the appropriate switch settings for your installation, see
Table 9 (page 35) for heating or Table 10 (page 36) for
Use ﬁ eld supplied wire to connect the thermostat's
dehumidiﬁ er output to the terminal marked DHUM. The
thermostat should be set so that the DHUM output is
high (positive) when dehumidiﬁ cation is needed. See also
Dehumidiﬁ cation Options section (page 27).
The variable speed control board is used
by other appliances. Many of the terminals
and connections on the board are for other
appliances and are not used in the two stage
application. The only two-stage ﬁ eld connection
to this board is the DHUM terminal, used to
reduce the blower speed during cooling.
START-UP & ADJUSTMENTS
Pre-Start Check List
Verify the polarity of the connections are correct, the
line voltage power leads are securely connected and
the furnace is properly grounded.
Verify that all needed thermostat wires are securely
connected to the correct leads on the terminal strip of
the circuit board. See Figures 24 - 26 (page 26).
Verify the gas line service pressure does not exceed
10.0 inches of water column, and is not less than 4.5
inches W.C. for natural gas. For LP gas the line service
pressure must not exceed 14 in. W.C., and must not be
less than 11.0 in. W.C.
Verify the roll-out and manual reset switch is closed.
If necessary, press the button to reset the switch. DO
NOT install a jumper wire across a switch to defeat
its function. If a switch reopens on start-up, DO NOT
reset the switch without identifying and correcting the
Verify the blower door is in place, closing the door switch
in the line voltage circuit.
Verify the gas line has been purged and all connections
are leak free.
Do not perform these steps until all of the checks in the
previous steps have been completed:
1. Set the thermostat to the lowest setting.
2. Turn off all electrical power to the furnace.
3. Follow the Operating Instructions on the furnace label.
4. Set the thermostat above room temperature and verify
the Operating Sequence. See page 29.
5. After 5 minutes of operation, set the thermostat below
room temperature and verify steps 11 & 12 of the
Verifying & Adjusting Input Rate
The input rate must be veriﬁ ed for each installation to
prevent over-ﬁ ring of the furnace. NOTE: The input rate
must not exceed the rate shown on the furnace rating plate.
At altitudes above 2,000 feet, it must not exceed that on
the rating plate less 4% for each 1,000 feet. To determine
the exact input rate, perform the following procedures:
1. Shut off all other gas ﬁ red appliances.
2. Start and run the furnace in high ﬁ re for at least 3
3. Measure the time (in seconds) required for the gas
meter to complete one revolution.
4. Convert the time per revolution to cubic feet of gas
per hour using Table 11 (page 37).
5. Multiply the gas ﬂ ow rate in cubic feet per hr by the
heating value of the gas in Btu per cubic ft to obtain
the input rate in Btuh. See example at top of page.
• Time for 1 revolution of a gas meter with a 1 cubic ft
dial = 40 seconds.
• From Table 11 read 90 cubic ft gas per hr.
• Local heating value of the gas (obtained from gas
supplier) = 1,040 Btu per cubic ft.
• Input rate = 1,040 x 90 = 93,600 Btuh.
6. The manifold pressure must be set to the appropriate
value for each installation by a qualiﬁ ed installer,
service agency or the gas supplier.
Do not attempt to drill the gas oriﬁ ces. Use only
factory supplied oriﬁ ces. Improperly drilled
oriﬁ ces may cause ﬁ re, explosion, carbon
monoxide poisoning, personal injury or death.
a.) Remove plastic cap from pressure regulator.
b.) Obtain the manifold pressure setting required for
this installation by referring to Table 13 (page 38)
for Propane or Tables 15 or 16 for Natural Gas
c.) Using an Allen wrench, turn the the LO Input
Adjusting Screw on the LO side of the regulator
to adjust the reduced input setting or turn the HI
Input Adjusting Screw on the side of the regulator
to adjust the full input setting. NOTE: Turning the
adjusting screw clockwise increases the pressure
and counterclockwise reduces the pressure. See
Figure 28 (page 29).
d.) Reinstall plastic cap after adjustment is complete.
Verifying & Adjusting Temperature Rise
Conﬁ rm the temperature rise through the furnace is
within the limits speciﬁ ed on the furnace rating plate. Any
temperature rise outside the speciﬁ ed limits could result
in premature failure of the heat exchanger.