11
441 01 5001 00
MANIFOLD PRESSURE AND ORIFICE SIZE FOR HIGH ALTITUDE APPLICATIONS
Table 4
NATURAL GAS
MEAN ELEVATION FEET ABOVE SEA LEVEL
HEATING VALUE
BTU/CU. FT.
0 to
1999
2000 to
2999
3000 to
3999
4000 to
4999
5000 to
5999
6000 to
6999
7000 to
8000
800
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
850
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
900
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.4
²
wc
950
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.5
²
wc
3.3
²
wc
3.2
²
wc
3.1
²
wc
1000
3.5
²
wc
3.4
²
wc
3.3
²
wc
3.2
²
wc
3.0
²
wc
2.9
²
wc
2.8
²
wc
1050
3.2
²
wc
3.1
²
wc
3.0
²
wc
2.9
²
wc
2.7
²
wc
2.6
²
wc
2.5
²
wc
1100
2.9
²
wc
2.8
²
wc
2.7
²
wc
2.6
²
wc
2.5
²
wc
2.4
²
wc
2.3
²
wc
Orifice Size
#42
#42
#42
#42
#42
#42
#42
Table 5
PROPANE
MEAN ELEVATION FEET ABOVE SEA LEVEL
HEATING VALUE
BTU/CU. FT.
0 to
1999
2000 to
2999
3000 to
3999
4000 to
4999
5000 to
5999
6000 to
6999
7000 to
8000
2500
10.0
²
wc
10.0
²
wc
9.4
²
wc
10.0
²
wc
9.8
²
wc
8.8
²
wc
7.9
²
wc
Orifice Size
#54
#54
#54
#55
#55
#55
#55
NOTE:
NATURAL GAS DATA BASED ON 0.60 SPECIFIC GRAVITY. PROPANE DATA BASED ON 1.53 SPECIFIC GRAVITY. FOR
FUELS WITH DIFFERENT SPECIFIC GRAVITY CONSULT THE LATEST EDITION OF THE NATIONAL FUEL GAS CODE ANSI
Z223.1 and CAN B149.
NOTE:
The derating of these units at 2% (Natural) and 4% (L.P.)
has been tested and approved by AGA.
High Altitude Air Pressure Switch
Altitudes over 4,000
¢
require a different air pressure switch than
the one installed at thefactory. Check parts list for pressure switch
and consult your distributor for part number and availability. In
Canada, provincial codes may govern installation of switch.Check
with governing authorities.
Changing Orifices
1. After disconnecting power and gas supply to the furnace, re-
move the burner compartment door, exposing the burner
compartment.
2. Disconnect gas line and pilot tubing from gas valve so man-
ifold can be removed.
3. Disconnect wiring at gas valve. Be sure to note the proper
location of any and all electrical wiring disconnected.
4. Remove the four (4) screws holding the manifold and gas
valve to the manifold supports. Do not discard any screws.
See
Figure 6.
Figure 6
Manifold
25--23--51z
Some Models may vary
5. Carefully remove the manifold assembly.
6. Remove the orifices from the manifold and replace them with
proper sized orifices. See
Figure 7.
7. Tighten orifices so it is seated and gas tight. See
Figure 7.
