506303-01 Page 31 of 40Issue 0938
For Natural Gas: Check the furnace rate by observing the
gas meter, when available, making sure all other gas
appliances are turned off. The test hand on the meter should
be timed for at least one revolution. Note the number of
seconds for one revolution.
x
3600
x
=
Cubic Feet Per RevolutionBTU/HR
INPUT # Seconds Per Revolution
Heating
Value
The heating value of the gas can be obtained from the local
utility company.
For Propane Gas: The only check for the furnace rate is to
properly adjust the manifold pressure using a manometer and
Table 4. Typical manifold set point for installations at altitudes
from 0 to 4500 feet above sea level is 10.0" W.C.
Temperature Rise
Check the temperature rise and, if necessary, adjust blower
speed to maintain temperature rise within the range shown
on the unit rating plate.
The furnace rate must be within +/- 2% of the appliance
rating input.
CAUTION
High Altitude
In both the United States and Canada, this furnace is approved
for operation at altitudes from 0 to 4500' above sea level
without any required modifications. From 4500' to 7500', the
gas manifold pressure needs to be adjusted according to the
information shown in Table 4. To adjust the manifold pressure,
refer to section Checking and Adjusting Gas Input. For
installations above 7500', call Technical Service at 1-800-448-
5872 for assistance.
For installations above 4500 feet fill in the appropiate
information on the furnace label that has the words “This
furnace was converted on . . . . . . . . “.
For installation above 4,000 ft. refer to seciton Vent Pipe Size
and Length on page 7 and Figure 4 on page 7 Vent Pipe
Sizing.
Emergency Replacement Motor Operation (G2D95CT/
U Models Only)
If the variable speed motor in a G2D95CT/U furnace needs to
be replaced in an emergency situation (such as “no heat”)
and an exact replacement motor is not immediately available,
a standard PSC motor of equivalent frame size, voltage,
rotation, and horsepower can be temporarily installed until
the correct replacement motor can be obtained.
Manifold Pressure vs. Altitude
Table 4
* Consult local utility for actual heating value.
Furnace Input = Input Factor x Nameplate Input
Above 7500 feet, call Technical Services at 1-800-448-5872.
Altitude
(ft.)
Natural Gas
Propane
Heating
Value*
(Btu/ft³)
Manifold
Pressure
Low Fire
(in. w.c.)
Manifold
Pressure
High Fire
(in. w.c.)
Heating
Value*
(Btu/ft³)
Manifold
Pressure
Low Fire
(in. w.c.)
Manifold
Pressure
High Fire
(in. w.c.)
Input
Factor
2000
3000
4000
4500
5000
5500
6000
6500
7000
7500
948
914
881
865
849
833
818
802
787
771
1.70
1.70
1.70
1.70
1.61
1.60
1.59
1.58
1.57
1.56
3.50
3.29
3.27
3.25
3.23
3.21
3.19
3.50
3.50
3.50
2278
2196
2116
2077
2039
2000
1964
1927
1891
1853
4.90
4.90
4.90
4.90
4.61
4.58
4.55
4.53
4.50
4.47
10.00
10.00
10.00
10.00
9.41
9.35
9.29
9.24
9.18
9.12
0.9666
0.9499
0.9332
0.9249
0.8900
0.8790
0.8680
0.8570
0.8460
0.8350
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