Supply air maximum relative humidity limitation

To prevent the risk of wet ducts, the relative humidity is limited to a value, defined by parameter SAH-01. Depending on the maximum relative humidity setpoint and the P-band SAH-02 the internal maximum relative humidity control signal varies from 0 to 100%, as shown in the next figure.



A plausibility check is executed on the input "MaxHygrostat", which means that only in case of humidifying the "MaxHygrostat" input is monitored. When the maximum discharge air limit "MaxHygrostat" becomes true (= 1), it will override the room relative humidity control and generate an alarm at the output datapoint “HighHumAlarm”.


Description

Default value

SAH-01: max. setpoint supply air relative humidity

90 %RH

SAH-02: P-band maximum setpoint control

12 %RH



Humidity high alarm

The output datapoint “HighHumAlarm” generates an alarm when during humidification the relative humidity in the duct has exceeded the level as defined by the maximum hygrostat "MaxHygrostat".

During de-humidification the maximum hygrostat can cause an alarm because of the high relative humidity in the supply duct. In this case the datapoint “HighHumAlarm” will not generate an alarm.

In case of alarm, the humidification control signal is set to 0% and the output "HumidEnable" is set to off.


The alarm will be reset automatically  as soon as the "HighHumAlarm" input returns to normal.