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Unit Components
GUH97M unit components are shown in Figure 1.
The gas valve, combustion air inducer and burners
can be accessed by removing the access panel.
Electrical components are in the control box (Figure
2) found in the blower compartment. GUH97M units
are factory-equipped with a bottom return air panel in
place. The panel is designed to be field removed as
required for bottom air return. Markings are provided for
side return air and may be cut out in the field.
Electrostatic
electronic
precautions to neutralize electrostatic
charge by touching your hand and
tools to metal prior to handling the
control.
Control Box
Control Transformer (T1)
A transformer located in the control box provides power
to the low voltage section of the unit. Transformers on all
models are rated 40VA with a 120V primary and a 24V
secondary.
Transformer
Circuit Breaker
Figure 2. Control Box
Door Interlock Switch (S51)
A door interlock switch rated 14A at 125VAC is wired in
series with line voltage. When the inner blower access
panel is removed the unit will shut down.
Page 8 of 70
CAUTION
discharge
can
components.
Interlock Switch
Integrated Control
Circuit Breaker (CB8)
A 24V circuit breaker is also located in the control box. The
switch provides overcurrent protection to the transformer
(T1). The breaker is rated 3A at 32V. If the current exceeds
this limit the breaker will trip and all unit operation will
shutdown. The breaker can be manually reset by pressing
the button on the face. See Figure 3.
PRESS TO RESET
affect
Take
Shock hazard.
Disconnect power before servicing. Integrated control
is not field repairable. If control is inoperable, simply
replace entire control.
Can cause injury or death. Unsafe operation will result
if repair is attempted.
Integrated Control (A92)
The control can operate with a non-communicating
conventional single or two-stage thermostat. The system
consists of an ignition / blower control (Figure 4 and
Figure 5) with control pin designations (Table 1 through
Table 2) and an ignitor. The control and ignitor work in
combination to ensure furnace ignition and ignitor
durability. The control provides gas ignition, safety checks
and indoor blower control with two-stage gas heating. The
furnace combustion air inducer, gas valve and indoor
blower are controlled in response to various system inputs
such as thermostat signal, pressure and limit switch signal
and flame signal. The control features a seven-segment
LED display, indicating furnace status (including indoor
blower) and error codes. The LED flashes in single digits.
For example, using Table 13 under CODE, an "E" followed
by "2" followed by "5" followed by "0", the limit switch
circuit is open. The control has a 120V humidifier and a
120V accessory terminal, both rated at (1) one amp each.
Issue 2051
Figure 3. Circuit Breaker CB8
WARNING
508146-01
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