508187-01
Issue 2116
Page 13 of 51
Unit Components
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
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
A80UH2E / 80G2UHE(L) 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.
A80UH2E / 80G2UHE(L) 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.
Control Box Components (Figure 2)
Transformer
Integrated Control
Interlock Switch
Circuit Breaker
Figure 2. Control Box
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.
Door Interlock Switch (S51)
A door interlock switch is wired in series with line voltage.
When the inner blower access panel is removed the unit
will shut down.
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 at 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.
Figure 3. Circuit Breaker (CB8)
PRESS TO RESET
Integrated Ignition Control (A92)
Shock hazard.
Disconnect power before servicing.
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
Units are equipped with a two-stage, integrated control.
The system consists of a ignition / blower control (Figure
4 and Figure 5) with control pin designations in Table 1
and Table 2 and 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 and error codes.
The LED flashes in single digits. For example, using Table
4 under LIMIT CODE, an “E” followed by “2” followed by “5”
followed by “0”, the limit switch circuit is open. The control
also has two unpowered (dry) 1/4” contacts for a humidifier
and a 120 volt accessory terminal. Both rated at (1) one
amp each.
