On Mon, 28 May 2012 20:30:47 +0100, Andy Champ wrote:

The limiting factor on air source systems is condensation - if the cold
end is below the dew point you get condensation.

Assuming there is any moisture in the air to condense. Condensation
isn't a great problem as it will drain away.

If it's also below freezing you get ice.

Air temp below freezing or evaporator below freezing? If the air temp
is below freezing there won't be any significant moisture present to
condense and form ice. So air source heat pumps work well with air
temps from 0C down to around -10C. They struggle, due to icing and
having to defrost, with air temps between 0 and about 5C.

--
Cheers
Dave.