CSA 96MDT SERIES, Installation Instructions Manual

Page: 87 / 100

87
START-UP PROCEDURE
SEQUENCE OF OPERATIONS
Start- Up
This furnace is equipped with a direct ignition control. 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.
2. 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 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 tem-
perature to light the main burners. The heat call
should be adequate to activate the high stage gas
heat – generally, the thermostat setpoint should be
more than 2°F above room temperature. Consult your
thermostat specs to be sure.
8. Operate high gas heat for a minimum period of 15
minutes and adjust input rate (page 88) and observe
condensate system for leaks. Correct leaks and set
rate, shutdown furnace and repeat until no leaks in
condensate system can be detected.
9. Once high heat operation has been successfully veri-
fied and rate adjusted, the thermostat should be ad-
justed to set the heat call to low stage. This is
generally with the heating setpoint at about 1°F above
room temperature. Consult your thermostat specs to
be sure.
10. Operate low gas heat for a minimum period of 15 min-
utes and adjust input rate (page 88) and observe con-
densate system for leaks. Correct leaks and set rate,
shutdown furnace and repeat until no leaks in conden-
sate system can be detected.
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 to the “OFF” position.
SEQUENCE OF OPERATION
UT ELECTRONIC CONTROLS
Integrated Controls with Direct Spark Ignition.
UT ELECTRONIC CONTROLS Integrated Controls
with Direct Spark Ignition.
1. Each time the thermostat “W” (Heating) contacts
close, the furnace control checks to make sure that
both pressure switches are open. This is true of a low
or high heat call as “W” is energized on either call.
Next the induced draft blower (inducer) begins a pre-
purge cycle at high stage.
2. The air proving negative pressure switches (both low
and high) close.
3. After the 30-second pre-purge, the gas valve opens
on high stage for an 8-second trial for ignition.
4. The spark igniter is energized to light the gas burners
and stays energized for the up to 7 seconds after
the gas valve opens.
5. 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 before
entering a 1-hour lockout.
6. 20 seconds after flame is sensed, the gas valve is set
to the thermostat demand (low or high) (note if thermo-
stat demand is high, the gas valve is already at high
stage and will not switch) and the main blower will be
energized at either the low or high gas heat stage de-
pending on the thermostat demand.
7. When the thermostat “W” (Heat Call) ends, the gas
valve closes, flame is extinguished, the induced draft
blower stops after
a 10-second post-purge, and the
negative pressure switch opens.
8. The main blower continues until timed off by the set-
ting on the integrated furnace control board.
Sequence if the system doesn’t light or doesn’t sense
flame:
1. Each time the thermostat “W” (Heating) contacts
close, the furnace control checks to make sure that
both pressure switches are open. This is true of a low
or high heat call as “W” is energized on either call.
Next the induced draft blower (inducer) begins a pre-
purge cycle at high stage.
2. After the 30-second pre-purge, the gas valve opens
on high stage for an 8-second trial for ignition.
!
WARNING
SHOULD OVERHEATING OCCUR OR THE GAS SUP-
PLY 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.