Reznor PDF2SF Unit Installation Manual - Manual (Page 12)

12
Heating Configuration
This furnace is factory configured for two stage heat pump
operation and as a 2 stage gas heating system when the
thermostat is set to the Emergency Heat position.
Heat Pump Defrost Mode
The Ignition/Blower Control board has an Automatic
Heat Staging jumper which can be repositioned to bring
on the second stage of gas heat after a pre-determined
delay in minutes that can be used to offset any cool air
while the unit may be in a prolonged defrost cycle. This
feature should only be used in applications where extreme
outdoor coil icing may occur. Reposition the automatic heat
staging jumper from factory setting “NONE” to 5 or 10 for
the desired delay in minutes before the gas furnace will
automatically move to high heat operation. See Figure
12B (page 30).
Checking Heat Anticipator Settings
• Add the current draw of the system components.
OR
• Measure the current flow on the thermostat R-W
circuit after the circulating blower motor has started.
Set the heat anticipator according to the thermostat
manufacturer’s instructions for heat anticipator settings.
Configuring the Variable Speed blower
The variable speed blower has been designed to give
the installer maximum flexibility for optimizing system
performance, efficiency, and comfort. It is equipped with
a microprocessor-controlled variable speed motor that is
pre-programmed to deliver optimum airflow in a variety of
conditions and system configurations. Because the blower
can be configured in many ways, it is important to read
and follow all instructions carefully.
CAUTION:
To avoid personal injury or property damage,
make certain that the motor leads cannot
come into contact with any uninsulated metal
components of the unit.
Before operation, the variable speed blower must be
configured to match the unit with the system, climatic
conditions, and other system options. With the blower
installed and configured properly, the furnace will gradually
change speed in response to changes in system variables
such as thermostat settings, duct static, filters, etc. The
variable speed blower is configured by setting the heat,
cool, and adjust jumpers located on the ignition control
board as described below. See Figure 12B (page 30).
Selecting Cooling Airflow
The cooling airflow is selected by setting the Cool and
Adjust jumpers on the ignition control board. Table 11
(page 27) lists the recommended airflow values (CFM) and
selector tap settings for each nominal system capacity. All
airflows for other modes of operation (except secondary
gas heat) are determined by this basic setting. For
maximum capacity, generally, a selection at or near the
top of the CFM range for that nominal capacity is best.
NOTES:
• The CFM values listed in Table 11 are not dependent
on duct static pressure. The motor automatically
compensates (within the limits of the motor) for changes
in duct static pressure.
• If coil icing occurs, the basic cooling airflow selected
may be too low. Verify the selected setting is within the
range shown in Table 11 and the system is properly
charged. If icing continues, raise the selected airflow
to the next higher tap.
• For maximum dehumidification and energy efficiency,
select an airflow near the middle or bottom of the CFM
range for that nominal capacity.
• The 2-stage cooling feature of the unit requires
modulating the airflow. The unit will automatically adjust
the airflow to the appropriate rate when the unit capacity
changes.
Selecting Gas Heating Airflow
The heating airflow is selected by setting the heat jumper
to the desired tap (A,B,C, or D) located on the ignition
control board. Refer to Table 12 (page 27) and select a
nominal rise based on the furnace’s nominal efficiency
and firing input. Follow across the table row to find the
tap setting and nominal air-flow. Verify the selected rise is
within the specification shown on the furnace rating label.
Table 4. Thermostat Wire gauge
Thermostat
Wire gauge
Recommended T-Stat Wire
Length (Unit to T-Stat)
2-Wire
(Heating)
5-Wire
(Heating/Cooling)
24 55 25
22 90 45
20 140 70
18 225 110
COPPER WIRE SIZE — AWG
(1% Voltage Drop)
Supply Wire Length-Feet Supply Circuit
Ampacity
200 150 100 50
6 8 10 14 15
4 6 8 12 20
4 6 8 10 25
4 4 6 10 30
3 4 6 8 35
3 4 6 8 40
2 3 4 6 45
2 3 4 6 50
2 3 4 6 55
1 2 3 4 60
Wire Size based on N.E.C. for 60° type copper conductors.
Table 3. Copper Wire Size