41
discharge. This procedure is applicable to both installed and
uninstalled (ungrounded) furnaces.
1. Disconnect all power to the furnace. Do not touch the
integrated control module or any wire connected to the
control prior to discharging your body’s electrostatic
charge to ground.
2. Firmly touch a clean, unpainted, metal surface of the
furnace away from the control. Any tools held in a
person’s hand during grounding will be discharged.
3. Service integrated control module or connecting
wiring following the discharge process in step 2. Use
caution not to recharge your body with static electricity;
(i.e., do not move or shuffle your feet, do not touch
ungrounded objects, etc.). If you come in contact with
an ungrounded object, repeat step 2 before touching
control or wires.
4. Discharge your body to ground before removing a new
control from its container. Follow steps 1 through 3 if
installing the control on a furnace. Return any old or
new controls to their containers before touching any
ungrounded object.
Diagnostic Chart
Refer to the
Troubleshooting Chart
in the back of this manual
for assistance in determining the source of unit operational
problems.
External Lockout
-
A control lockout resulting from an external fault
sensed by the control, such as an unsuccessful
recycle or retry period, or a limit trip. Once in
External Lockout, the control will shut down for a
period of one hour before attempting another trial
for ignition.
Internal Lockout
-
A failure internal to the control board.
Fault Recall
Retrieving Fault Codes
Resetting From Lockout
Furnace lockout results when a furnace is unable to achieve
ignition after three attempts during a single call for heat. It is
characterized by a non-functioning furnace and a one flash
diagnostic LED code. If the furnace is in “lockout”, it can be
reset in any of the following ways.
1. Automatic reset. The integrated control module will
automatically reset itself and attempt to resume normal
operations following a one hour lockout period.
2. Manual power interruption. Interrupt 115 volt power to
the furnace for 1 - 20 seconds.
3. Manual thermostat cycle. Lower the thermostat so that
there is no longer a call for heat then reset to previous
setting. Interrupt thermostat signal to the furnace for
1 - 20 seconds.
NOTE:
If the condition which originally caused the lockout
still exists, the control will return to lockout. Refer to the
Troubleshooting Chart
for aid in determining the cause.
Safety Circuit Description
A number of safety circuits are employed to ensure safe and
proper furnace operation. These circuits serve to control any
potential safety hazards and serve as inputs in the moni
-
toring and diagnosis of abnormal function. These circuits
are continuously monitored during furnace operation by the
integrated control module.
Integrated Control Module
The integrated control module will display furnace status
including faults, mode of operation and air flow, on three
seven segment displays.
Primary Limit
T
he primary limit control is located on the partition panel and
monitors heat exchanger compartment temperatures. It is
a normally-closed (electrically), automatic reset, tempera
-
ture-activated sensor. The limit guards against overheating
as a result of insufficient conditioned air passing over the
heat exchanger.
Auxiliary Limit
The auxiliary limit controls are located on or near the circula
-
tor blower and monitors blower compartment temperatures.
They are a normally-closed (electrically), manual-reset sen
-
sors. These limits guard against overheating as a result of
insufficient conditioned air passing over the heat exchanger.
Rollout Limit
The rollout limit controls are mounted on the burner/manifold
assembly and monitor the burner flame. They are normal
-
ly-closed (electrically), manual-reset sensors. These limits
guard against burner flames not being properly drawn into
the heat exchanger.
Pressure Switches
The pressure switches are normally-open (closed during
operation) negative air pressure-activated switches. They
monitor the airflow (combustion air and flue products) through
the heat exchanger via pressure taps located on the induced
draft blower and the coil front cover. These switches guard
against insufficient airflow (combustion air and flue products)
through the heat exchanger and/or blocked condensate drain
conditions.
Flame Sensor
The flame sensor is a probe mounted to the burner/manifold
assembly which uses the principle of flame rectification to
determine the presence or absence of flame.
Troubleshooting
Electrostatic Discharge (ESD)
Precautions
Use the following precautions during furnace installation
and servicing to protect the integrated control module from
damage. By putting the furnace, the control, and the person
at the same electrostatic potential, these steps will help
avoid exposing the integrated control module to electrostatic
