21
WARNING:
The reduction of input rating necessary for high
altitude installation may only be accomplished
with factory supplied orifi ces. Do not attempt
to drill out orifi ces in the fi eld. Improperly
drilled orifi ces may cause fi re, explosion,
carbon monoxide poisoning, personal injury
or death.
The furnaces are shipped from the factory with orifi ces
and gas regulator settings for natural gas operation at sea
level altitudes. At 2000 feet, the NFGC requires that this
appliance be derated 4% for each 1000 feet of altitude. For
example, the input needs to be reduced 8% at 2,000 feet,
12% at 3,000 feet and etc. This deration is in reference to
the input rate and gas heating value at sea level.
To derate the furnace requires knowing the heating value of
the gas at the installation site. Heating values at particular
job sites vary for two reasons:
1. The chemical mixture of the gas varies from region
to region and is expressed as the “sea level heating
value”.
2. The heating value varies by altitude. For this reason,
especially in high altitude areas, the local gas utility
specifi es the heating value at the residence’s gas
meter as the “local value”.
For added fl exibility, two tables have been provided for
natural gas installations with high or low heating values at
sea level.
T
ables 12 and 13 (page 37) contain the manifold
pressure and orifi ce sizes to use at various altitudes. Table
12 (HIGH) is for natural gas installations with a heating
value of more than 1,000 Btu per cubic foot and Table
13 (LOW) is for less than 1,000 Btu per cubic foot. To
determine which table to use:
1. Consult the local utility for the local heating value at
your installation site.
2. From Table 11 (page 36), fi nd your local heating value
as supplied by the utility company. Follow down the
column and stop at your altitude level.
3. If your sea level heating value is HIGH, use Table 12
or if it’s LOW, use Table 13. (See example below.)
After changing the regulator pressure or the orifi ces, it is
required that you measure the gas input rate. This may be
accomplished in the usual way, by clocking the gas meter
and using the local gas heating value. See Verifying and
Adjusting the Input Rate section (page 23).
IMPORTANT NOTE: Observe the action of the burners
to make sure there is no yellowing, lifting or fl ashback
of the fl ame.
Conversion to LP/Propane
WARNING:
The furnace was shipped from the factory
equipped to operate on natural gas. Conversion
to LP/propane gas must be performed by
qualifi ed service personnel using a factory
supplied conversion kit. Failure to use the
proper conversion kit can cause fi re, explosion,
property damage, carbon monoxide poisoning,
personal injury, or death.
Conversion to LP/propane is detailed in the installation
instructions provided with the conversion kit. Generally,
this will require the replacement of the burner orifi ces and
the spring found under the cap screw on the pressure
regulator.
In the U.S. if installation is above 2,000 ft., refer to Table
10 (page 36) to determine the correct orifi ce size and
regulator pressure. When conversion is complete, verify
the manifold pressure and input rate are correct as listed
in the tables. Approved conversion kits are listed below:
• The United States LP/Propane Gas Sea Level and High
Altitude Conversion Kit (P/N 904914) is for LP/propane
conversion in the United States at altitudes between
2,000 ft. and 10,000 ft. above sea level.
Please follow
the instructions provided with the kit
.
• The Canadian LP/Propane Gas Sea Level and High
Altitude Conversion Kit (P/N 904915) is for LP/propane
conversions in Canada at altitudes between zero and
4,500 ft. above sea level.
Please follow the instructions
provided with the kit.
INSTALLATION EXAMPLE
Elevation:
................................................5,000 feet
Type of Gas:
.........................................Natural Gas
Local Heating Value of Gas:
............................750
Determine which natural gas table to use. From Table
11, fi nd 750 and follow down the column, stop at the
5,000 feet row. The heating value listed is LOW. Table
13 will be used to determine orifi ce size and manifold
pressure.
