GMES8 GCES8 Service Manual
PRODUCT DESIGN
28
the proper amount of air into the burner. This may cause in-
complete combustion, ashback, and possible yellow tipping.
In some areas the gas supplier may articially derate the gas
in an effort to compensate for the effects of altitude. If the
gas is articially derated, the appropriate orice size must be
determined based upon the BTU/ft
3
content of the derated
gas and the altitude. Refer to the National Fuel Gas Code,
NFPA 54/ANSI Z223.1, and information provided by the gas
supplier to determine the proper orice size.
A different pressure switch may be required at high altitude
regardless of the BTU/ft
3
content of the fuel used. Refer to
the product Specication Sheet or Technical Manual for a
tabular listing of appropriate altitude ranges and correspond-
ing manufacturer’s pressure switch kits.
PROPANE GAS CONVERSION
WARNING
P
OSS
IBLE PROPERTY DAMAGE, PERSONAL INJURY OR DEATH MAY OCCUR IF
THE CORRECT CONVERSION KITS ARE NOT INSTALLED.
T
HE APPROPRIATE KITS
MUST BE APPLIED TO INSURE SAFE AND PROPER FURNACE OPERATION.
A
LL
CONVERSIONS MUST BE PERFORMED BY A QUALIFIED INSTALLER OR SERVICE
AGENCY.
This unit is congured for natural gas. The appropriate man-
ufacturer’s propane gas conversion kit, must be applied for
propane gas installations.
• Single-stage 80% furnace modelsusing a Honeywell
VR8215 single stage valve or a White-Rodgers 36J22
use LPT-03 LP Conversion Kit.
Refer to the specification sheet for the model you are
servicing. Refer to the “propane gas and/or High Altitude
Installations” section for details.
GAS VALVE
This unit is equipped with a 24 volt gas valve controlled
during furnace operation by the integrated control module.
As shipped, the valve is congured for natural gas. The
valve is eld convertible for use with propane gas by using
the appropriate propane gas conversion kit. Taps for mea-
suring the gas supply pressure and manifold pressure are
provided on the valve.
NOTE: The gas supply pressure on White-Rodger "J"
model gas valve, used on single stage furnaces, can be
checked with a gas pressure test kit (Part #0151K00000S)
available through our authorized distributors.
The gas valve has a manual ON/OFF control located on
the valve itself. This control may be set only to the “ON” or
“OFF” position. Refer to the Lighting Instructions Label or the
“Putting the Furnace Into Operation” section of this manual
or the installation instructions for use of this control during
start up and shut down periods.
GAS PIPING CONNECTIONS
CAUTION
T
O AVOID POSSIBLE UNSATISFACTORY OPERATION OR EQUIPMENT DAMAGE
DUE TO UNDERFIRING OF EQUIPMENT, USE THE PROPER SIZE OF
NATURAL/PROPANE GAS PIPING NEEDED WHEN RUNNING PIPE FROM THE
METER/TANK TO THE FURNACE.
The gas piping supplying the furnace must be properly sized
based on the gas ow required, specic gravity of the gas,
and length of the run. The gas line installation must comply
with local codes, or in their absence, with the latest edition of
the National Fuel Gas Code, NFPA 54/ANSI Z223.1.
Length of Nominal Black Pipe Size
Pipe in Feet 1/2" 3/4" 1" 1 1/4" 1 1/2"
10 132 278 520 1050 1600
20 92 190 350 730 1100
30 73 152 285 590 980
40 63 130 245 500 760
50 56 115 215 440 670
60 50 105 195 400 610
70 46 96 180 370 560
80 43 90 170 350 530
90 40 84 160 320 490
100 38 79 150 305 460
CFH =
(Pressure 0.5 psig or less and pressure drop of 0.3" W.C.; Based on 0.60 Specific
Gravity Gas)
Natural Gas Capacity of Pipe
In Cubic Feet of Gas Per Hour (CFH)
BTUH Furnace Input
Heating Value of Gas (BTU/Cubic Foot)
To connect the furnace to the building’s gas piping, the install-
er must supply a ground joint union, drip leg, manual shutoff
valve, and line and ttings to connect to gas valve. In some
cases, the installer may also need to supply a transition piece
from 1/2" pipe to a larger pipe size.
The following stipulations apply when connecting gas piping.
Refer to the following gures for typical gas line connections
to the furnace.
1. Use black iron or steel pipe and ttings for the building
piping.
2. Use pipe joint compound on male threads only. Pipe
joint compound must be resistant to the action of the
fuel used.
3. Use ground joint unions.
4. Install a drip leg to trap dirt and moisture before it can
enter the gas valve. The drip leg must be a minimum of
three inches long.
5. Install a 1/8" NPT pipe plug tting, accessible for test
gage connection, immediately upstream of the gas
supply connection to the furnace.
6. Use two pipe wrenches when making connection to
the gas valve to keep it from turning. The orientation of
the gas valve on the manifold must be maintained as
shipped from the factory.