On May 25, 3:37*pm, wrote:
On Sat, 25 May 2013 10:14:31 -0400, wrote:
Why therefore shouldn't the evaporator in any heat pump ice up?

Perhaps because the evaporator doesn't get cold enough? You do know
that outdoor pools are used during the summer? *Speaking of dolt!

Harry lives in England
He is not sure what summer is.
That is why so many of his countrymen come here to Florida *;-)

If you are going to have a high coefficient of performance, the
evaporator will need to get cold.

http://en.wikipedia.org/wiki/Air_source_heat_pump#Usage
The outdoor section on some units may 'frost up' when there is
sufficient moisture in the air and outdoor temperature is between 0°C
and 5°C (32°F to 41°F)[citation needed]. This restricts air flow
across the outdoor coil. These units employ a defrost cycle where the
system switches temporarily to 'cooling' mode to move heat from the
home to the outdoor coil to melt the ice. This requires the
supplementary heater (resistance electric or gas) to activate. The
defrost cycle reduces the efficiency of the heat pump significantly,
although the newer (demand) systems are more intelligent and need to
defrost less. As temperatures drop below freezing the tendency for
frosting of the outdoor section decreases due to reduced humidity in
the air.