Heat pump efficiency

I live in the Montreal area. I just bought a York Affinity heat pump with R-410A. I don't understand why at outside temp around freezing point, the efficiency seems to be pretty low (gaz tubing temp at the input of the indoor coil barely warm to the touch) At lower outside temp., it is much hotter, so I suppose the efficiency to be better. It doesn't make sense to me. Moreover, outside humidity seems to have an effect too. Can someone explain if such a condition is possible and why.
Thanks,
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Heat pumps don't work as well at lower temperatures because there is less heat to remove from the air. What you are describing could be due to an electric backup (most have an electric resistance heater to help when the outside temperature is too low). Humidity would have an effect as well. Lower temperatures + higher humidity might cause the outdoor coils to ice more quickly, requiring the electrical backup to kick on and the defrost cycle to run.
Don't mistake more heat with more efficiency, it's probably much less efficient when this happens: the defrost cycle is reversed from heat pump cycle and is running like an AC compressor - the electric heat strip has to heat your house AND the outdoor coils to defrost them.
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snipped-for-privacy@videotron.ca wrote:

What is happening is the backup resistance heat is kicking in. That happens when the low temperatures approach the point where the heat pump is less efficient (it gets less efficient as it gets colder) than resistance heat. Sorry to tell you this but when that happens it may put put more heat, but it is using even more electricity. It is really costing you more.
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Joseph Meehan

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Your heat pump is basically a refrigerator for the outside; it cools the outside and puts the heat inside. Efficiency is a function of the temperature difference between the two area; it is simply easier to move heat from a 10C outside to a 20C inside than it is to move heat from a -10C outside to a 20C inside. Efficiency goes to hell when temperatures drop. So, roundabout 5C the heat pump turns off and a backup heat turns on. Hopefully that is a gas furnace, but it can be electric heat.
As someone else said, when it gets colder you are feeling the heat from the supplemental source; it is typically much hotter than the heat pump because it has to have the capacity to heat your house in really cold weather.. Heat pumps really only make sense in warmer areas where it rately gets below freezing. (or where electricity is artificially cheap for some reason) In Montreal you will be using nothing but the supplemental heat for almost the entire winter. I just replace my heat pump with a regular AC and a furnace for that reason; none of people quoting on the job even asked about putting in a new heat pump.
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York Affinity may be a two speed system. Down to about 35 degrees outside would be low speed, below that it will go into high speed and the gas line will get warmer untill it gets MUCH colder outside. Im not a Yyork dealer so I am just guessing on the details. Check the York site for more information.
I love heat pumps in my area, but i would not use them in your climate.
Stretch
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