Reznor UDAS Unit Installation Manual - Manual (Page 21)

Page 21
8.0 Controls and
Operation
8.1 Thermostat
Use either an optional thermostat available with the heater or a field-supplied 24-volt
thermostat. Install according to the thermostat manufacturer’s instructions, paying par-
ticular attention to the requirements regarding the location of the thermostat.
Make sure that if there is a heat anticipator setting on the thermostat, it is set at 0.6 amps
(or in accordance with the amperage value noted on the heater wiring diagram).
Make thermostat connections at the terminal strip on the back of the heater. The strip
has four terminals, R, G, W1, and W2; refer to the wiring diagram.
IMPORTANT: All units MUST be operated by a 24-volt thermostat. Never use a
line voltage disconnect switch as a means of operating the heater. Operating Model
Sizes 30-125 by means other than a 24-volt thermostat may result in the flame rollout
switch tripping.
Multiple Heater Control, Option CL31 and Option CL32
-
If the heater was ordered
with a multiple heater control option, one thermostat can be used to control up to six
heaters. The option includes a 40VA transformer that replaces the standard trans-
former in the “controlling” unit and a relay assembly that attaches to the additional
unit. Option CL31 provides for control of two heaters. If control of additional heaters is
desired (up to six total), Option CL32 which is the relay assembly only must be added
to each additional heater.
The option packages are shipped separately and include complete instructions on
installation and wiring.
Sizes 30-125 are equipped with a temperature activated manually reset flame rollout
switch. The flame rollout switch is located at the top of the burner assembly. It is fac-
tory set and is non-adjustable. If the setpoint is reached, the flame rollout acts to inter-
rupt the electric supply to the gas valve. If the flame rollout switch activates, identify
and correct the cause before resetting the switch. Refer to the Maintenance Section,
Paragraph 10.2.10, for information on probable causes and instructions on resetting
the flame rollout switch. (For location, see FIGURE 18, page 30.)
DANGER
If the manual reset flame rollout switch activates, identify and
correct the cause before resetting the switch. Never bypass the
flame rollout switch; hazardous conditions could result. See
Hazard Intensity Levels, page 2.
7.5.3 Door Switch
for Separated
Combustion Models
only
All sizes of Separated Combustion Model heaters are equipped with a door switch
which prevents the heater from operating when the service door panel is open. The
service panel of a Separated Combustion Models are equipped with a pliable gasket
material that fully seals the door to provide added protection from building air entering
the combustion zone of the heater. (For switch location, see FIGURE 18, page 30.)
The main operating gas valve is powered by the 24-volt control circuit through the ther-
mostat and safety controls. The main control valve is of the diaphragm type providing
regulated gas flow preset at the factory. (For location, see FIGURE 18, page 30.)
WARNING
The operating valve is the prime safety shutoff. All gas supply
lines must be free of dirt or scale before connecting the unit to
ensure positive closure. See Hazard Levels, page 2.
7.5.4 Gas Valve
7.5.5 Fan Motor The fan motor is equipped with thermal overload protection of the automatic reset type.
Should the motor refuse to run, it may be because of improper current characteristics.
Make certain that the correct voltage is available at the motor.
NOTE: If the unit is equipped with an optional totally enclosed motor or optional volt-
age, the horsepower may be larger than the standard motor. Refer to the motor name-
plate to verify horsepower.
7.5.6 Venter Motor
The venter motor is assembled to the venter wheel and operates to provide combus-
tion airflow. Operation is controlled by the ignition control module (circuit board); refer
to ignition system in Paragraph 8.3.