Reznor UEAS Unit Installation Manual - Manual (Page 32)

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 pres-
ent (W energized). If the limit switch is open and a call for heat is present, the con-
trol de-energizes the gas valve and turns the fan/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 runs the blower/fan motor 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 sec-
onds), 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.
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 control will de-energize
the gas valve. If flame is lost before the end of the 2 second pressure switch rec-
ognition delay, the control will respond to the loss of flame. If the pressure switch
remains open for 2 seconds and the flame remains, the control de-energizes the
gas valve, the venter motor runs through post-purge, and the fan/blower motor
runs on heat speed through the selected fan off delay. When the fan off delay is
over, the fan/blower motor is de-energized, and a heat cycle is begun if the call for
heat still exists.
When the thermostat calls for continuous fan (G) without a call for heat, the fan
motor is energized after a .25 second delay. NOTE: This brief on delay is to allow
the “G” terminal to energize slightly before “Y” and an external changeover relay
to switch from “G” to “W” without causing momentary glitches in the fan/blower
output. The fan remains energized as long as the call for fan remains without a call
for heat.
If a call for heat (W) occurs during continuous fan, the fan/blower will de-energize.
A call for fan is ignored while in lockout.
Undesired Flame - If flame is sensed longer than 20 seconds while the gas valve
is de-energized, the control shall energize the venter motor and fan/blower motor
on heat speed. When flame is no longer sensed, the venter motor will run through
postpurge, and the fan/blower motor will run through the selected heat fan off
delay time. The control will do a soft lockout, but will still respond to open limit and
flame. The FLAME (yellow) LED shall flash rapidly when lockout is due to unde-
sired flame.
Gas Valve Relay Fault - If the control senses the gas valve as energized for more
than one second when the control 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 control will lockout with 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-
energized after the venter motor was shutoff for 15 seconds, then the venter motor
is re-energized to vent the unburned gas.
Soft Lockout - The control shall not initiate a call for heat or call for continuous
fan while in lockout. The control will still respond to an open limit and undesired
flame. Lockout shall automatically reset after one hour. Lockout may be manually
reset by removing power from the control for more than one second or removing
the thermostat call for heat for more than one and less than 20 seconds.
Continuous Fan
Operation
Fault Modes
Abnormal Heat Cycle
Functions (cont’d)
10.0 Ignition System
(cont’d)
Lockout
Form I-UEAS, Page 32