ICP N9MSB0401410B, Service And Technical Support Manual

SERVICE AND TECHNICAL SUPPORT MANUAL

Gas Furnace: N9MSB

Specifications  subject to change without notice.

440 04 4412 01

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

!

Figure 6

Multipoise Orientations

A93041

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

Figure 6

, you must revise your orientation to component

location accordingly.

Electrical Controls and Wiring

Each pressure switch is labeled with the reference location

(noted as “COLLECTOR BOX

−

LPS” or “HOUSING

−

HPS” ON

THE SWITCH). The nominal break point of each switch is

shown on the label below the reference location in inches of

water column, “W.C.” The maximum and minimum break point

of the switch is +/

−

 0.05 inches of water column from the

nominal break point of the switch. The maximum make point of

the switch is 0.10 inches of water above the maximum break

point of the switch

Example:

 Nominal break point on pressure switch is 0.68

−

in.

W.C. The minimum break point of the switch is 0.63

−

in. W.C.

The maximum break point of the switch is 0.73

−

in. W.C. The

maximum make point of the switch is 0.83

−

in. W.C.

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 

Figure 7

 for field wiring

information and to 

Figure 15

 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 

Figure 4

) 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 

Figure 14

—Service Label)

The Troubleshooting Guide 

−

 Flow Chart (See 

Figure 16

) 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.