508183-01
Issue 2114
Page 6 of 52
Unit Components
GUH96T
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 section.
Electrostatic discharge can affect
electronic
components.
Take
precautions to neutralize electrostatic
charge by touching your hand and
tools to metal prior to handling the
control.
CAUTION
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.
Integrated Control
Door Interlock Switch
Transformer
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.
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.
WARNING
Integrated Control (A92)
Units are equipped with a variable capacity integrated
control. The system consists of an ignition / blower
control (Figure 3) with control pin designations (Table 3
and Table 4) 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 furnace has a built-in, self-diagnostic capability. If a
system problem occurs, a fault code is shown by a red
LED on the control. The control continuously monitors its
own operation and the operation of the system. If a failure
occurs, the LED will indicate the failure code. The flash
codes are presented in Table 2.
Fault Code History Button
The control stores the last five fault codes in memory. A
pushbutton switch is located on the control. When the
pushbutton switch is pressed and released, the control
flashes the stored fault codes. The most recent fault code
is flashed first; the oldest fault code is flashed last. To clear
the fault code history, press and hold the pushbutton switch
in for more than 5 seconds before releasing.
Single Stage Thermostat Operation
The automatic heat staging option allows a single stage
thermostat to be used with two stage furnace models. To
activate this option, move the jumper pin (see Figure 3) to
desired setting (5 minutes or 10 minutes). The furnace will
start on 1st stage heat and stay at 1st stage heat for the
duration of the selected time before switching to 2nd stage
heat.
W1 on the integrated control must be connected to W1 on
the thermostat.
High Heat State LED
A green LED is provided on the control board to indicate
