20
Verifying and 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.
START-UP AND ADJUSTMENTS
Pre-Start Check List
√
V
erify the polarity of the connections are correct, the
line voltage power leads are securely connected and
the furnace is properly grounded.
√
V
erify the thermostat wires (
R
,
W
,
Y
, and
G
) are
securely connected to the correct leads on the
terminal strip of the circuit board.
√
V
erify the gas line service pressure does not exceed
10.0 inches of W.C., 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.
√
V
erify the roll-out and manual reset switch is closed. If
necessary, press the red button to reset a switch.
DO
NOT install a jumper wire across a switch to defeat
its function.
If a switch reopens on startup, DO NOT
reset the switch without identifying and correcting the
fault condition.
√
V
erify the blower door is in place, closing the door
switch in the line voltage circuit.
√
V
erify the gas line has been purged and all connections
are leak free.
Start-up Procedures
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 label attached
to the furnace.
4. Set the thermostat above room temperature and verify
the Operating Sequence (Page 21).
5. After 5 minutes of operation, set the thermostat
below room temperature and verify steps 9 - 10 of
the Operating Sequence.
Verifying and Adjusting Input Rate
IMPORTANT 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.
The input rate must be verifi ed for each installation to
prevent over-fi ring of the furnace. To determine the exact
input rate, perform the following procedures:
1. Shut off all other gas fi red appliances.
2. Start the furnace and run it for at least 3 minutes.
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 6 (page 32).
5. Multiply the gas fl ow rate in cubic ft per hr by the
heating value of the gas in Btu per cubic ft to obtain
the input rate in Btuh See example above.
Capscrew
Figure 16. Regulator Capscrew
Example
:
• Time for 1 revolution of a gas meter with a 1
cubic ft dial = 40 seconds.
• From Table 6 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.
WARNING:
Do not attempt to drill the gas orifi ces. Use
only factory supplied orifices. Improperly
drilled orifi ces may cause fi re, explosion,
carbon monoxide poisoning, personal injury
or death.
a.) Obtain the manifold pressure setting required for
this installation by referring to Table 8 (page 33)
for Propane or Tables 10 or 11 for Natural Gas
(page 34).
b.) Remove the regulator capscrew (Figure 16) from
the INLET side of the regulator.
c.) Slowly turn the adjustment screw inside the regulator
to obtain the appropriate manifold pressure.
NOTE: Turning the screw clockwise increases
the pressure and turning the screw counter-
clockwise decreases the pressure. To prevent
backing the screw all the way out from the valve,
turn the screw slowly.
d.) Replace and tighten the regulator capscrew over
the adjustment screw.
