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• If a humidistat is not available, it is an acceptable option
to connect the R & DEHUM via a field supplied normally
open relay. See
Figure 26 (page
terminals should be connected across the normally open
relay terminals. The O (B) & C terminals should then be
connected across the relay coil. This option causes the
blower to run at a reduced CFM for 10 minutes after a
call for cooling.
Heat Anticipator
Set the heat anticipator according to the instructions
supplied by the thermostat manufacturer. To determine
the heat anticipator setting:
1. Add the current draw of the system components; or
2. Measure the current flow on the thermostat R &W circuit
after the circulating blower motor has started.
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
24 (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
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
5. After 5 minutes of operation, set the thermostat below
room temperature and verify steps 11 & 12 of the
Operating Sequence.
Verifying & Adjusting Input Rate
The input rate must be verified for each installation to
prevent over-firing of the furnace. NOTE: The input rate
must not exceed the rate shown on the furnace rating plate.
28
27). The R & DEHUM
Figure
22,
Figure
23, &
Figure
page
30.
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 fired appliances.
2. Start and run the furnace in high fire 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 9 (page
5. Multiply the gas flow 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 below.
Example:
• Time for 1 revolution of a gas meter with a 1 cubic
ft dial = 40 seconds.
• From
Table 9
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 qualified installer, service
agency or the gas supplier.
WARNING:
Do not attempt to drill the gas orifices. Use only
factory supplied orifices. Improperly drilled
orifices may cause fire, 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
37)
for Propane or
38)
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. See
NOTE: Turning the adjusting screw clockwise
increases the pressure and counterclockwise
reduces the pressure.
d.
Reinstall plastic cap after adjustment is complete.
Verifying & Adjusting Temperature Rise
Confirm the temperature rise through the furnace is
within the limits specified on the furnace rating plate. Any
temperature rise outside the specified limits could result
in premature failure of the heat exchanger.
1. Place thermometers in the return and supply air stream
as close to the furnace as possible. To avoid false
readings, the thermometer on the supply air side must be
shielded from direct radiation from the heat exchanger.
36).
Table 11 (page
Table 13
&
Table 14 (page
Figure 27 (page
29).
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