27
HI Input
Adjusting Screw
Lo Input
Adjusting Screw
Figure 27. HI and LO Input Adjusting Screws
Example
:
• Time for 1 revolution of a gas meter with a 1
cubic foot 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 foot.
• Input rate = 1,040 x 90 = 93,600 Btuh.
START-UP AND 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 21 - 23 (page 24).
√
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
fault condition.
√
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.
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 furnace label.
4. Set the thermostat above room temperature and verify
the Operating Sequence. See page 28.
5. After 5 minutes of operation, set the thermostat below
room temperature and verify steps 11 & 12 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 and run the furnace in high fi re 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 11 (page 38).
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.
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.) Remove plastic cap from pressure regulator.
b.) Obtain the manifold pressure setting required for
this installation by referring to Table 13 (page 39)
for Propane or Tables 15 or 16 for Natural Gas
(page 40).
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 (Figure 27) on the side of the
regulator to adjust the full input setting.
IMPORTANT
NOTE: Turning the adjusting screw clockwise
increases the pressure and counterclockwise
reduces the pressure.
d.) Reinstall plastic cap after adjustment is complete.
