If there are questions regarding the heat exchanger orientation, contact the Johnson
Controls Field Service Support staff for further information and directions.
Additional Safety Controls – These controls are included for reference but considered to be well covered
in the Installation Manuals.
C.
CONTROL CIRCUIT FUSE
- A 3-amp fuse is provided on the control circuit board to protect the
24-volt transformer from overload caused by control circuit wiring errors. This is an ATO 3,
automotive type fuse and is located on the control board. Corrective Action is required.
Recommended steps are to:
a. Supply voltage field wiring to the unit must have a ground connection. Verify ground wires
and conductor connectors are tight and secure.
b. Verify electrical continuity on service conductors and circuits.
c. Confirm no low voltage wiring or components are shorted to ground.
D.
ELECTRICAL INTERLOCK SWITCH / BLOWER DOOR SAFETY SWITCH
- This unit is
equipped with an electrical interlock switch mounted in the burner compartment. 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.
E.
PRESSURE SWITCH
- This furnace is equipped with a pressure sensor in the burner
compartment near the combustion blower. This sensor monitors combustion airflow through
furnace and piping systems. If any of the conditions listed below are detected by the pressure
sensor, the control board will prevent a hazardous condition from occurring by (depending on
furnace model) shutting off the gas valve or speeding up the combustion blower motor (some
models) to maintain adequate combustion airflow. If the combustion blower is already operating
at full speed, the furnace control will then start reducing (some models) the input to the furnace to
maintain proper combustion with the amount of combustion airflow available. The sensor will
detect the following conditions:
a. Blockage of vent piping or vent terminal,
b. Failure of combustion air blower motor or combustion air blower wheel.
If there are any questions or comments regarding these safety sensors and controls, please contact the
Johnson Controls Field Service Support staff for further information and directions.
Warm regards,
Casey McConnaughy
Ducted Systems Technical Support Engineer II
Residential Distributor Support
Ducted Systems Technical Support – Johnson Controls
