Hissing ASHP

Recently my ASHP has started to hiss when it starts up and expels warm moist air (my glasses steamed up) before running cold after a few minutes.

I've never noticed it hiss or expel warm air - is this normal or is something going wrong with the heat pump?

Assuming you are standing in front of the outdoor unit then it sounds like it is going through a defrost period.

Further assuming that it is still providing hot water and heating as desired then this is perfectly normal.

:cool:

Thanks Viking - that's a relief!