The efficiency of air conditioners and heat pumps can be significantly reduced by icing in cold and humid weather. Some units handle this with periodic defrost cycles, while others use built-in electric heaters. Both methods consume additional energy and reduce overall efficiency.
If another heat source is available, typically a gas-based heating source, the system can automatically switch to it when outdoor conditions approach the icing range. This can improve operational reliability and may reduce operating costs.
A simple solution would be to switch heat sources based only on outdoor temperature, for example below -5 °C. However, this is not always accurate because:
in humid weather, icing and defrosting may become significant even at relatively mild sub-zero temperatures;
in dry, cold weather, a heat pump may continue to operate efficiently at considerably lower outdoor temperatures.
Outdoor temperature and relative humidity together determine the dew point. This provides additional information about the moisture content of the air and therefore about conditions in which frost formation on the outdoor heat exchanger may become more likely.
DSVT_12 can therefore use the outdoor dew point as one of the conditions for switching operating modes. Compared with a fixed outdoor-temperature threshold, this can better reflect:
when icing conditions are becoming more likely,
when heat-pump efficiency may deteriorate because of frequent defrosting,
when it may be preferable to switch to another heat source.
The setting includes a freely adjustable compensation value, allowing the switching threshold to be adapted to the characteristics of the specific equipment, local conditions and operating experience.
The function can use:
data from a local outdoor temperature and humidity sensor, or
data based on the OMSZ AROME weather model (ipdns.hu registration required).
