SYSTEM OPERATION
47
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.
Burner Flame
Figure 57
TROUBLESHOOTING
Electrostatic Discharge (ESD) Precautions
NOTE: Discharge body’s static electricity before
touching unit. An electrostatic discharge can adversely
affect electrical components.
Use the following precautions during furnace instal-
lation and servicing to protect the integrated control
module from damage. By putting the furnace, the con-
trol, and the person at the same electrostatic potential,
these steps will help avoid exposing the integrated
control module to electrostatic discharge. This pro-
cedure 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 fur
-
nace 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 unground
-
ed object.
DIAGNOSTIC CHART
HIGH VOLTAGE !
T
O
AVOID
PERSONAL
INJURY
OR
DEATH
DUE
TO
ELECTRICAL
SHOCK
,
DISCONNECT
ELECTRICAL
POWER
BEFORE
PERFORMING
ANY
SERVICE
OR
MAINTENANCE
.
WARNING
Refer to the
Troubleshooting Chart
in the back of this
manual for assistance in determining the source of unit
operational problems. The 7-segment LED displays
will display an error code that may contain a letter and
number. The error code may be used to assist in trou-
bleshooting the unit.
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 an
code displayed on the 7-segment display. If
the furnace is in “lockout”, it will (or 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.
3. Manual thermostat cycle. Lower the thermostat so that
there is no longer a call for heat for 1 -20 seconds then
reset to previous setting.
NOTE: If the condition which originally caused the lock-
out still exists, the control will return to lockout. Refer
to the
Troubleshooting Chart
for aid in determining the
cause.
