Pressure and AC/Heat Pumps

franco b
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Post By: franco b » Mon. Mar. 21, 2016 10:18 am

I agree that in the winter you would be using heat in the air you already paid to heat. Heated by coal though it still probably would be cheaper than electric. \

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Richard S.
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Post By: Richard S. » Mon. Mar. 21, 2016 10:31 am

franco b wrote:I agree that in the winter you would be using heat in the air you already paid to heat. Heated by coal though it still probably would be cheaper than electric. \
Cost is whole other topic. ;) At the end of the day directly heating with the same fuel as your primary is going to be the most efficient if you are using heated air. I'm just trying to understand how inefficient this would be.

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Post By: McGiever » Mon. Mar. 21, 2016 4:45 pm

Richard S. wrote:I'm just trying to understand how inefficient this would be.
The simple answer is that the HP water heater is moving/transferring heat from within the surrounding air/space and dumping it inside of the water filled heater tank. Now, every installed situation/or space will be different, depending on where that heat was sourced from.
Some heat in one installation is waste and in some other installations all heat is precious...and there is the big difference, unless we shall just ignore this aspect of the matter. 8-)
One size does NOT fit all. :roll:


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Richard S.
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Post By: Richard S. » Mon. Mar. 21, 2016 7:49 pm

McGiever wrote:
The simple answer is that the HP water heater is moving/transferring heat from within the surrounding air/space and dumping it inside of the water filled heater tank.


When you are using 2000 BTU's of heat sourced from your primary source this is inefficient. If you are losing most of that 1000 BTU's you used to extract it then it's a highly inefficient way to make hot water. That is what I'm trying to understand, is it merely inefficient or highly inefficient.

One thing that is clear is in warm weather and you want to remove heat from the room it's a highly efficient system and the other thing to consider is this acts as dehumidifier too.

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McGiever
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Post By: McGiever » Mon. Mar. 21, 2016 9:58 pm

There is a hands down better way to have your cake and eat it too...it's called a water to water heat pump...forget the air to water. :idea:

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Post By: Richard S. » Tue. Mar. 22, 2016 1:55 pm

McGiever wrote:There is a hands down better way to have your cake and eat it too...it's called a water to water heat pump...forget the air to water. :idea:
As far as I know the air sourced heat pumps for the water tank require a high ambient air temp around 55 degrees which is why they are not sourced from outside. I would assume they need the higher ambient temperature because it needs to do a lot more work to raise the water temperature above 120. The units for heating a house will work into the teens but they are only raising the air temperature a few degrees.

I would imagine using ground source would work since it will be in that 55 degree range but that is also going to work against you in the summer when you have a much higher ambient air temperature and you actually want to remove that heat from the home.

The ones for the tanks come with options for how they operate and one of those options is to just use standard electric. *Assuming you are losing the 1000 BTU's* during cold weather operation you can just switch it to standard electric. Other things to consider is dehumidifier action, depending on what that is costing you it may actually work out in the end.

*This is yet to be determined as I'm not sure where that 1000 BTU's of energy goes.


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Post By: McGiever » Tue. Mar. 22, 2016 9:23 pm

Richard S. wrote:I would imagine using ground source would work since it will be in that 55 degree range but that is also going to work against you in the summer when you have a much higher ambient air temperature and you actually want to remove that heat from the home.
Us ole coal burners are an ornery bunch. :) We never see a "half full glass"...it's always "half empty". ;)

But seriously, it is way better to both heat and cool your house working off of a constant 55*F medium.(regional ground source temp)
Beats trying to cool when the outside air temp is 90*F+ or heating when the outside air temp is -0*F those are pretty steep differentials. :roll:
Actually some of the ground source wasted summer heat gets recaptured for the early on heating and vise versa for the early on cooling.

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Post By: jpete » Sun. Jun. 05, 2016 7:56 pm

franco b wrote:The 1000 BTU is consumed in the conversion to mechanical energy by the compressor.
It wasn't "consumed", it was turned into rotational force and HEAT. That heat is also partially absorbed by the refrigerant. The rest goes off into the atmosphere.

In school those two things were called "heat of compression" and "heat of work". The work being the conversion of electricity to heat.

In a HP water heater, that heat goes into the water so it's not entirely "lost".

Also bear in mind that these units will also dehumidify the space somewhat if that is important to you.

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