16
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, 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. Tables 12 and 13 (page 40) contain the orifi ce
sizes and manifold pressure 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 39), 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.
After the gas piping to the furnace is complete, all
connections must be tested for gas leaks. This includes
pipe connections at the main gas valve, emergency shutoff
valve and fl exible gas connectors (if applicable). The soap
and water solution can be applied on each joint or union
using a small paintbrush. If any bubbling is observed,
the connection is not sealed adequately and must be
retightened. Repeat the tightening and soap check process
until bubbling ceases.
IMPORTANT NOTE: When pressure testing gas supply
lines at pressures greater than 1/2 psig (14 inch W.C.),
the gas supply piping system must be disconnected
from the furnace to prevent damage to the gas control
valve. If the test pressure is less than or equal to 1/2
psig (14 inch W.C.), close the manual shut-off valve.
High Altitude Application
High altitude conversion with this furnace depends on the
installation altitude and the heating value of the gas. The
installation of this furnace at altitudes above 2,000 feet
must meet the requirements of the National Fuel Gas
Code or local jurisdiction. In Canada, the requirements for
high altitude are different and governed by CGA B149.1.
Please consult your local code authority.
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
Installation Example
Elevation:
.................................................. 5,000 feet
Type of Gas:
........................................... Natural Gas
Local Heating Value of Gas:
.............................. 750
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.
After changing the regulator pressure or changing 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 & Adjusting the Input Rate section (page 22).
IMPORTANT NOTE: Observe the action of the burners
to make sure there is no yellowing, lifting or fl ashback
of the fl ame.
RISQUE D’INDENDIE OU D’EXPLOSION
Le non-respect des avertissements de
sécurité pourrait d’entraîner des blessures
graves, la mort ou des dommages matériels.
Ne jamais utiliser une fl amme nue por vérifi er la
présence des fuites de gaz. Pour la vérifi cation
de tous les joints, utiliser plutôt une solution
savonneuse commerciale fabriquée spécifi quement
pur la détection des fuites de gaz. Un incendie ou
une explosion peut entraîner des dommages
matériels, des blessures ou la mort.
AVERTISSEMENT:
