Carrier 58DE - Manual (Page 3)

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the wires pass from the thermostat should, be adequately
sealed with suitable material to prevent drafts" from affect­
ing the thermostat.
VI. SEQUENCE OF OPERATION
A. Heating (See Figure 8)
When the thermostat calls for heat, power from the trans­
former simultaneously energizes the pilot gas valve (inside
of main gas valve), spark igniter, and heat-assist coil in the
fan switch.
When the pilot flame is established, the flame sensing probe
acts to energize the main gas valve, permitting gas flow to
the burners. The electrode will continue to spark for approx­
imately 5 to 10 seconds after pilot flame is established. The
blower motor will be energized through the fan switch by
means of the heat assist and temperature rise in the heat ex­
changer.
When the thermostat is satisfied, the circuit between R and
W is broken, deenergizing the pilot gas valve, and stopping
gas flow to both pilot and main burners. The main gas valve
also closes. When the fan switch opens its contacts, the
blower motor stops.
If the furnace overheats for any reason, the limit switch
opens, breaking the circuit to the pilot valve coil, closing the
pilot valve, and stopping gas flow to pilot and main burners.
The pilot and main burners continue to cycle until the fault
is corrected.
If there is a motor failure, clogged filters, blocked outlets,
etc, heat will build up in the blower compartment. The aux­
iliary limit senses heat in the blower compartment and its
contacts open, breaking the circuit to the low-voltage con­
trols. The auxiliary limit is a manual reset and will require
resetting before power can be restored to the low-voltage
controls.
B. Automatic Gas Control Valve
When the thermostat “calls for heat,” the pilot valve opens,
permitting gas flow to the pilot. When a pilot flame is estab­
lished, the sensing probe permits energizing of the automat­
ic main gas valve. Gas then flows to the main burners where
it is ignited by the pilot flanje. . ,
^
Tb shut off the gas manually: Turn knob from ON to OFF
position. When in OFF position, the main burners and the
pilot flame are extinguished.
C. Spark Ignition Pilot
Each furnace is equipped with a fully automatic spark-
ignited pilot. When the thermostat “calls for heat,” the
igniter is energized, sending a high-voltage charge to the
electrode located at the pilot. After a pilot flame is estab­
lished, sparking will continue for 5 to 10 seconds, and the
flame sensing probe permits the main gas valve to open.
D. Fan/Limit Control Operation
At the moment the main gas valve opens, the time-delay
mechanism of the control is energized. If, due to pilot out­
age, the control bimetal element does not sense a tempera­
ture change, the control will turn on the blower strictly by
means of the time-delay feature. If for any reason the time
delay is not energized, the control bimetal element will
bring on the blower when it senses a temperature rise of 70
degrees Fahrenheit (standard differential) above the turnoff
setting. During the blow-down period and after the ther­
mostat is satisfied, the control will turn the blower off at the
indicated setting sensed by the control bimetal element.
E. Cooling
When the thermostat “calls for cooling,” power from the
transformer energizes the blower relay coil, closing its con­
tacts, and energizing the blower motor on its cooling speed.
It continues to operate until the thermostat is satisfied.
When the thermostat is satisfied, the circuit to terminal (G)
is broken, deenergizing the blower relay coil which, in turn,
opens its contacts, stopping the blower motor.
VII. FILTER ARRANGEMENT
The two factory-supplied filters are shipped in the blower
compartment. After the return air duct has been connected
to the furnace, install the filters in a V-formation inside the
return air plenum. See Figure 9.
Figure 5—Floor Opening
TABLE lll-FLOOR OPENING DIMENSIONS
MODEL 58DE SIZE
050...................
080,100
125
150
13
16V2
20
23 y.
m
Figure 6—Furnace on a Concrete Slab
VIII. STARTUP AND ADJUSTMENT
In addition to the following information, refer to “Proce­
dures for Gas Furnace Installation” packaged with the unit.
Check heat exchanger tube mounting screws. Be sure all are
in place and tight.
A. Adjustment of Blower Speed
NOTE: Some units have a shipping bracket supporting the
shaft end of the motor. This bracket should be removed and
discarded.
Heating Models— lb change speed, unplug black wire ter­
minal connector and reinsert at desired speed.
Air Conditioning Models— Tb change cooling speed, unplug
black wire terminal connector and reinsert for desired speed.
For heating speed, unplug red terminal connector and rein­
sert for desired speed.
B. Automatic Gas Control Valve
The automatic gas valve controls the flow of gas to both pilot
and main burners. The manual valve is built into the auto­
matic gas valve body. The manual valve has only two posi­
tions: OFF and ON. It does not have an intermediate posi­
tion for pilot gas flow only.
If not already checked when lighting the main burner, check
the proper operation of this valve by moving the room ther­
mostat pointer above and below room temperature and
observing that the main burners light on “call for heat” and
go off when the pointer is moved below the room tempera­
ture setting.