28
441 01 2613 05
Specifications are subject to change without notice
Natural Gas Input Rating Check
The gas meter can be used to measure input to furnace. Check
with gas supplier for actual BTU content.
1. Turn
OFF
gas supply to all appliances other than furnace and
start furnace. Use jumper wire on R to W.
2. Time how many seconds it takes the smallest dial on the gas
meter to make one complete revolution.
Note:
If meter uses a 2 cubic foot dial, divide results (seconds) by
two.
Refer to
Example.
The Example is based on a natural gas BTU
content of 1,000 BTU’s per cubic foot.
Example (BTUH)
Natural Gas
BTU Content
per cubic foot
No. of Seconds
Per Hour
Time Per Cubic
Foot in
Seconds
BTU Per
Hour
1,000
3,600
48
75,000
1,000 x 3,600
÷
48 = 75,000 BTUH
To Determine the appliance kW input rate from a .05m
3
test dial
that has been clocked at 80 seconds for one complete revolution.
Example (kW)
Number of
seconds per
hour
Number of
seconds per
complete
rotation
Size of test dial
(.05m
3
)
kW
m
3
/h
3,600
80
.05
2.25
3,600
÷
80 x .05 = 7.2 m
3
/h
2.25m
3
/h x 10.35 kWh/m
3
= 23.28 kW
23.28 x 3.412
= 79,431 BTU
3. Remove jumper wire from R to W.
4. Relight all appliances and ensure all pilots are operating.
Orifice Sizing
NOTE:
Factory sized orifices for natural gas and Propane gas are
listed in the furnace Technical Support Manual.
Ensure furnace is equipped with the correct main burner orifices.
Refer to
Table 6
or
Table 7
for correct orifice size and manifold
pressure for a given heating value and specific gravity for natural
and propane gas.
Operation Above 2000
′
(610m)Altitude
FIRE, EXPLOSION, CARBON MONOXIDE
POISONING HAZARD
Failure to follow this warning could
result in personal injury, death, and/or property
damage.
This high
!
altitude gas
!
conversion shall be done by
a qualified service agency in accordance with the
Manufacturer’s instructions and all applicable
codes and requirements, or in the absence of local
codes, the applicable national codes.
!
WARNING
These furnace may be used at full input rating when installed at
altitudes up to 2000
′
. When installed above 2000
′
(610m), the
input must be decreased 2% (natural) or 4% (Propane) for each
1000
′
(305m) above sea level in the USA. In Canada, the input
rating must be derated 5% (natural) or 10% (Propane) for each
1000
′
above sea level. This may be accomplished by a simple
adjustment of manifold pressure or an orifice change, or a
combination of a pressure adjustment and an orifice change. The
changes required depend on the installation altitude and the
heating value of the fuel.
Table 6
&
Table 7
show the proper
furnace manifold pressure and gas orifice size to achieve proper
performance based on elevation above sea level for both natural
gas and propane gas.
To use the natural gas table, first consult your local gas utility for
the heating value of the gas supply. Select the heating value in the
first column and follow across the table until the appropriate
elevation for the installation is reached. The value in the box at the
intersection of the altitude and heating value provides not only the
manifold pressure but also the orifice size. In the natural gas tables
the factory
!
shipped orifice size is in bold (
42
). Other sizes must be
obtained from service parts.
High Altitude Input Rate =
Nameplate Sea Level Input Rate x (Multiplier) [USA]
Elevation
ft (m)
High Altitude Multiplier
Natural Gas
Propane Gas
2001
′
- 3000
′
(610
!
914)
0.95
0.90
3001
′
- 4000
′
(915
!
1219)
0.93
0.86
4001
′
- 5000
′
(1220
!
1524)
0.91
0.82
5001
′
- 6000
′
(1524
!
1829)
0.89
0.78
6001
′
- 7000
′
(1829
!
2134)
0.87
0.74
7001
′
- 8000
′
(2134
!
2438)
0.85
0.70
*
Based on mid
!
range of elevation.
National Excelsior Company
www.excelsiorhvac.com
Subject to change without notice.
