Sequence Of Operation; Heating Mode - Carrier 58MSA Installation, Start-Up, And Operating Instructions Manual

Table 7—Maximum Allowable Exposed Vent Pipe Length (ft) With and Without Insulation in Winter Design
FURNACE
SIZE
040
060
080
100
120
* Pipe length (ft) specified for maximum pipe lengths located in unconditioned spaces. Pipes located in unconditioned space cannot exceed total allowable pipe length
as specified in Table 7.
† Insulation thickness based on R value of 3.5 per in.

SEQUENCE OF OPERATION

→
Furnace control must be grounded for proper operation, or
control will lock out. Control is grounded through
green/yellow wire routed to gas valve and burner box screw.
Failure to follow this caution will result in minor unit
operation.
Using the schematic diagram in Fig. 32, follow the sequence of
operation through the different modes. Read and follow the wiring
diagram very carefully.
NOTE: If a power interruption occurs during a call for heat (W),
the control will start a 90-second blower-only ON period two
seconds after power is restored, if the thermostat is still calling for
gas heating. The red LED light will flash code 12 during the
90-second period, after which the LED will be ON continuous, as
long as no faults are detected. After the 90-second period, the
furnace will respond to the thermostat normally.
The blower door must be installed for power to be conducted
through the blower door interlock switch ILK to the furnace
control CPU, transformer TRAN, inducer motor IDM, blower
motor BLWM, hot-surface igniter HSI, and gas valve GV.
1. Heating
(See Fig. 30 for thermostat connections.)
Temperature Ambient*
WINTER DESIGN
TEMPERATURE DIAMETER
(°F)
20
0
-20
20
0
-20
20
0
-20
20
0
-20
20
0
-20
20
0
-20
20
0
-20
20
0
-20
20
0
-20
MAX PIPE
WITHOUT
INSULATION
(IN.)
1.5 51
1.5 28
1.5 16
2 45
2 22
2 10
2 65
2 35
2 20
2 55
2 48
2 30
2.5 70
2.5 47
2.5 28
2.5 40
2.5 40
2.5 38
3 70
3 50
3 28
3 70
3 61
3 37
4 70
4 48
4 23
The wall thermostat "calls for heat", closing the R to W
circuit. The furnace control performs a self-check, verifies the
pressure switch contacts PRS are open, and starts the inducer
motor IDM.
a. Inducer Prepurge Period- As the inducer motor IDM
comes up to speed, the pressure switch contacts PRS close,
24 vac power is supplied for a field installed humidifier at
the HUM terminal and the control begins a 15-second
prepurge period.
b. Igniter Warm-Up- At the end of the prepurge period, the
Hot-Surface Igniter HSI is energized for a 17-second
igniter warm-up period.
→
c. Trial-for-Ignition Sequence- When the igniter warm-up
period is completed, the main gas valve relay contacts GVR
close to energize the gas valve GV, the gas valve opens.
The gas valve GV permits gas flow to the burners where it
is ignited by the Hot Surface Igniter HSI. Five seconds after
the GVR closes, a 2-second flame period begins. The HSI
igniter will remain energized until the flame is sensed or
until the 2-second flame proving period begins.
d. Flame-Proving- When the burner flame is proved at the
flame-proving sensor electrode FSE, the furnace control
CPU begins the blower-ON delay period and continues to
hold the gas valve GV open. If the burner flame is not
proved within two seconds, the control CPU will close the
gas valve GV, and the control CPU will repeat the ignition
sequence for up to three more Trials-For-Ignition before
33
WITH 3/8–IN. OR
THICKER INSULATION†
70
70
70
70
70
58
70
70
70
55
55
55
70
70
70
40
40
40
70
70
70
70
70
70
70
70
70