Service And Maintenance Procedures; Pressure Switches - International comfort products R9MSB Service And Technical Support Manual

NOTES:
1. A filter is required for each return−air inlet. Airflow performance includes a 3/4 in. (19 mm) washable filter media such as contained in
factory− authorized accessory filter rack. See accessory list. To determine airflow performance without this filter, assume an additional
0.1 in. W.C. available external static pressure.
2. ADJUST THE BLOWER SPEED TAPS AS NECESSARY FOR THE PROPER AIR TEMPERATURE RISE FOR EACH INSTALLATION.
3. Shaded areas indicate that this airflow range is BELOW THE RANGE ALLOWED FOR HEATING OPERATION. THESE AIRFLOW
RANGES MAY ONLY BE USED FOR COOLING.
4. Airflows over 1800 CFM require bottom return, two−side return, or bottom and side return. A minimum filter size of 20" x 25" is required.
5. For upflow applications, air entering from one side into both the side of the furnace and a return air base counts as a side and bottom return.
6. All airflows that are shown in BOLD exceed 0.58 Watts per CFM at the given external static pressure.
SERVICE AND MAINTENANCE
PROCEDURES
Untrained personnel can perform basic maintenance func-
tions such as cleaning and replacing air filters. All other opera-
tions must be performed by trained service personnel. A quali-
fied service person should inspect the furnace once a year.
WARNING
!
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.
CAUTION
!
ENVIRONMENTAL HAZARD
Failure to follow this
environmental pollution.
Remove and recycle all components or materials (i.e.
oil, refrigerant, control board, etc.) before unit final
disposal.
WARNING
!
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.
CAUTION
!
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.
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
440 04 6601 01
caution may result in
Specifications subject to change without notice.
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

Pressure Switches

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.
WARNING
!
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.
The electrical ground and polarity for 115−v wiring must be
properly maintained. Refer to Figure 7 for field wiring
information and to Figure 16 for furnace wiring information.
NOTE: If the polarity is not correct, the STATUS LED on the
control will flash rapidly 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 2.) 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 will display status
code 24 when fuse needs to be replaced.
Troubleshooting
Refer to the service label. (See Figure 5—Service Label.)
The Troubleshooting Guide (See Figure 15) 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 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 amber
furnace control LED is either ON continuously, rapid
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