SERVICING
43
Pressure Regulator
Adjustment
(Under Cap Screw)
Gas Valve
On/Off
Selector
Switch
INLET
OUTLET
Inlet Pressure
Tap
Outlet Pressure
Tap
Gas Valve On/Off
Selector Switch
Inlet
Pressure
Ta p
Pressure Regulator
(under cap screw)
Outlet
Pressure
Ta p
Rate
High Stage 9.7 to 10.3" w.c. 10.0" w.c.
Low Stage 5.7 to 6.3" w.c.
6.0" w.c.
Single stage furnaces use a 115 volt silicon carbide igniter
(p/n 0130F00008) with 17-second warm up time.
D
ISCNNEC
ALL
PWER ERE SERVICING
WARNING
1. Remove burner compartment door to gain access to the
ignitor.
2. Ignitor cool - approximately 70 - 77°F.
3. Disconnect the ignitor from the Ignition Control.
4. Using an ohmmeter measure the resistance of the ignitor:
-at room temperature a normal reading will be 37 - 68
ohms.
5. Reconnect ignitor.
L
INE VLAGE NW PRESEN
WARNING
6. Place unit in heating cycle, measure current draw of ignitor
during preheat cycle.
Flashback will also cause burning in the burner venturi, but is
caused by the burning speed being greater than the gas-air
ow velocity coming from a burner port.
Flashback may occur at the moment of ignition, after a burner
heats up or when the burner turns o. The latter is known as
extinction pop.
Since the end results of ashback and delayed ignition can
be the same (burning in the burner venturi) a denite attempt
should be made to determine which has occurred.
If ashback should occur, check for the following:
1. Improper gas pressure - adjust to proper pressure (See
S-307 CHECKING GAS PRESSURE)..
2. Check burner for proper alignment and/or replace burner.
3. Improper orice size - check orice for obstruction.
The pressure control is a safety device to prevent the
combustion cycle from occurring with inadequate venting
caused by a restricted or blocked vent pipe.
WARNING
IG
VLAGE
D
ISCNNEC
ALL
PWER ERE SERVICING R
INSALLING IS NI
M
LIPLE PWER SRCES MA
E PRESEN
AILRE D S MA CASE PRPER
DAMAGE PERSNAL INJR R DEA
1. Remove burner compartment door to gain access to
pressure switch(es).
2. Remove wires from the pressure switch(es) electrical
terminals.
3. Remove the pressure control hose from the control and
interconnect with an inclined manometer as shown in the
following gures.
With a call for heat and the inducer running, check across the
pressure switch contacts with an ohm meter. If the contacts
are not closed, compare the negative reading on the inclined
manometer with the rating on the pressure switch to determine
whether the switch is defective or if the negative pressure is
inadequate to close the switch.
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*
M
1
2
3P
C
ON
O
F
F
A high altitude kit is required for installationsabove 7,000 ft.
Refer to the accessory matrix in this manual to determine
the proper natural gas and LP gas high altitude kit for your
furnace.
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