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SERVICING
c. Manifold pressure for 1 stage heat models and
high stage for 2 stage heat models should be 10"
w.c.
.
Mode
White-Rogers Model 36J22 Connected to
Manometer
.
Mode
White-Rogers Model 36J54 Connected to
Manometer
Manifold Gas Pressure
Natural Gas
Propane Gas
Single Stage
Manifold Gas Pressure
Gas
Natural
Low Stage
High Stage
Propane
Low Stage
High Stage
If operating pressures differ from above, make necessary
pressure regulator adjustments, check piping size, etc.,
and/or consult with local utility.
3.5" w.c.
10.0" w.c.
Range
Nominal
1.6 - 2.2" w.c.
2.0" w.c.
3.2 - 3.8" w.c.
3.5" w.c.
5.7 - 6.3" w.c.
6.0" w.c.
9.7 - 10.3" w.c.
10.0" w.c.
Two Stage
Checking For Delayed Ignition
Delayed ignition is a delay in lighting a combustible mixture
of gas and air which has accumulated in the combustion
chamber.
When the mixture does ignite, it may explode and/or rollout
causing burning in the burner venturi.
If delayed ignition should occur, the following should be
checked:
1. Improper gas pressure - adjust to proper pressure.
Improper burner positioning - burners should be in
locating slots, level front to rear and left to right.
2. Carry over (lighter tube or cross lighter) obstructed -
clean.
3. Main burner orifice(s) deformed, or out of alignment to
burner - replace.
Checking For Flashback
Flashback will also cause burning in the burner venturi, but
is caused by the burning speed being greater than the gas-
air flow velocity coming from a burner port.
Flashback may occur at the moment of ignition, after a
burner heats up or when the burner turns off. The latter is
known as extinction pop.
Since the end results of flashback and delayed ignition
can be the same (burning in the burner venturi) a definite
attempt should be made to determine which has occurred.
If flashback should occur, check for the following:
1. Improper gas pressure - adjust to proper pressure.
Check burner for proper alignment and/or replace
burner.
2. Improper orifice size - check orifice for obstruction.
Checking Pressure Control
A pressure control device is used to measure negative
pressure at the induced draft blower motor inlet to detect a
partial or blocked flue.
Pressure Switch Operation
(DSI Direct Spark System)
The pressure switch is ignored unless there is a call for
heat. When the control receives a call for heat, the control
checks to see that the pressure switch is open. If the
control sees that the pressure switch is closed before the
induced draft blower is energized, the LED will flash a code
of "2" (to indicate the pressure switch is stuck closed) and
the inducer will remain off until the pressure switch opens.
If the pressure switch opens before the ignition period, the
induced draft blower will remain on and the control will stay
in pre-purge until the pressure switch is closed for an entire
15 second pre-purge period. The LED will flash a code of
"3" to indicate open pressure switch.
38
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