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Your
Furnace
(Cont.)
AIR PROVING
SWITCH
LIMIT
CONTROL
IGNITOR/SENSOR
COMBUSTION
AIR BLOWER
EXHAUST
TEMPERATURE
UMIT SWITCH
ELECTRICAL
JUNCTION
BOX
DOOR INTERLOCK
ELECTRICAL
CONTROL
BOX
SYSTEM
RELAY
FAN RELAY
TRANSFORMER-115V
- 24V.
White Rodgers Valve
3'6
i i
-
E Series
Hot Surface
ignition
Honeywell
Valve _ 8204
Series
Spark to Pilot ignition
PRIMARY
HEAT EXCHANGER
GAS VALVE
FLAME ROLLOUT
SENSOR
SECONDARY
HEAT
EXCHANGER'
FAN CONTROL
ELECTRONIC
SPARK
MODULE
CIRCULATING
AIR BLOWER
FILTER (SHOWN
IN BOTTOM)
MAY BE MOUNTED
IN SIDE
THE OSTAT
FIG, 3
TYPICAL
UPFLOW
See separate
description under "Thermostat".
As the
temperature
in your home drops the thermostat
closes
and completes
a tow voltage
(24V)
control
circuit
to
the System
Relay inside the control
I_ox. This relay
closes
and provides
power
to the Electronic
Ignition
Module,
and Combustion
Air Blower. The thermostat
also completes
a circuit to an internal
heater inside
the Fan/Limit
Control.
This allows
more precise Fan
"ON"
control
to
help
maintain
comfortable
temperatures
in your home.
ELECTRONIC
SPARK
MODULE/GAS
VALVE
When the thermostat
calls for heat it completes
a Low
voltage
(24V)
circuit to the electronic
ignition
module.
The module either starts
an electric
spark or activates
a hot surface
ignitor to ignite the gas as the gas valve
opens
letting
gas through
to pilot or main
burner.
When the flame
is firmly
established
the module
will
shut off. For safety
it will automatically
restart
if the
flame is interrupted.
!f there is an abnormal
function,
the gas valve is designed
to automatically
shut off the
gas.
COMBUSTION
AIR BLOV#ER
The System
Relay closes to start the Combustion
Air
Blower
which
exhausts
the vent
gases out through
the vent pipe. The blower
creates
a pressure
differen-
tial inside the furnace which
provides
the right amount
of induced
draft
(air) to properly
control
combustion
for maximum
efficiency.
This part of the system
pro-
vides several
safety features
as the electrical
circuit
for the Electronic
Ignition
Module/Gas
Valve must
go
through a Flame Rol! Out Sensor, Air Proving
Switch,
Exhaust
Temperature
Limit
Switch
and
the
temperature
limit portion
of the Fan/Limit
Control.
If the right amount
of air is not going through
the fur-
nace or if temperatures
are too hot the electrical
cir-
cu=t to the Electronic
Ignition
Module/Gas
Valve
will
be interrupted.
6
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