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Electrical
ELECTROSTATIC DISCHARGE (ESD)
Precautions and Procedures
CAUTION
Electrostatic discharge can affect electronic
components.
neutralize electrostatic charge by touching
your hand and tools to metal prior to
handling the control.
NF96US unit components are shown in Figure 1. The
combustion air inducer, gas valve and burners can be
accessed by removing the outer access panel. The blower
and control box can be accessed by removing the blower
access panel.
Control Box Components (Figure 2)
Unit transformer (T1) and integrated ignition control
(A92) are located in the control box. In addition, a door
interlockswitch (S51) is located in the control box.
Transformer
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. The transformers on
all models are rated at 40VA with a 120V primary and 24V
secondary.
Door Interlock Switch (S51)
A door interlock switch rated 14A at 120VAC is located
on the control box. The switch is wired in series with line
voltage. When the blower door is removed the unit will shut
down.
Take
precautions
Door 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 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.
Integrated Ignition Control (A92)
to
Shock hazard.
Disconnect
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.
The hot surface ignition control system consisting of
an integrated control (Figure 3 with control terminal
designations in Table 1 through Table 3), sensor and
ignitor (Figure 5). The integrated control and ignitor work
in combination to ensure furnace ignition and ignitor
durability. The integrated control, controls all major furnace
operations. The integrated control also features a RED
LED for troubleshooting and two accessory terminals rated
at (1) one amp. See Table 4 for troubleshooting diagnostic
codes. The nitride ignitor is made from a non-porous, high
strength proprietary ceramic material that provides long life
and trouble free maintenance.
Pin #
1
2
3
4
Table 1. 4-Pin Terminal Designations
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
Table 2. 12-Pin Terminal Designations
Page 8
WARNING
power
before
Function
Combustion Air Inducer Line
Ignitor Line
Combustion Air Inducer Neutral
Ignitor Neutral
Function
High Limit Output
Not Used
24V Line
Not Used
Rollout Switch Out
24V Neutral
High Limit Input
Ground
Gas Valve Common
Pressure Switch In
Rollout Switch In
Gas Valve Out
servicing.
31-5000728 Rev. 0
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Troubleshooting
