Reznor RDF Unit Installation Manual - Manual (Page 19)

I-RDF, PN148384R5, Page 19
FIGURE 17 - Dirty
Filter Pressure Switch
Set screw
(on front of
switch) must
be manually
adjusted after
system is in
operation.
Negative pressure connection
is toward the "front or top" of
the switch (senses blower side
of filters)
Positive pressure connection is
toward the "back or rear" of the
switch (senses air inlet side of filters)
FIGURE 18 -
Discharge Sensor
and Mixing Tube
attach the negative pressure tube so that it will sense the pressure at the
blower side of the filter rack.
(NOTE: Tubing shipped is the same length for all sizes of systems; cut to the
appropriate length for the smaller systems.)
4) If required, cut the tubing to the proper lengths. Using the clamps provided,
attach the ends of the tubing to the filter rack at about center height being care-
ful not to kink or compress the tubing.
 After the system is operating, the filter switch must be manually set. With
clean filters in place, blower doors closed, and blower in operation, increase the
pressure setting by adjusting the set screw on the switch clockwise until the filter
light is energized or the screw is bottomed out. At that point, adjust the set screw
three full turns counterclockwise or until the screw is top ended. At that setpoint,
the filter light will be activated at approximately 50% filter blockage.
8.0 Controls Discharge Sensor (Maxitrol) for Gas Control Options AG30, AG31,
AG32, AG33, AG47, AG48 -
A discharge sensor may be shipped separately for
field installation. Attach the discharge sensor and mixing tube in the ductwork about six
feet (1.8 M) from the discharge opening of the system.
The sensor housing is not waterproof. If the installation is outdoors, field-fabricate a
waterproof protective enclosure for the discharge sensor, being careful not to affect its
air temperature sensing capability. If the ductwork is insulated, be sure that the sensing
bulb is mounted so that it is fully exposed to the airstream being sensed.
Refer to the wiring diagram and connect the sensor to the terminal strip in the blower
section electrical box. Use shielded wire to alleviate any electrical interference that
may cause an erroneous discharge temperature reading.
Outside Air Cutoff Control (Option BN2) -
After sensing pilot flame, the
burner ignites at its lowest input rate. The "amount of heat" required to reach the desired
discharge temperature also depends on the temperature of the incoming outside air.
The outside air cutoff (high ambient control) is factory set at 60°F (adjustable 25-
250°F). The burner reacts differently depending on the entering air temperature and
the setting on this control. The burner --
• may not ignite (pilot valve will not open);
If the actual temperature of the outside air is above the setpoint on the outside air
control, the burner will not ignite.
• may modulate to satisfy discharge setting;
• would shutdown completely only on Option BN2 control, once burner has been
fired; or
Modulating operation will depend on the temperature rise between the outside air
and the discharge air setting.
• may remain on continuous low fire.
If the outside air control is set too high, the burner will continuously burn on low fire
as long as the control switch is set to "winter".
When the outside air control is set properly for the climate, the system blower will con-
tinue to provide the required makeup air (ventilation) at the ambient outdoor tempera-
ture (burner not operating) even when the control switch is set to "winter".
If at startup, it is determined that the outside air cutoff control is not set properly,
change the setting on the control (located in the main electrical compartment) and test
for proper operation.
FIGURE 19 - Control
used for Outside Air
Cutoff and
Discharge
Temperature Low
Limit (Freezestat)