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START - UP
8. Set the thermostat at the desired temperature setting and the
unit wilt function automatically.
STARTING THE UNIT IN THE GAS HEATING MODE
1. Check to make sure all grilles and registers are open and all unit
access doors are closed before start-up.
2. Purge the gas supply line of air by opening the union ahead of
the unit. When the odor of gas is detected, retighten the union
and wait five (5) minutes before proceeding.
3. Set the walt thermostat to its lowest position and place the fan
switch in the AUTO or ON position.
4. Open the main gas valve(s) and turn on the unit power supply.
5. Reset the heating temperature lever on the room thermostat at
the highest value above room temperature.
The combustion
blower motor should energize. The main burners should light
within 20-25 seconds. Initial start may be delayed somewhat if
the unit has not been purged and air is trapped in the gas line.
NOTE: Blue smoke produced by the heat exchanger during the
initial burner firing is caused by a thin film of off on the surface
of the heat exchanger.
This off will burn off quickly.
6. Cycle the thermostat OFF and ON a few times at a rate of not
more than once every thirty (30) seconds.
Check both the
control operation and the burner operating conditions.
MANIFOLD PRESSURE
1,
2,
Connect a manometer to the pressure tap at the outlet side of
the unit's gas valve. Read the manifold pressure with the main
burners firing.
If the manifold pressure reading does not match the value
indicated on the unit nameplate,
the unit pressure regulator
must be adjusted as follows:
a. Remove the cover screw on the gas regulator located on the
front side of the unit's gas valve.
b. Turn the adjusting screw clockwise
to increase manifold
pressure or counterclockwise
to decrease manifold pres-
sure.
3. Check the temperature rise during furnace operation to insure
that it falls within the range specified on the unit nameplate.
4. If the temperature rise noted is outside of the specified limits,
adjust the indoor air flow to cause the temperature
rise d the
heat exchanger to fall within the required range.
SEQUENCE
OF OPERATION
Operation of the unit heating or cooling cycles is controlled by the
setting of the system switch on the room thermostat.
Once the
system switch is placed either in the "HEAT" or "COOL" position, unit
operation is automatic. Afan switch on the thermostat also provides
for it continuous operation of the evaporator fan when desired. The
fan switch "ON" position provides continuous operation while the
"AUTO" position provides operation during the heating or cooling
cycles.
HEATING CYCLE
Thermostat
call for heat ( 2-stage thermostat)
Call for 1st stage only:
(R) and (W1) thermostat contacts close signaling the control module
(IGN) to run its self-check routine. After the control has verified that
the pressure switch (PS) contacts are open, the limit switch (TCO)
contacts are closed, and the flame rollout (FL) switch is closed, the
induced draft blower (CBM) will be energized on high speed for
approximately
15 seconds.
After the induced draft blower (CBM) has come up to speed, the
control will verify that the pressure switch (PS) contacts are closed
and switch the induced draft blower to low speed for an additional
5 seconds of prepurge. The gas valve (GV) is energized in the first
stage to permit gas flow and the spark ignitor (IP) is energized. The
flame detector (FD) confirms that ignition has been achieved within
the 7 second trial period.
As the flame detector confirms that ignition has been achieved the
delay to indoor fan on period begins timing and after approximately
45 seconds, the indoor blower motor (IDM) will be energized at low
speed and will continue to run during the heating cycle.
Call for 2nd stage after 1st stage:
(R) and (W2) thermostat contacts close signaling a call for second
stage heat. The induced draft motor (CBM) is energized on high
speed and the gas valve on second stage. After approximately
30
seconds the control energizes the indoor blower on high speed.
2rid stage satisfied,
1st stage still called:
(R) and (W2) opens, the induced draft blower is reduced to low
speed the gas valve is reduced to first stage. After aprox. 30
seconds the indoor blower motor is reduced to low speed.
1st stage satisfied:
(R) and (Wl) opens, the gas valve (GV) will close. The induced draft
blower (CBM) will be de-energized
after approximately
5 seconds
postpurge. The indoor btower motor (IDM)witt continue to run for the
fan off period (field setectabte 60 or 90 seconds [by jumpers]), then
wilt be de-energized by the control module.
Thermostat
satisfied:
(R) and (W1/W2) (jumpered) contacts open signaling the control
module to close the gas valve and de-energize
the induced draft
blower after approximately
5 second postpurge. The I.D. blower
motor will continue to operate at the current speed for 60 or 90
seconds after the flames are extinguished.
SAFETY SEQUENCES
This product is equipped with safety devices to protect against
abnormal conditions.
The temperature
limit switch (TCO) is located in the gas com-
partment on the vestibule panel above the burner assembly. This
automatic reset device protects against excessive leaving air tem-
perature. If this device opens, the gas valve is immediately closed
and will not permit operation until the limit switch closes.
Page 19
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