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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 the information provided in Tables 2 and 3. 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.
High Altitude
In both the United States and Canada, this furnace is
approved for operation at altitudes from 0 to 4500 feet
above sea level without any required modifications. From
4500 to 7500 feet, the gas manifold pressure needs to be
adjusted according to the information shown in Tables 2
and 3. To adjust the manifold pressure, refer to previous
section Checking and Adjusting Gas Input. For installa-
tions above 7500 feet, call Technical Service at 1-800-448-
5872 ext. 2610 for assistance.
x
3600
x
=
Cubic Feet Per RevolutionBTU/HR
INPUT # Seconds Per Revolution
Heating
Value
Blower Control Board
The blower control board operates the circulating air
blower, the combustion blower, and any accessories
connected to it. These models feature user-selectable
blower “off” delay times (60, 90, 120, and 180 seconds)
that are factory set to provide a 120-second blower “off”
delay on heating (see wiring diagram on page 19).
Refer to the furnace wiring diagram while using the
following procedure to change motor speed:
1. Turn off electrical power to the unit.
2. Connect the desired speed tap for cooling on the
blower control board.
3. For heating speed, check the temperature rise and, if
necessary, adjust blower speed tap to maintain tempera-
ture rise within the range shown on furnace rating plate.
To use the same speed tap for both heating and
cooling, install a piggyback terminal on the speed tap
using a short jumper. Wire 1/4" quick connect termi-
nals on both ends to jumper the “HEAT” and “COOL”
speed on the blower control board.
4. The remaining speed taps must be connected to dummy
terminals marked “PARK” on the blower control board.
Checking and Adjusting Gas Input
The minimum permissible gas supply pressure for the
purpose of input adjustment is 5" W.C. for natural gas and
11" W.C. for propane gas. This furnace requires conversion
for use with propane (see Accessories section on page 18
for correct kit). The maximum inlet gas supply pressure is
10.5" W.C. for natural gas and 13" W.C. for propane.
Gas input must never exceed the value shown on the
furnace rating plate. This furnace is equipped for rated
input at manifold pressures of 3.5" W.C. for natural gas and
10.0" W.C. for propane gas.
The manifold pressure can be measured by removing the
pipe plug in the downstream side of the gas valve and
connecting a water manometer or gauge.
To adjust the regulator, turn the adjusting screw on the
regulator clockwise to increase pressure and input; coun-
terclockwise to decrease pressure and input.
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.
The furnace rate must be within +/– 2% of the
appliance rating input.
CAUTION
Failure to follow the safety warnings exactly
could result in dangerous operation, serious
injury, death, or property damage.
Improper servicing could result in dangerous
operation, serious injury, death, or property
damage.
• Before servicing, disconnect all electrical
power to furnace.
• When servicing controls, label all wires prior
to disconnecting. Reconnect wires correctly.
• Verify proper operation after servicing.
WARNING
ELECTRICAL SHOCK, FIRE,
OR EXPLOSION HAZARD
MAINTENANCE
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