York heat pump

Hi. I have a 1 year old York model B1HP036A06A heat pump that is not quite keeping up with the cold (for California) temps in the early morning hours. It is supplying a rebuilt 100 year old house of approx 1200 sq. ft.
What happens is it starts blowing cold air. When I turn it off for a few minutes, it comes back to life and works fine for a while, then it will do the same thing. This morning I looked at the outdoor unit and found a layer of frost coated the entire fin surfaces.
It got down to about 24 deg F last night.
I had a tech look at it last week and he fiddled with the thermostat, saying that it had been set to "fast" and reset it to "slow"; I'm not sure what that was, as I see no such settings on the setback thermostat. He serviced the unit and it seemed a bit better, until the cold (for us) hit again.
Any ideas? Is this normal behavior for the unit?
Thanks
bill
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[original post is likely clipped to save bandwidth]

It is well known that the heat pump function of air exchange heat pumps doesn't function well by itself as outside temperatures approach freezing. Thus, some provisions need to be made to handle such outside temperatures.
Have your tech explain how your system is designed to cope with near or below freezing temperatures and avoid frost build up that will block air flow and any possible heat "pumping". Some just have a simplistic back up electric heater, let the tech explain yours.
If a tech can't explain how your system is designed to accommodate low outside temperatures and convince you he tested those functions, get a different tech!
gerry
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wrote:

Frost build up can happen with its 50F out... The defrost board fixes that....

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CBHVAC wrote:

Not sure what you mean "with its 50F out". Is that a fuse or something, or are you referring to temperature or what?
thanks for all the answers so far.
bill
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Google is your friend
Notwithstanding, outdoors unit on heat pumps will freeze up under certain weather conditions, thus blocking airflow .....
So most units will have controls hardware installed that forces them into into a reverse cycle mode in order that mass airflow capacity through the outside coils can be regained--the outdoor fan will stop, yet the compressor and indoors unit still runs....most notably, very cold air will be typoically be felt coming from the inside supply registers if there is no active backup heat during defrost.
Now suggest post in alt.home repair if you have any more questions about this, usually plenty of folks there who will wish to explain this all in every minute detail.
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SVL



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Nice post Sam, up to the last sentence. Suggest you read the original intended FAQ.
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Thanks, Fish--I take my compliments where I can, and I do realize that one was sincere.
Also I am aware of the faq--just that seems answering the same questions in alt.hvac over and over appears to have become something many, if not most of the regular contributers there have grown tired of.
And so (notably), I have decided in the future to at least occasionally change the followup header to the home repair group and suggest they post there, if/when I myself have also grown tired, and whereupon few of the alt.hvac regulars are seemingly displaying much interest in continuing with addressing the OP 's original concerns.
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