Service Manual

SERVICING
55
Gas Valve On/Off
Selector Switch
Pressure Regulator
(under cap screw)
Outlet
Pressure
Ta p
Open to
A
tmosphere
Manifold
Pressure
Open to
Atmosphere
Inlet Pressure
Inlet
Pressure
Ta p
HONEYWELL MODEL VR8215 1-STAGE GAS VALVE
MEASURING INLET AND MANIFOLD GAS PRESSURE
With Power ON:
WARNING
Line Voltage now present.
3. Put furnace into heating cycle and turn on all other gas
consuming appliances.
For NATURAL GAS:
a. Inlet pressure should be a nominal 7" w.c.
b. (2 stage heat models only) Manifold pressure on
low stage should be 2.0” w.c. ± .3"w.c.
c. Manifold pressure for 1 stage heat models and
high stage for 2 stage heat models should be 3.5”
± .3"w.c.
For PROPANE GAS:
a. Inlet pressure should be a nominal 11" w.c.
b. (2 stage heat models only) Manifold pressure on
low stage should be 6" w.c.
c. Manifold pressure for 1 stage heat models and
high stage for 2 stage heat models should be 10”
w.c.
Manifold Gas Pressure
Natural Gas 3.5" w.c.
Propane Gas 10.0" w.c.
Single Stage
Range Nominal
Natural Low Stage 1.6 - 2.2" w.c. 2.0" w.c.
High Stage 3.2 - 3.8" w.c. 3.5" w.c.
Propane Low Stage 5.7 - 6.3" w.c. 6.0" w.c.
High Stage 9.7 - 10.3" w.c. 10.0" w.c.
Manifold Gas Pressure
Gas
Two Stage
If operating pressures differ from above, make necessary
pressure regulator adjustments, check piping size, etc.,
and/or consult with local utility.
S-308 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. (See
S-307)
2. Improper burner positioning - burners should be in
locating slots, level front to rear and left to right.
3. Carry over (lighter tube or cross lighter) obstructed -
clean.
4. Main burner orifice(s) deformed, or out of alignment to
burner - replace.
S-309 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. See
S-307.
2. Check burner for proper alignment and/or replace burner.
33. Improper orifice size - check orifice for obstruction.