Form I-XE/CRGB/RPB, Page 30
Operating Sequence for Gravity-Vented Models
1. Set the thermostat switch at its lowest setting.
2. Turn on power, main and pilot manual gas valves.
3. Set thermostat at desired setting.
4. On call for heat by the thermostat, the pilot gas valve and spark
gap are energized to produce a pilot flame on each operating
cycle. The sensing probe proves the presence of the pilot flame
and energizes the safety switch portion of the control. The
switch action de-energizes the spark gap and energizes the main
valve. The main gas ignites and the unit fires at full rate. NOTE:
If the flame is extinguished during main burner operation, the
safety switch closes the main valve and recycles the spark gap.
On unit equipped with a G770NGC-4 controller which includes
lockout, if the pilot is not established within 120 seconds
(approximately), the unit locks out and must be reset by
interrupting the power to the control circuit (See Lighting
Instructions).
5. Blower motor operates from fan time delay.
6. Set the thermostat switch at lowest setting for shutdown.
Blower motor remains on as determined by fan time delay.
Operating Sequence - Power-Vented Models
1. Set the thermostat switch at its lowest setting.
2. Turn on power, main and manual gas valves.
(a) Firing rate is controlled by the thermostat.
(b) Blower motor operates from time delay relay.
3. Set thermostat switch at desired setting.
4. Thermostat calls for heat
(a) The venter motor is energized after 15-second (approximate)
time delay.
(b) Venter flow switches from N.C. to N. O. contacts, energizing
the pilot gas valve and spark gap to produce a pilot flame on
each operating cycle. The sensing probe proves the presence
of the pilot flame and energizes the safety switch portion of
the control. The switch action de-energizes the spark gap and
energizes the main valve. The main gas ignites and the unit
fires at full rate.
5. If the flame is extinguished during main burner operation, the
safety switch closes the main valve and recycles the spark gap.
On unit equipped with a G770NGC-4 controller which includes
30. Check Installation and Start-Up
Check the installation prior to start-up:
Be certain the electrical supply matches voltage rating of the
furnace. (Refer to the rating plate.)
Check all field wiring against the wiring diagram. Be sure that
wire gauges are as required for the electrical load.
Be certain that the electrical entrances are sealed against the
weather.
Check that fuses or circuit breakers are in place and sized
correctly.
Be sure that all condensate drains are open. See Paragraph 9.
Be certain that all optional manual reset controls (firestat and
high gas pressure switch) are reset.
Check clearances from combustibles. Requirements are shown
in Paragraph 5.
Check piping for leaks and proper gas line pressure. Bleed gas
lines of trapped air. See Paragraph 11.
a) Turn manual shutoff valve to off position.
b) Turn gas supply on.
c) Observe gas meter for movement, or
28. Burner and Carryovers (cont'd)
INDOOR Gravity-Vented Furnace (Models XE/HXE) - Natural gas
burners are equipped with two flash carryover systems that receive a
supply of gas simultaneously with the main burner. (NOTE: A natural
gas burner rack on indoor furnaces manufactured prior to 3/95 has a gas
lighter tube carryover and one flash carryover.)
Propane
gas
burners are
equipped with one flash carryover and a regulated gas lighter tube sys-
tem.
OUTDOOR Gravity-Vented Furnace (Model Series CRGB ) - Natu-
ral gas
burners are equipped with a gas lighter tube carryover on the
orifice end of the burner rack and a flash carryover on the other end.
Propane gas
burners are equipped with one flash carryover and a regu-
lated gas lighter tube system.
OUTDOOR Power-Vented Furnace (Model Series RPB) - Natural
gas
burners are equipped with a gas lighter tube carryover on the orifice
end of the burner rack and a flash carryover on the other end.
Propane
gas
burners are equipped with one flash carryover and a regulated gas
lighter tube system.
During regular service, check the main burner ports, the carryover as-
semblies, and the orifices for cleanliness.
29. Burner Air Adjustment
Burner air shutters are not normally required on natural gas furnaces. Air
shutters are required on propane gas units and may require adjustment.
Before making any adjustment to the air shutters, allow the furnace to
operate for about fifteen minutes with the air shutters open. The slotted
screw on the end manifold bracket moves the air shutters and adjusts all
burners simultaneously. Turning the screw clockwise opens the shut-
ters; counterclockwise closes the shutters. After the furnace has been in
operation for 15 minutes, close the air shutters observing the flame for
yellow-tipping. Open the shutters until the yellow disappears. A lim-
ited amount of yellow-tipping is permissible for liquefied petroleum
gases. Natural gas should not display any yellow-tipping.
When making the adjustment, close the air shutters no more than is
necessary to eliminate the problem condition.
DANGER: Failure to install and/or adjust air
shutters according to directions could cause
property damage, personal injury, and or death.
d) Attach pressure gauge readable to .1" w.c. and after turning gas
on for ten seconds, turn gas supply off. No change in pressure
should occur over a three-minute period.
e) If either c) or d) above indicate a leak, locate leak by brushing
a soapy solution on all fittings. Bubbles will appear at a leak.
Repair and repeat tests.
Power Vented Models - Check to make sure that flue dis-
charge and combustion air inlet openings are free from ob-
structions.
Gravity Vented Models - Be sure that vent cap is installed
properly. If required, vent cap extension must be installed. See
Paragraph 8B.
Check blower pulley and motor pulley to be sure they are
secure to the shafts. Check belt tension and alignment. See
Paragraph 13.
If the furnace is equipped with outside air and return air damp-
ers, adjust the damper linkage. See Paragraph 34.
Start-Up
Turn electric and gas supply on to the furnace. Adjust the
thermostat or ductstat so that a call for heat exists. Observe
for complete sequencing of safety pilot and ignition.
