Carrier 58MSA User Manual

Page 8

9. Verify ignitor operation by initiating control board self-test

feature or by cycling thermostat.

10. Replace main furnace door.

Step 7—Electrical Controls and Wiring

There may be more than 1 electrical supply to the unit. Check
accessories and cooling unit for additional electrical supplies.

The electrical ground and polarity for 115-v wiring must be
maintained properly. Refer to Fig. 11 for field wiring information
and to Fig. 15 for unit wiring information.

NOTE:

If the polarity is not correct, the STATUS LED on the

control center will flash rapidly and prevent the furnace from
operating. The control system also requires an earth ground for
proper operation of the control center and flame sensing.

The 24-v circuit contains an automotive-type, 3-amp fuse located
on the control center. (See Fig. 12.) Any direct 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 fuse of
identical size.

With power to the unit disconnected, check all electrical connec-
tions for tightness. Tighten all screws on electrical connections. If
any smoky or burned connections are found, disassemble the
connection, clean all parts, strip wire, and reassemble properly and
securely.

Reconnect electrical supply to unit and observe unit through 1
complete operating cycle. Electrical controls are difficult to check
without proper instrumentation; if there are any discrepancies in
the operating cycle, contact your dealer and request service.

Step 8—Checking Heat Tape Operation
(If Applicable)

In applications where the ambient temperature around the furnace
is 32°F or lower, freeze protection measures are required. If this

application is where heat tape has been applied, check to ensure it
will operate when low temperatures are present.

NOTE:

Heat tape, when used, should be wrapped around the

condensate drain trap and drain line. There is no need to use heat
tape within the furnace casing. Most heat tapes are temperature
activated, and it is not practical to verify the actual heating of the
tape. Check the following:

If this furnace is installed in an unconditioned space where
the ambient temperatures may be 32°F or lower, freeze
protection measures must be taken.

1. Check for signs of physical damage to heat tape such as nicks,

cuts, abrasions, gnawing by animals, etc.

2. Check for discolored heat tape insulation. If any damage or

discolored insulation is evident, replace heat tape.

3. Check that heat tape power supply circuit is on.

Fig. 11—Field Wiring

A98209

115-V

FIELD-SUPPLIED

DISCONNECT

AUXILIARY
J-BOX

CONTROL

BOX

24-V

TERMINAL

BLOCK

THREE-WIRE

HEATING-

ONLY

FIVE

WIRE

NOTE 1

NOTE 2

FIELD-SUPPLIED
DISCONNECT

CONDENSING
UNIT

TWO
WIRE

FURNACE

GND

FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-V WIRING

208/230- OR
460-V
THREE
PHASE

208/230-V
SINGLE
PHASE

WHT

BLK

WHT

BLK

NOTES:

Connect Y-terminal as shown for proper operation.
Some thermostats require a "C" terminal connection as shown.
If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.

GND

THERMOSTAT
TERMINALS

1.
2.
3.