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START-UP PROCEDURES

This furnace is equipped with a direct
ignition device. Each time the room
thermostat calls for heat, the ignitor
lights the main burners directly. See the
lighting instructions on the furnace.

TO START THE FURNACE

1. Remove the burner compartment

control access door.

IMPORTANT:

Be sure that the

manual gas control has been in the
“OFF” position for at least five
minutes. Do not attempt to manually
light the main burners.

3. Turn off the furnace electrical power

and set the room thermostat to its
lowest setting.

4. Turn the gas control knob to the

“ON” position or move the gas
control lever to the “On” position.

5. Replace the burner compartment

control access door.

6. Turn on the furnace electrical power.
7. Set the room thermostat to a point

above room temperature to light the
main burners.

8. After the burners are lit, set the room

thermostat to a desired temperature.

TO SHUT DOWN

THE FURNACE

1. Set the room thermostat to its lowest

setting and wait for furnace to shut
down.

2. Remove the burner compartment

control access door.

3. Shut off the gas to the main burners

by turning the gas control knob to
the “OFF” position. See Figure 37.

SHOULD OVERHEATING OCCUR OR
THE GAS SUPPLY FAIL TO SHUT
OFF, CLOSE THE MANUAL GAS
VALVE FOR THE APPLIANCE
BEFORE SHUTTING OFF THE
ELECTRICAL SUPPLY. FAILURE TO
DO SO CAN CAUSE AN EXPLOSION
OR FIRE RESULTING IN PROPERTY
DAMAGE, PERSONAL INJURY OR
DEATH.

SEQUENCE OF OPERATION

UT ELECTRONIC CONTROLS &
INVESYS CLIMATE CONTROLS
Integrated Controls with Hot Surface
Ignition.

1. Each time the thermostat “W”

(Heating) contacts close, the
induced draft blower (inducer)
begins a prepurge cycle.

2. The air proving negative pressure

switch(es) closes.

5 seconds after the pressure
switch(es) close, the hot surface
igniter begins heating for 30
seconds

to full temperature. The

induced draft blower operates for the
complete heating cycle.

4. After the 30-second igniter warm up,

the gas valve opens for an
8-second trial for ignition.

5. The igniter lights the gas burners

and

stays energized for the first 7

seconds after the gas valve
opens.

6. 8 seconds after the gas valve opens

the remote flame sensor must
prove flame ignition for

one

second

using the process of flame

rectification. If the burners don’t light,
the system goes through another
ignition sequence. It does this

up to

four

times.

7. The main blower starts

approximately 20 seconds after the
burners ignite.

8. When the thermostat “W” (Heat Call)

ends, the gas valve closes, the
burners go out, the induced draft
blower stops after

a 10-second

post-purge,

and the negative

pressure switch(es) open.

9. The main blower continues until

timed off by the setting on the
integrated furnace control board.

Sequence if the system doesn’t light
or doesn’t sense flame:

1. On a call for heat, the control runs

the inducer for 35 seconds to
prepurge.

2. 5 seconds into prepurge, the hot

surface igniter heats for 30 seconds.
The inducer continues to run.

3. After the 30-second igniter warm up,

the gas valve opens for an
8-second trial for ignition. The
inducer continues and the igniter
stays energized.

4. If flame is not sensed during the 8th

second after the gas valve opens,
the gas valve closes, and the igniter
de-energizes.

5. After a 10-second post-purge, the

inducer stops and the control verifies
that the pressure switch has opened.
Once the open pressure switch is
confirmed, the control begins the
next ignition cycle by energizing the
inducer for a pre-purge of 30
seconds. After the 30-second pre-
purge, the igniter energizes and
begins a 30-second warm-up period
(inducer is still running). After a 30-
second igniter warm-up period (60
sec. of ind. running), the gas valve
opens and the control looks for a
flame signal for up to 8 seconds. If
no flame is sensed, the control goes
into “self-healing” mode, in which the
blower and inducer both run for three
minutes before another ignition
attempt is made.

NOTE: The following applies only
to units manufactured before third
Quarter 2003:

After 5-second inter-

purge, the control begins a 30-
second pre-purge followed by a 30-
second igniter warm-up period
(inducer is still running). After the 30-

second igniter warm-up period, the
gas valve opens and the control
looks for a flame signal for up to 8
seconds. If no flame is sensed, the
control goes into “self-healing”
mode, in which the blower and
inducer both run for three minutes
before another ignition attempt is
made.

6. The control attempts to ignite up to

four times (first attempt followed by
three retries). After the fourth
failure to ignite, the control goes
into a one-hour “soft-lockout,”
during which the control will not
respond to the thermostat heat call
(W). The lockout can be reset by
shutting off main power to the
furnace for five seconds, or by
turning the heat call (W) from the
thermostat off and then back on.
Note that second and fourth
ignition attempts will have a 30-
second pre-purge followed by a 30-
second igniter warm-up period.
This prevents the igniter from
overheating.

7. The above sequence will repeat

after a one hour delay. It will
continue repeating until ignition is
successful or the call for heat is
terminated.

To reset the lock out, make and
break power either at the
thermostat or at the unit
disconnect switch for 5 to 10
seconds.

It then goes through

another set of trials for ignition.

UT Electronic Controls Direct Spark
Ignition

1. Each time the thermostat contacts

close, the induced draft blower
(inducer) begins a prepurge cycle.

2. The air proving negative pressure

switch(es) closes.

30 seconds after the pressure
switch(es) close, the spark
igniter energizes.

The induced