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4.
After allowing unit to stabilize for 5 minutes, record
manifold pressure and compare to value given in
Table 12.
NOTE: Shut unit off and remove manometer as soon as an
accurate reading has been obtained. Take care to remove
barbed fitting and replace threaded plug.
Manifold Pressure
Between 2000 and 7500 ft, certain units require manifold
pressure adjustments specified in Table 12. Manifold
pressure should be measured, and adjusted as required
during unit start up.
NOTE: LP/Propane installations require a gas conversion
Orifice Kit as specified in Table 14.
Proper Combustion
Furnace should operate a minimum 15 minutes with correct
manifold pressure and gas flow rate before checking
combustion. Take combustion sample beyond the flue out
let and compare to the tables below. The maximum carbon
monoxide reading should not exceed 100 ppm.
Capacity
CO
-045
-070
-090
-110
-135
Table 11.
0 - 2000 ft.
Capacity
Nat.
Gas
045
070
090
3.5
110
135
Manifold pressure adjustments based on 1020 Btu/ft3 gas for natural and 2500 Btu/ft
1
Consult local utility for actual local heating value.
A natural to LP/Propane gas conversion Orifice Kit is required to convert this unit. Refer to kit instructions for conversion procedure.
2
A high altitude natural Orifice Kit is required.
3
507330-03G / 31-5000662
% for Nat
CO
% for LP
2
2
7.2 - 7.8
7.5 - 9.0
Manifold Pressure and Line Pressure at Various Altitudes
Manifold Pressure (in. w.c.)
2001 - 4500 ft.
LP
Nat.
LP
Gas
Gas
Gas
2
3.2
10.0
3.2
10.0
10.0
3.2
10.0
3.5
10.0
3.5
10.0
High Altitude
This furnace is carefully designed for optimal performance
under a wide range of operating conditions. To ensure
proper operation at higher altitudes, certain adjustments
and/or kits may be required.
Pressure Switch
Between 4501 and 7500 ft, some units may require a
pressure switch change. Table 14 lists the available
Pressure Switch Kits providing the minimum allowable
pressure switch set points, in this altitude range, for each
unit. The need for a Pressure Switch Kit may be evaluated
by comparing the pressure measured at the pressure
switch under steady state conditions (after 15 minutes of
run time) against the as shipped switch set point. Insufficient
negative pressure may lead to nuisance pressure switch
trips and possible unit lock outs.
Above 7500 feet, all units require both a burner orifice
change and a pressure switch change per Table 14.
1
4501 - 7500 ft.
Nat.
LP
Gas
Gas
2
2
3.0
10.0
2.8
10.0
2.7
9.6
3.0
9.6
2.9
9.6
Table 12.
Issue 2209
Line Pressure (in. w.c.)
7501 - 10000 ft.
Minimum
Nat.
LP
Nat.
Gas
Gas
Gas
3
2
3.5
10.0
4.5
gas for LP (corrected to standard conditions).
3
Max.
LP
Nat. &
Gas
LP
2
11.0
13.0
Page 27 of 36
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