507330-01B
Issue 1809
Page 27 of 33
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
2
% for Nat
CO
2
% for LP
-070
7.2 - 7.8
7.5 - 9.0
-090
-110
Table 11.
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 12 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 12.
Fan Control
The fan on time of 45 seconds is not adjustable. The heat
fan off delay (amount of time that the blower operates after
the heat demand has been satisfied) may be adjusted by
changing the jumper position across the five pins on the
integrated control. The unit is shipped with a factory fan
off delay setting of 90 seconds. The fan off delay affects
comfort and is adjustable to satisfy individual applications.
Adjust the fan off delay to achieve a supply air temperature
between 90° and 110° F at the moment that the blower
is de-energized. Longer off delay settings provide lower
return air temperatures; shorter settings provide higher
return air temperatures. See Figure 35.
Figure 35. Heat Fan Off Time in Seconds
Orifice Kits and Pressure Switch Kits at Various Altitudes
Capacity
0 - 4500 ft.
4501 - 7500 ft.
7501 - 10000 ft.
Pressure
1
Switch Kit
Natural
to LP /
Propane
Orifice Kit
LP /
Propane
to Natural
Orifice Kit
Pressure
1
Switch Kit
Natural
to LP /
Propane
Orifice Kit
LP /
Propane
to Natural
Orifice Kit
Pressure
1
Switch Kit
Natural
Orifice Kit
LP /
Propane
Orifice Kit
070
As Shipped
(-0.68” w.c.)
11K50
2
(0.034”)
73W80
2
(0.063”)
80W52
(-0.60” w.c.)
11K50
2
(0.034”)
73W80
2
(0.063”)
80W51
(-0.55” w.c.)
51W01
(0.055”)
11K45
2
(0.032”)
090
As Shipped
(-0.65” w.c.)
80W52
(-0.60” w.c.)
80W51
(-0.55” w.c.)
110
As Shipped
(-0.68” w.c.)
80W57
(-0.65” w.c.)
80W52
(-0.60” w.c.)
1
Minimum allowable set points for this altitude range. Application of a Pressure Switch with lower set point (less negative / closer to zero) is not
permitted.
2
Kit contains burner orifices and gas valve regulator spring(s).
Table 12.
