Enthalpy-Based Free Cooling And Free Heating - Daikin UATYA-B Operation Manual

3.13.8 Enthalpy-based free cooling and free heating

Free cooling and free heating in systems where the controller manages both temperature and humidity may be run by com-
paring the room enthalpy and the external air enthalpy.
This function is enabled using parameter "DA5": the activation differential is set in parameter "DA7".
The controller takes the enthalpy setpoints in cooling and heating mode from the corresponding temperature and humidity
setpoints and it takes the room enthalpy and external air enthalpy values from the corresponding temperature and humidity
probes.
The comparison of the enthalpy values taken from the setpoints and the values from the probes helps check three condi-
tions required for cooling and heating:
the external air enthalpy "h_ex" is higher than the room enthalpy "h_en", which in turn is higher than enthalpy setpoint
"h_set" during operation in cooling mode; or the external air enthalpy "h_ex" is lower than the room enthalpy "h_en", which
in turn is lower than the enthalpy setpoint "h_set" during operation in heating mode. Enthalpy-based free cooling or free
heating is not advantageous in these cases;
h_set
the room enthalpy "h_en" is higher than the external air enthalpy "h_ex", which in turn is higher than enthalpy setpoint "h_set"
during operation in cooling mode; or the room enthalpy "h_en" is lower than the external air enthalpy "h_ex", which in turn
is lower than the enthalpy setpoint "h_set" during operation in heating mode. Enthalpy-based free cooling is advantageous
in these cases when the difference between the measured enthalpy values is greater than the setpoint in parameter "DA7".
Free cooling is active for as long as the room enthalpy value "h_en" equals the external air enthalpy value "h_ex", increased
(first case) and reduced (second case) by the differential value set in parameter "DA7";
h_set
the room enthalpy "h_en" is higher than the enthalpy setpoint "h_set" for operation in cooling mode, which in turn is higher
than the external air enthalpy "h_ex"; or the room enthalpy "h_en" is lower than the enthalpy setpoint "h_set" for operation
in heating mode, which in turn is lower than the external air enthalpy "h_ex". Enthalpy-based free cooling is advantageous
in the first case, whereas enthalpy-based free heating is advantageous in the second case.
h_ex
Damper opening may be limited with respect to the max. value set in parameter "DA13" as a result of problems with tempe-
rature or pressure, as described in the chapter on limitations.
Daikin R32 Rooftops UATYA-B
ESIE21-02 – 2021.03
Free cooling
h_en h_ex h (kJ/kg)
Free cooling
h_ex h_en h (kJ/kg)
Free cooling
h_set h_en h (kJ/kg)
Free heating
h_ex h_en h_set
Free heating
h_en h_ex h_set
Free heating
h_en h_ex
h_set
3 Software functions
h (kJ/kg)
h (kJ/kg)
h (kJ/kg)
Service manual
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