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The integrated control starts the circulating air blower
30 seconds after the gas valve is opened. The control is
factory wired to turn the blower motor off 90 - 135 seconds
after the gas valve is closed.
ECM Motors: The heating blower off delay is factory
set at 90 seconds. An additional 45 second off delay is
programmed into the ECM blower motor for a total of
135 seconds.
PSC Motors: A moveable jumper is provided to select
between four heat blower off delay times - 60, 90, 120,
and 180 seconds. The control is shipped with the jumpers
in the 120 second position. The control defaults to 90
seconds if the jumper is not attached.
Verifying & Adjusting Firing Rate
CAUTION:
Do not re-drill the burner orifices. If the orifice
size must be changed, use only new orifices.
The firing rate must be verified for each installation to
prevent over-firing of the unit. The firing rate must not
exceed the rate shown on the unit data label. To
determine the firing rate, follow the steps below:
1. Obtain the gas heating value (HHV) from the gas supplier.
2. Shut off all other gas fired appliances.
3. Start the unit in heating mode and allow it to run for at
least 3 minutes.
4. Measure the time (in seconds) required for the gas meter
to complete one revolution.
5. Convert the time per revolution to cubic feet of gas per
hour using Table 10 (page 24).
6. Multiply the gas flow rate in cubic feet per hour by the
heating value of the gas in Btu per cubic foot to obtain
the firing rate in Btu per hour. See Example.
Example:
• Time for 1 revolution of a gas meter with a 1 cubic
foot dial = 40 seconds.
• From Table 10, read 90 cubic feet gas per hour.
• 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.
7. Adjust the manifold pressure if necessary. See Manifold
Pressure Adjustment above. For additional information
about elevations above 2,000 feet, see page 14.
Manifold Pressure Adjustment
The manifold pressure must be set to the appropriate
value for your installation. To adjust the manifold pressure:
1. Obtain the required manifold pressure setting. Use Table
4 (page 15) for natural gas or Table 5 for LP/propane
gas.
NOTE: The values listed in the tables are based on
sea level values. At higher altitudes, the heating value
of gas is lower than the sea level heating value.
2. Remove the regulator capscrew (Figure 8) from the
INLET side of the regulator.
3. 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.
4. Replace and tighten the regulator capscrew over the
adjustment screw.
Capscrew
Inlet
Pressure
Tap
Figure 8. Regulator Capscrew & Tap Locations
Verifying Over-Temperature Limit Control
Operation
1. Verify the louvered control access panel is in place and
that there is power to the unit.
2. Block the return airflow to the unit by installing a close-
off plate in place of or upstream of the filter.
3. Set the thermostat above room temperature and verify
the units operating sequence (pages 18 - 19).
NOTE: The over-temperature limit control should turn off
the gas valve within approximately four minutes (exact time
depends on the efficiency of the close-off when blocking
the return air). The circulating air and combustion blowers
should continue to run when the over-temperature limit
control switch opens.
4. Remove the close-off plate immediately after the over-
temperature limit control opens. If the unit operates
for more than four minutes with no return air, set the
thermostat below room temperature, shut off power to
the unit, and replace the over-temperature limit control.
Manifold
Pressure
Tap
17
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