow
unless flame is present.
If the gas valve was sensed as closed when it should be open, and has not de-ener-
gized after the venter motor was shutoff for 15 seconds, then the venter motor is re-
energized to vent the unburned gas.
Soft Lockout - The circuit board shall not initiate a call for heat while in lockout. The
circuit board will still respond to an open limit and undesired flame. Lockout shall auto-
matically reset after one hour. Lockout may be manually reset by removing power from
the circuit board for more than one second or removing the call for heat for more than
one and less than 20 seconds.
Hard Lockout - If the circuit board detects a fault on the board, the status LED will
be de-energized, and the circuit board will lockout as long as the fault remains. A hard
lockout will automatically reset if the hardware fault clears.
Power Interruption - During a momentary power interruption or at voltage levels
below the minimum operating voltage (line voltage or low voltage) the ignition system
will self-recover without lockout when voltage returns to the operating range.
Power interruptions of less than 80mS shall not cause the circuit board to change
operating states. Power interruptions greater than 80mS may cause the circuit board
to interrupt the current operating cycle and re-start.