Reznor CAUA Users Manual - Manual (Page 13)

Form O-CAUA, P/N 164772 R7, Page 13
Modulating
Damper Motor,
P/N 196302 with
Logic Module
Modulating Damper Motor with Logic Module
Function: The modulating damper motor actuates the dampers in
response to enthalpy controls for cooling or a mixed air controller for
heating. Outside air dampers close when the heater shuts down.
Service: There is no service required other than external cleaning. If
the motor or module needs replaced, replace with identical parts.
Potentiometer
Potentiometer
Function: The potentiometer is a manually set switch used with modulating dampers
to set a minimum outside air damper opening. It is either mounted in the mixing box or
remotely located.
Service: If the potentiometer needs replaced, replace it with an identical switch.
Return Air Controller
Function: The return air controller senses the temperature of the incoming return
air. On a two-position outside air damper system, it activates the motor to open and
close the outside air damper. On a modulating system, the return air controller main-
tains 100% return air until the set temperature is reached at which point the mixed air
controller (with or without potentiometer) controls the dampers based on the mixed air
control setting. When in the heating mode, the temperature of the "mixed" return and
outside air entering a standard Model CAUA heater must always be 35°F or above.
Only when the heater is factory equipped with makeup air Option AD4 can the entering
air temperature be below 35°F.
Service: If the controller needs replaced, replace it with an identical control.
Mixed Air Controller
Function: The mixed air controller senses the temperature of the air entering the
heater. It automatically operates the damper motor to modulate the outside and return
air dampers based on the temperature setting. When in the heating mode, the tem-
perature of the "mixed" return and outside air entering a standard Model CAUA heater
must always be 35°F or above. Only when the heater is factory equipped with makeup
air Option AD4 can the entering air temperature be below 35°F.
Service: If the controller does not function properly, replace it with an identical control.
Return Air
Controller
Mixed Air
Controller
2-Position
Enthalpy
Control
Modulating Enthalpy
Sensor and Thermistor
Sensor
Enthalpy Sensor for 2-Position Control
Function: The enthalpy control senses the enthalpy (heat content in a lb of air) of
the outside air entering the heater. When the enthalpy is low, the control activates the
motor to open the outside air damper; when high, it closes the outside air damper.
Service: If the controller does not function properly, replace it with an identical control.
Enthalpy Sensors for Modulating Control
Function: There are two enthalpy sensors, one for outside air and one for return air.
Input from the two enthalpy sensors and the thermistor sensor to the logic module on
the motor allow the motor to modulate the dampers to maintain the set temperature
and control the moisture of the air entering the heater.
Service: If the controls do not function properly, replace with an identical control.
TABLE 5 - Application
of Inlet Air Damper
Controls by Option
Codes (page 14)
IMPORTANT NOTE: The standard Model CAUA is designed for a maximum tempera-
ture rise of 75°F. Above 35°F (2°C) outside air temperature, any percentage of outside
air is permitted. For optimum operation and to prevent condensation, the mixed air
temperature going to the heat exchanger must not be below 35°F (2°C).
The inlet air temperature restriction does not apply to a Model CAUA ordered with
makeup air Option AD4. A CAUA unit equipped with makeup air Option AD4 includes
stainless steel components and a flue wrapper condensate drain to permit inlet air
temperature below 35°F (2°C).