SERVICING
37
A/GMVC, A/GCVC model furnaces have factory installed
#45 natural gas orices.
The only time resizing is required is when a reduction in
ring rate is required for an increase in altitude or a furnace
is being converted for use with L.P. gas.
Orices should be treated with care in order to prevent
damage. They should be removed and installed with a box-
end wrench in order to prevent distortion. In no instance
should an orice be peened over and re-drilled. This will
change the angle or deection of the vacuum eect or
entraining of primary air, which will make it dicult to adjust
the ame properly. This same problem can occur if an
orice spud of a dierent length is substituted.
WARNING
1. Check orice visually for distortion and/or burrs.
2. Check orice size by the number stamped on the orice.
The length of Dimension “A” determines the angle of Gas
Stream “B”.
A dent or burr will cause severe deection of the gas
stream.
Gas inlet and manifold pressures should be checked and
adjusted in accordance to the type of fuel being consumed.
The line pressure supplied to the gas valve must be within
the range specied below. The supply pressure can be
measured at the gas valve inlet pressure tap or at a hose
tting installed in the gas piping drip leg. The supply
pressure must be measured with the burners operating.
To measure the gas supply pressure, use the following
procedure.
WARNING
1. After turning off gas to furnace at the manual gas
shuto valve external to the furnace, remove burner
compartment door to gain access to the gas valve.
2. Connect a calibrated water manometer (or appropriate
gas pressure gauge) at either the gas valve inlet
pressure tap or the gas piping drip leg as shown in the
following gures.
3. Turn ON the gas and electrical power supply and operate
the furnace and all other gas consuming appliances on
the same gas supply line.
4. Measure furnace gas supply pressure with burners ring.
Supply pressure must be within the range specied in
the following table.
Minimum: 4.5” w.c. Maximum: 10.0” w.c.
Propane Gas Minimum: 11.0” w.c. Maximum: 13.0” w.c.
If supply pressure diers from above, make necessary
adjustments to pressure regulator, gas piping size, etc.,
and/or consult with local gas utility.
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