Daikin UATYA-B, Operation Manual

Page: 78 / 126

78
Service manual Daikin R32 Rooftops UATYA-B
ESIE21-02 – 2021.03
3.16.2 Post heating
When the value in parameter “STH55” is “1”, auxiliary heating is configured for summer operation only and serves as post
heating during dehumidification. The control can either be proportional or PID, depending on the value set in parameter
“STH57”. The value in parameter “STH56” identifies the probe taken as reference for the control which is performed accor -
ding to parameter “STH58”.
3.16.3 Single source for winter heating
When the value in parameter “STH55” is “2”, auxiliary heating is configured for activation in winter operation only.
If the unit is not fitted with a 4-way valve for cycle reversal - refrigerant circuit only used for cooling -, auxiliary heating is the
only source of heating in winter mode.
The control can either be proportional or PID, depending on the value set in parameter “STH91”. The value in parameter
“ST9” identifies the probe taken as reference for the control which is performed according to parameter “STH1”.
3.16.4 Auxiliary heating and heating by refrigerant circuit
When the value in parameter “STH55” is “2”, auxiliary heating is configured for activation in winter operation only.
If a 4-way valve is configured, the refrigerant circuit too can operate as heating source.
Each source is managed according to a dedicated control mode (either proportional or PID). The value in parameter “ST9”
identifies the probe taken as reference for the control which is performed according to parameter “STH1”.
The reference probe and the setpoint are common to both sources.
The activation of the two heating sources is prioritised according to the setpoint stored in parameter “STH129”, which may
be:
- “STH129” = 0 - heating by refrigerant circuit is prioritised over auxiliary heating;
- “STH129” = 1 - auxiliary heating is prioritised over heating by refrigerant circuit;
- “STH129” = 2 - both heating sources have the same priority. If the sources have the same priority, the controller uses
them together to manage the relevant demand.
3.16.4.1 Demand distribution with different priorities
If the two sources do not have the same priority, the controller fulfils the heating demand by starting the prioritised source
first and then the other.
The demand to the prioritised source can rise until the value stored in parameter “STH126”.
After the setpoint in parameter “STH126” is achieved, the controller stops the demand to the prioritised source and it starts
the second source, after the time set in parameter “STH127” has elapsed.
As soon as the second source reaches the setpoint in parameter “STH133”, for as long as the time in parameter “STH128”,
the controller starts increasing the demand to the prioritised source too.
A fixed demand may be set for auxiliary heating during the defrost cycle, equal to the setpoint in parameter
“STH132”.
3.16.5 Auxiliary heating in both winter and summer operation
When the value in parameter “STH55” is “3”, auxiliary heating is configured for both winter and summer operation.
The operating mode is as described in the above sections.
The air temperature in the return line determines the operating mode:
- if the air temperature in the return line is lower than the setpoint in parameter “STH1”, the unit operates in winter mode;
- if the value is higher than the setpoint in parameter “ST1”, the unit operates in summer mode.
3 Software functions