508096-01
Issue 2037
Page
10
of 3
1
Figure 6. Heating Components
Gaskets
Collector Box
Orifice Plate
Flue Transition
Pressure Switch
Combustion Air Inducer
Manifold And Gas Valve
Ignitor
Sensor
Rollout Switches
Cooling Fan On Time
The fan on time is 2 seconds and is not adjustable.
Cooling Fan Off Time
The control has a 45 second fan off delay after cooling
demand has been met. This delay is factory set and not
adjustable.
GUH80C
units use a nitride ignitor made from a
proprietary ceramic material. To check ignitor, measure
its resistance and voltage. A value of 39 to 70
ohms indicates a good ignitor. Voltage to the ignitor
should be 102 - 132VAC. See Figure 9 for resistance
and voltage checks.
NOTE:
The
GUH80C
furnace contains electronic
components that are polarity sensitive. Make sure that
the furnace is wired correctly and is properly
grounded.
Flame Rollout Switches (Figure 6)
Flame rollout switch (S47) is a high temperature limit. Each
furnace is equipped with two identical switches. The limit
is a N.C. SPST manual-reset limit connected in series
with the integrated control A92. When S47 senses rollout,
the integrated control immediately stops ignition and
closes the gas valve. If unit is running and flame rollout is
detected, the gas valve will close and integrated control
will be disabled. Rollout can be caused by a blocked
heat exchanger, blocked flue or lack of combustion air.
The switch has a factory setpoint of 210°F and cannot
be adjusted. To manually reset a tripped switch, push the
reset button located on the control.
A flame sensor is located on the left side of the burner
support. The sensor is mounted on the flame rollout plate
and the tip protrudes into the flame envelope of the left-
most burner. The sensor can be removed for service (clean
with steel wool) without removing any part of the burners.
During operation, flame is sensed by current passed
through the flame and sensing electrode. The integrated
control allows the gas valve to remain open as long as
flame signal is sensed.
