SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: N9MSB
Specifications subject to change without notice.
440 04 4411 03
13
SERVICE AND MAINTENANCE
PROCEDURES
FIRE, INJURY OR DEATH HAZARD
Failure to follow this warning could result in personal
injury, death and/or property damage.
The ability to properly perform maintenance on this
equipment requires certain knowledge, mechanical
skills, tools, and equipment. If you do not possess
these, do not attempt to perform any service and
maintenance on this equipment other than those
procedures recommended in the Owner’s Manual.
!
WARNING
ENVIRONMENTAL HAZARD
Failure to follow this caution may result in
environmental pollution.
Remove and recycle all components or materials (i.e.
oil, refrigerant, control board, etc.) before unit final
disposal.
CAUTION
!
ELECTRICAL SHOCK, FIRE OR EXPLOSION
HAZARD
Failure to follow this warning could result in personal
injury or death, or property damage.
Before installing, modifying, or servicing system, main
electrical disconnect switch must be in the OFF
position and install a lockout tag. There may be more
than one disconnect switch. Lock out and tag switch
with a suitable warning label. Verify proper operation
after servicing.
!
WARNING
ELECTRICAL OPERATION HAZARD
Failure to follow this caution may result in improper
furnace operation or failure of furnace.
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation.
CAUTION
!
General
These instructions are written as if the furnace is installed in an
upflow application. An upflow furnace application is where the
blower is located below the combustion and controls section of
the furnace, and conditioned air is discharged upward. Since
this furnace can be installed in any of the 4 positions shown in
, you must revise your orientation to component
location accordingly.
Figure 6
Multipoise Orientations
A93041
Electrical Controls and Wiring
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal
injury or death.
There may be more than one electrical supply to the
furnace. Check accessories and cooling unit for
additional electrical supplies that must be shut off
during furnace servicing. Lock out and tag switch with
a suitable warning label.
!
WARNING
The electrical ground and polarity for 115
−
V wiring must be
properly maintained. Refer to
information and to
for furnace wiring information.
NOTE
: If the polarity is not correct, the STATUS LED on the
control will flash code 10 and prevent the furnace from heating.
The control system also requires an earth ground for proper
operation of the control and flame
−
sensing electrode.
The 24
−
V circuit contains an automotive
−
type, 3
−
amp. fuse
located on the control. (See
) Any shorts of the 24
−
V
wiring during installation, service, or maintenance will cause
this fuse to blow. If fuse replacement is required, use ONLY a
3
−
amp. fuse. The control LED display will be off when fuse
needs to be replaced.
Troubleshooting
Refer to the service label. (See
—Service Label)
The Troubleshooting Guide
−
) can
be a useful tool in isolating furnace operation problems.
Beginning with the word “Start,” answer each question and
follow the appropriate arrow to the next item.
The Guide
−
Flow Chart will help to identify the problem or
failed component. After replacing any component, verify correct
operation sequence.
Proper instrumentation is required to service electrical controls.
The control in this furnace is equipped with a Status Code LED
(Light
−
Emitting Diode) to aid in installation, servicing, and
troubleshooting. Status codes can be viewed at the indicator in
blower door. The green furnace control LED is either ON
heartbeat, off or a code composed of 1 or 2 digits. The first digit
is the number of short flashes, the second digit is the number of
long flashes.
