
035-17468-001 Rev. A (801)
24
Unitary Products Group
SAFETY CONTROLS
Control Circuit Fuse:
A 3 amp. fuse is provided to protect
the 24 volt transformer from overload caused by control cir-
cuit wiring errors. This is an ATO 3, automotive type fuse and
is located in the unit wiring harness between the control
transformer and the furnace control.
Blower Door Safety Switch:
This unit is equipped with an
Electrical Interlock Switch mounted in the blower compart-
ment. This switch interrupts all power at the unit when the
panel covering the blower compartment is removed.
Electrical supply to this unit is dependent upon the panel that
covers the blower compartment being in place and properly
positioned.
Rollout Switch Controls:
This control is mounted on the
burner box assembly. If the temperature in the burner com-
partment exceeds its set point, the igniter control and the gas
valve are de-energized. The operation of this control indi-
cates a malfunction in the combustion air blower, heat
exchanger or a blocked vent pipe connection. Corrective
action is required. This is a manual reset control and must be
reset before operation can continue.
Pressure Switches:
This furnace is supplied with pressure
switches which monitor the flow through the combustion air/
vent piping system. These switches de-energize the ignition
control module and the gas valve if any of the following condi-
tions are present.
1.
Blockage of combustion air piping or terminal:
• Low fire (1LP)
• High fire (2 LP)
2.
Blockage of vent piping or terminal:
• Low fire (1LP)
• High fire (2 LP)
3.
Failure of combustion air blower motor:
• Low fire (1LP)
• High fire (2 LP)
4.
Blockage of condensate drain piping:
• Low fire (1LP)
• High fire (2 LP)
5.
Blockage of condensate drain piping (horizontal right
installations only).
• Low fire (3 LP)
• High fire (3 LP)
FIGURE 35 :
Horizontal Application Condensate Drain Connection
RIGHT AIRFLOW
(INDUCER HIGH)
LEFT AIRFLOW
(INDUCER HIGH)
1. CONDENSATE PAN TO TRAP “A” DIMENSIONS.
2. INDUCER BOTTOM TO TRAP “B” DIMENSIONS.
3. INDUCER OUTLET TO TRAP “C” DIMENSIONS.
1. INDUCER OUTLET TO TRAP USE AS PROVIDED.
5. CONDENSATE PAN TO TRAP “D” DIMENSIONS.
3
1
2
A
D
5
4
B
C
HOSE IDENTIFIER NUMBERS:
HOSE IDENTIFIER NUMBERS:
Blower and burner must never be operated without
the blower panel in place.
Main power to the unit must still be interrupted at the
main power disconnect switch before any service or
repair work is to be done to the unit.
Do not rely
upon the interlock switch as a main power
disconnect.