Reznor PDF2SF Unit Installation Manual - Manual (Page 19)

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NOTE: If thermostat differential is set too high the gas
heat system may energize (depending on thermostat
model) and de-energize the heat pump outdoor system.
Gas heat will remain in operation until the thermostat
call for heat is satisfied.
4. Allow the heating system to operate for several minutes
and then set the temperature selector below room
temperature. Verify the system shutdown sequence.
Note: The blower will remain operating for 60 or 150
seconds after the call for heat is removed depending
on if the system was in heat pump or gas heat mode,
respectively, unless the thermostat switch is set to the
ON position.
Gas Heating (Emergency Heat Mode)
NOTE: When thermostat is set to the emergency heat
position, heat pump operation will be locked out.
1. Set the thermostat to the lowest setting.
2. Follow the procedures given on the gas operating
instruction label, in this installation instructions or
attached inside the louvered control access panel.
3. Set the thermostat one degree above room temperature
and verify the sequence of operation. See Operating
Sequence section (page 21.)
4. Verify that the compressor and outdoor fan motor are
not energized.
5. After determining the system is operating properly, wait
1-2 minutes and then raise the thermostat temperature
set point an additional 1-2 degrees until the heating
system moves into 2nd stage or high heat operating
mode. The gas valve will energize to high heat mode
while the induced draft motor and indoor blower motor
both increase in speed.
6. After the unit has run for approximately five minutes,
set the thermostat below room temperature. Verify the
shutdown sequence; steps 10 -12 in the Operating
Sequence section (page 22).
Verifying & Adjusting Temperature Rise
Verify the temperature rise through the unit is within the
range specified on the unit data label for both high and
low firing rates. Temperature rises outside the specified
range could result in premature heat exchanger failure.
1. Place thermometers in the return and supply air stream
as close to the unit as possible. The thermometer on the
supply air side must be shielded against direct radiation
from the heat exchanger to avoid false readings.
2. Adjust all registers and duct dampers to the desired
position. Run the unit for 10 to 15 minutes before
taking any temperature readings. The temperature
rise is the difference between the supply and return air
temperatures.
NOTE: For typical duct systems, the temperature rise will
fall within the range specified on the data label (with the
blower speed at the factory recommended setting) shown
in Table 9 (page 27). If the measured temperature rise falls
outside the specified range, it may be necessary to change
the blower speed. Lowering the blower speed increases
the temperature rise and a higher speed decreases the
temperature rise.
The unit is equipped with a variable speed motor. Heating
and cooling speed selection is made by changing the tap
settings on the ignition control board located in the unit
control box. Refer to Configuring the Variable Speed Blower
Section (page 12) for additional information.
The Variable Speed Blower (VSB) is designed with built
in delay profiles for start up and shut down of the system.
Refer to the Operating Sequence section (page 21) for
more details.
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 furnace.
The firing rate must
not exceed the rate shown on the unit data label.
To
determine the firing rate, follow these steps:
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 14 (page 28).
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.
7. Adjust the manifold pressure if necessary. See Manifold
Pressure Adjustment instructions on page 20. For
additional information about elevations above 2,000
feet, see page 17.
Example:
• Time for 1 revolution of a gas meter with a 1 cubic
foot dial = 40 seconds.
• From Table 14, 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.
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 (page 21).