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DN-Series Integrated Programmable Controls
DOAS
66
6.6 ECONOMIZER CONTROL (BYPASS/FREE COOLING)
All DN DOAS units are equipped with a bypass damper which will make the incoming air bypass
the enthalpic plate. In this case, when the unit is in cooling or dehumidification mode, if the
OA is more favorable for cooling than the RA, the bypass damper will modulate to maintain the
cooling setpoint. Only when the damper is wide open at 100% will the cooling be allowed to
turn on.
The economizer settings are:
u
Temperature
u
Enthalpy
u
Disabled
Economizer based on Temperature Sequence:
When the OA temperature is below the RA temperature less the hysteresis value, the
economizer will modulate the face and bypass dampers using PI control to maintain the CA air
temperature (or RA temperature, based on setting). The KP and Ti can be adjusted to fine tune
the control.
The economizer will be locked out when:
u
The OA temperature is less than the economizer adjustable low lockout.
u
The RA temperature is below the adjustable low lockout
u
Heating is enabled
Economizer based on Enthalpy Sequence:
When the OA enthalpy is below the RA enthalpy less the hysteresis value, the economizer will
modulate the face and bypass dampers using PI control to maintain the CA temperature (or RA
temperature, based on setting). The KP and Ti can be adjusted to fine tune the control
The economizer will be locked out when:
u
The OA temperature is less than the economizer adjustable low lockout.
u
The RA temperature is below the adjustable low lockout
u
Heating is enabled
TEMPERING CONTROL
