Reznor MAPS II Unit Installation Manual - Manual (Page 47)

Form I-MAPS II, P/N 206131 (Rev 13), Page 47
Abnormal Heat Cycle
Functions
Interrupted Call for Heat - If the system controller call for heat is removed
before the flame is recognized, the circuit board will run the venter motor for
the post purge period and de-energize all outputs.
If the call for heat is removed after successful ignition, the circuit board will de-
energize the gas valve and run the venter motor through post purge.
Ignition Retry - If flame is not established on the 1st trial for ignition period, the
ignition system circuit board de-energizes the gas valve, and the venter motor
remains energized for an inter-purge period of 10 seconds. The spark and gas
valve are then re-energized, and the circuit board initiates a 2nd trial for igni-
tion.
If flame is not established on the 2nd trial for ignition, the circuit board de-ener-
gizes the gas valve and venter motor remains energized. The spark and gas
valve are re-energized and the circuit board initiates a 3rd trial for ignition.
If flame is not established on the 3rd trial for ignition period, the circuit board
de-energizes the gas valve, and the venter motor remains energized for an
inter-purge period of 10 seconds. The circuit board then re-energizes the gas
valve and spark and initiates a 4th trial for ignition.
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. If the limit switch is open and a call for heat is present, the control de-
energizes the gas valve and runs the venter motor.
When the switch re-closes or the call for heat is lost, the control runs the venter
motor through post purge. The control will return to normal operation.
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-energize the gas valve. If flame is lost before the end of the 2 second pres-
The ignition system circuit board runs the venter motor for a 20 second pre-
purge time, then proceeds to the ignition trial period.
3) Ignition Trial Period - The ignition system circuit board energizes the spark
and main gas valve. The venter remains energized. If flame is sensed at the
1/3 burner section during the first 16 seconds, the spark is de-energized. If
flame has not been sensed during the first 16 seconds, the control de-ener-
gizes the spark output and keeps the gas valve energized for an additional one
second flame proving period. If flame is not present after the flame proving
period, the control de-energizes the gas valve and proceeds with ignition re-
tries as specified in “Abnormal Heat Cycle, Ignition Retry”. If flame is present,
the circuit board proceeds to steady heat..
4) Steady Heat - Circuit board inputs are continuously monitored to ensure
limit and pressure switches are closed, flame is established (sensor on both
burner sections), and the system controller call for heat remains. When the
call for heat is removed, the ignition system circuit board de-energizes the gas
valve and begins postpurge timing.
5) Post Purge - The venter motor output remains on for a 45 second postpurge
period after the system controller is satisfied.