Form I-UDA, P/N 195673 Rev 13, Page 5
4) Fan/Blower On Delay
- The control waits for 30 seconds from the time the gas
valve opened and then energizes the fan/blower motor. The gas valve and venter
motor remain energized. The control proceeds to steady heat mode.
5) Steady Heat
- Control inputs are continuously monitored to ensure limit and pres
-
sure switches are closed, flame is established, and the thermostat call for heat remains.
When the thermostat call for heat is removed, the control de-energizes the gas valve
and begins post-purge and fan/blower off delay timing.
6) Post Purge
- The venter motor output remains on for a 45-second post-purge period
after the thermostat is satisfied.
7) Fan/Blower Off Delay
- The fan/blower motor is de-energized after a fan/blower off
delay as selected by the dip switches. Timing begins when the thermostat is satisfied.
Delay times are as follows:
SW1 SW Time
OFF OFF 120 seconds (default when shipped)
OFF ON
90 seconds
ON
OFF 160 seconds
ON
ON
45 seconds
Interrupted Thermostat Call for Heat
- If the thermostat demand for heat is removed
before the flame is recognized, the control will run the venter motor for the post purge
period and de-energize all outputs.
If the thermostat demand for heat is removed after successful ignition, the control will
de-energize the gas valve, run the venter motor through post purge, and run the fan/
blower motor on heat speed for the selected delay off time.
Ignition Retry
- If flame is not established on the first trial for ignition period, the control
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 control
initiates another trial for ignition.
If flame is not established on the second trial for ignition, the control de-energizes the
gas valve, energizes the fan/blower motor on heat speed, and venter motor remains
energized. The fan/blower motor is shut off after the longest selectable fan delay time
(160 seconds). When the fan/blower motor de-energizes, the spark and gas valve are
re-energized and the control initiates another trial for ignition. (This fan delay is self-
healing feature for an open auxiliary limit switch).
If flame is not established on the third trial for ignition period, the control de-energizes
the gas valve, and the venter motor remains energized for an inter-purge period of 10
seconds. The control then re-energizes the gas valve and spark and initiates another
trial for ignition.
If flame is not established on the fourth trial for ignition (initial try plus 3 re-tries), the
control de-energizes the gas valve and goes into lockout. The control 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 turns the fan/blower motor on heat speed 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 and runs the blower/fan motor through the selected fan off delay.
The control will return to normal operation after fan off delay is completed.
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 control will re-start the heat cycle at the pressure switch proving state if the
call for heat still exists.
Abnormal Heat Cycle
Functions
