Condensate Drain Protection; Sequence Of Operation; Self-Test Mode; Heating Mode - Carrier 58MVP Installation, Start-Up, And Operating Instructions Manual

OPEN STAND
PIPE FOR
A/C OR
HUMIDIFIER
DRAIN
TEE
TO OPEN
DRAIN
→ Fig. 44—Example of Field Drain Attachment
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. 45.)
→
3. Use wire ties to secure heat tape in place. Wire ties can be
positioned in notches of condensate trap sides. (See Fig. 45.)
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. 45—Condensate Trap Heat Tape
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 (see Fig. 24), follow sequence of
operation through different modes. 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 at
low-heat speed for 60 sec when power is restored before heating
cycle is resumed.
Step 1—Self-Test Mode
The control center goes through a brief self-test whenever 115-v or
24-v power is interrupted. The self-test takes approximately 2 sec
to complete. After power is restored, red (microprocessor) LED
briefly comes on. Then green LED comes on for 1 sec, followed by
1 sec where both yellow and green LEDs are on. During this time,
the microprocessor is checking itself.
Step 2—Heating Mode
A94054
When thermostat calls for heat, R-W/W1 circuit closes.
1. Prepurge period—The inducer motor is turned on and slowly
comes up to speed. When low-pressure switch closes, inducer
motor RPM is noted by microprocessor, and a 25 sec prepurge
period begins. The RPM is used to evaluate vent system
resistance. This evaluation is then used to determine required
RPM necessary to operate inducer in low-heat mode.
NOTE: The heat cycle can start in either high or low heat. If a
high-heat cycle is initiated, the inducer continues increasing its
speed after low-pressure switch closes. When high-pressure switch
closes, inducer motor RPM is noted by microprocessor before the
25 sec prepurge period begins. The RPM is used to evaluate vent
system resistance. This evaluation is then used to determine
required RPM necessary to operate inducer in high-heat mode.
2. Humidifier (HUM)—The HUM terminal is energized after
the inducer prepurge period is completed.
3. Ignitor warm up—At end of prepurge period, the hot surface
ignitor (HSI) is energized for a 17-sec HSI warm-up period.
4. Ignition sequence—After HSI ignitor warm-up period is
completed, the gas valve opens, permitting gas flow to burners
where it is ignited. After 5 sec, the HSI is de-energized, and a
2-sec flame-sensing period begins.
NOTE: The initial heat mode after 115-v or 24-v power interrup-
tion will be LOW HEAT. Low heat remains energized for 16
minutes before high heat is initiated, providing thermostat is still
calling for heat.
After initial cycle, the microprocessor evaluates the length of low-
and high-heat operating times and calculates optimum length of
low and high heat for next heat cycle. This accommodates the heat
load requirement seen as a result of thermostat operating time.
5. Flame sensing—When burner flame is sensed, the control
center holds gas valve open and begins blower on delay
period.
NOTE: Ignition sequence repeats 3 additional times before a
lockout occurs. Lockout automatically resets after 3 hr, or can be
manually reset by turning 115-v or 24-v power off (not at
thermostat) for 3 sec minimum, then turning on again.
6. Inducer speed operation—If cycle starts in low heat, inducer
speed reduces slightly after flame sense. If cycle starts in high
A93036
heat, inducer speed increases 15 sec after flame sense. The
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SEQUENCE OF OPERATION