Condensate Drain Protection; Sequence Of Operation; Heating Mode; Cooling Mode - Carrier 58SMA Operating Instructions Manual

Step 3—Condensate Drain Protection
Freezing condensate left in condensate trap and drain line may
cause cracks, and possible water damage may occur. If freeze
protection is required, use condensate freeze protection accessory
or equivalent 3 to 6 watt per ft at 120v and 40°F self-regulating,
shielded, and waterproof heat tape. See Installation Instructions
supplied with accessory or heat tape manufacturer's recommenda-
tions.
1. Fold heat tape in half and wrap on itself 3 times.
2. Locate heat tape between sides of condensate trap back. (See
Fig. 37.)
3. Use wire ties to secure heat tape in place. Wire ties can be
positioned in notches of condensate trap sides. (See Fig. 37.)
4. Wrap field drain pipe with remaining heat tape, approximately
1 wrap per ft.
5. When using field-supplied heat tape, follow heat tape manu-
facturer's instructions for all other installation guidelines.
CONDENSATE TRAP
WIRE TIE(S)
HEAT TAPE
(3 WRAPS MINIMUM)
Fig. 37—Condensate Trap Heat Tape

SEQUENCE OF OPERATION

Furnace control must be grounded for proper operation, or
control will lock out. Control is grounded through green wire
routed to gas valve and burner box screw.
Using schematic diagram, follow sequence of operation through
different modes. (See Fig. 26.) This furnace has a new control
system. Read and follow wiring diagram carefully.
NOTE: If 115-v power supply to furnace or blower access panel
switch is interrupted during a call for heat, blower operates for 90
sec when power is restored before heating cycle is resumed.
Step 1—Heating Mode
When wall thermostat "calls for heat," R-W circuit closes. Furnace
control performs a self-check, verifies pressure switch contacts are
open, and starts inducer motor.
1. Prepurge period—As inducer motor comes up to speed,
pressure switch contacts close to begin a 15-sec prepurge
period.
2. Ignitor warm up—At end of prepurge period, ignitor is
energized for a 17-sec ignitor warm-up period.
3. Ignition sequence—When ignitor warm-up period is com-
pleted, gas valve opens, permitting gas flow to burners where
it is ignited. After 5 sec, ignitor is de-energized and a 2-sec
flame-sensing period begins.
HUM terminal on control center is energized with gas valve.
See Accessories — Humidifier section.
4. Flame sensing—When burner flame is sensed, control begins
blower on delay period and continues holding gas valve open.
If burner flame is not sensed, control center de-energizes gas
valve and ignition sequence is repeated.
NOTE: Ignition sequence repeats 3 additional times before a
lockout occurs. Lockout automatically resets after 3 hr or can be
manually reset by turning off 115v (not at thermostat) for 3 sec
minimum, then turning it on again.
5. Blower on delay—Sixty sec after burner flame is proven,
blower motor is energized on heating speed. Simultaneously,
electronic air cleaner terminal EAC-1 is energized.
6. Blower off delay—When thermostat is satisfied, circuit be-
tween R-W is opened, de-energizing gas valve (stopping gas
flow to burners) and humidifier. Blower motor and electronic
air cleaner remain energized for 135 sec.
7. Post purge—Inducer motor remains energized 15 sec after
burners are extinguished.
Step 2—Cooling Mode
When thermostat "calls for cooling," R-G and R-Y circuits close.
R-Y circuit starts outdoor condensing unit, and combined R-Y and
R-G circuit starts furnace blower motor on cooling speed. Elec-
tronic air cleaner EAC-1 terminal is energized with 115v whenever
blower is operating.
When thermostat is satisfied, R-G and R-Y circuits are opened,
furnace blower continues operating on cooling speed for an
additional 90 sec.
Step 3—Continuous Blower Mode
When R-G circuit is made, blower motor operates on heating
speed.
NOTE: Electronic air cleaner EAC-1 terminal is energized with
115v whenever blower is operating.
A93036
If a "call for heat" (R-W) occurs while thermostat is in continuous
blower mode, blower stops to allow furnace heat exchangers to
heat up more quickly, then restarts at end of blower on delay
period of 60 sec.
Blower reverts to continuous operation after heating cycle is
completed.
If a "call for cooling" (R-Y) occurs while thermostat is in
continuous blower mode, blower changes from continuous blower
speed (heating speed) to cooling speed.
When thermostat cooling call is satisfied, R-Y opens and blower
operates an additional 90 sec at cooling speed before reverting
back to continuous operation (heating speed).
Step 4—Heat Pump Mode
When installed with a heat pump, furnace control automatically
changes blower on delay timing sequence to avoid no blower
operation time during demand defrost cycles. When R-W and R-Y
or R-W, R-Y, and R-G thermostat inputs are received at the same
time at furnace control center, control starts blower in heating
speed. Then a gas heat mode begins. Blower remains operating at
heating speed for 15 sec or until end of prepurge period, then
blower shuts off until end of ignitor warm up and trial for ignition
periods (a total of 24 sec). Blower restarts at heating speed.
When R-W thermostat call disappears, control completes inducer
post-purge period (15 sec) and changes to cooling speed after a
2-sec delay.
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