Would I be correct in thinking that at temperatures of minus 10 -11C these air heat systems become ineffective? We have air source heating at home and if the temperature dropped below minus 11C no heating. I appreciate that it is not very often in the UK temperatures drop down to minus 11C or more, but if ou factor in the wind chill there may be the possibility.
We also have the issue of the system icing over at temperatures of zero, it then has to defrost itself to become effective again and to defrost requires energy.
Do you have any idea how they get around extreme cold temperatures?
Air source heating does become less effective as the ambient air temperatures fall, but the precise point at which they would stop working is dependant on the design of the system and the refrigerant used in it.
At sub freezing temperatures there is a probability the external evaporator coil can begin to ice up, and it will need to be defrosted from time to time. That will require some input of energy to achieve it, but how much again depends on the design and the conditions at the time.
However as the prime reason for air source heating is to take low grade heat from the large volume of air passing through the evaporator and to turn it into higher grade heat in the condenser coil, the system has already created savings of both energy and cost of energy. The defrost systems usually reverses the thermal ladder and will use some of the low cost heat it has already produced to defrost the external coil. This does have the effect of lowering the overall energy efficiency of teh system but usually it is still a net benefit.
Wind chill is often misunderstood. When you watch the weather forecast the reporter will sometimes say temperature will be 3C but becasue of the wind it will
feel more like freezing due to the wind chill .
The temperature of the air has not changed, what changes is the amount of heat stripped away from our skin because a greater quantity of air comes into contact and draws more heat energy away from us. Its the sensation of loosing more heat which makes feel it might be cooler than it actually is.
In terms of air source heating, having a wind presenting more air volume to the evaporator coil is actually a good thing as it is offering up the potential for more heat recovery.
How effective air sourced heating is does depend on the prevailing environmental conditions and thus it may be better suited to some climates than others.