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Old 09-25-17, 02:59 PM   #31
ecomodded
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If after reading the previous post if you still don't have a understanding of how this could work read Jeff's #15 post again.

It helped me to understand that the theory that it works is actually a fact.

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Originally Posted by jeff5may View Post
Ok, here's my take on what you're figuring. The compressor uses maybe 1000 Watts up from the power line. Some of this is radiated from the compressor shell directly and some superheat is added to the cool refrigerant as it passes by the motor coils. The rest is used up as work of compression. As the preheated and compressed refrigerant condenses, all of the added superheat is dissipated before the gas condenses. So there's your standard resistance heating component. The fans don't count, as they are not using lots of power, and are either both adding to indoor heating or subtracting heat from each other.

As the refrigerant condenses, it gives off lots of heat. It is then subcooled a few degrees. Due to the high surface area and high airflow, heat recovery is effective. Lets say that x amount of airflow heats up 9 degrees F in one pass through the condenser. The warm air rises naturally away from the unit. Between the compressor radiation and forced air convection, there's your 14K BTU of raw heat gain.

On the other side, the room air is sucked through the evaporator at a slower rate and is cooled by the evaporating refrigerant. Let's say that x/3 amount of airflow is cooled 30 degrees F. This cold air is exhausted outside. Let's say 12K BTU makes it outside. So you lost 2K BTU in leakage between everything everywhere. That's 12K BTU NET HEAT GAIN.

This arrangement works well because the x/3 amount of infiltration (make-up) air is not always as cold as the exhaust air, especially in spring and fall. When it is warmer outside than your exhaust air, let's say 35-40 degrees F, the system is gaining BTU from your make-up air. With a 1-pipe setup, the delta T is always going to be low, as both heat exchangers are being fed room temperature air. As a result, the evaporator is not going to frost up on you (more latent energy rejection down the drain as condensed humidity), and the unit COP remains high. Even when it is frosty outside, the recirculated BTU (drawn into the refrigerant in the evaporator and rejected into the house) is much more than the power drawn from the power line. The gradients from (the make-up air minus exhaust air) and (outdoor air minus exhaust air) subtract from the overall refrigerant heat transfer.

With a 2-pipe setup, the evaporator is fed cold outdoor air. The delta T works against outdoor temperature, and so does COP and condenser discharge temperature: as outdoor temperature drops, they all get worse. As outdoor temperature approaches freezing, the evaporator can frost up fast, then the unit loses its advantage. Efficiency really depends on lots of stuff that is usually not included in these rigs, like variable expansion valves and hot gas defrost. That's why the makers discourage 2-pipe use below about 40 degrees F: passive defrost using ambient airflow to thaw out the evaporator is slow, plus the compressor is shut off.

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Old 09-25-17, 03:40 PM   #32
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Sorry my understanding of heatpumps does not allow for heat to be created from nothing.

Please don't waste any money on this.

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Old 09-25-17, 04:14 PM   #33
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Please enlighten us with your understanding of heat pumps particularly the refrigeration cycle.
I love learning its my favorite past time
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Old 09-25-17, 04:24 PM   #34
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Quote:
Originally Posted by ecomodded View Post
Please enlighten us with your understanding of heat pumps
I love learning its my favorite past time
It's in the name "Heat Pump" it pumps heat from one place to another.

A GSHP pumps heat out of the ground into the house.
A ASHP pumps heat out of the external air and into the the house.
A Fridge or freezer pumps heat from inside the appliance to the radiator on the back.

Your idea involves pumping heat from inside your house to inside your house
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Old 09-25-17, 04:39 PM   #35
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O.k So I can deduce from your answer that you are not familiar with the Refrigeration cycle. Until you delve into it on your own and teach yourself how it works you will be ignorant as to how the COP is made
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Old 09-25-17, 05:07 PM   #36
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Jeff's explanation explains pretty elegantly and clearly and his numbers are damn close

The 14000 BTU ac I picked up makes only 11,000 Btu in heat 14,000 in cool mode.

The loss Jeff explained in his post (his estimate was 12,000 Btu ) account for the lower heating efficiency of the unit in heat mode same as the manufacture claims.

Jeff5may knows his refrigeration , I mean did you get what he said ? Its real information that accounts for the 2.7 COP

That 2.7 Cop turns 1200 watt input power into 3240 watts of heat energy.

Hence the gains from "nowhere"
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Old 09-25-17, 05:54 PM   #37
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How I got the COP number of the portable ac heat pump

Rated input power 1200 watt
Rated Btu (heat) 11,000 Btu

1200 watt to Btu = 4095 Btu

Divide 4095 Btu into 11,000 Btu = COP

11,000 Btu divided by 4095 Btu = 2.68 COP

The unit will more then likely draw 1150 to 1175 watts pushing the COP up past 2.7

1150w draw puts the COP at 2.8
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Old 09-25-17, 07:56 PM   #38
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With this indoor heat pump I should buy a cheap HRV / heat recovery vent and put it in the same room as the AC.

It would work great with this pump , it could be wired off the Ac's fan power line to run at the same time. Im going to scout one out right now.

I love that idea

edit - They are too costly new about $750 to $1000
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Old 09-25-17, 08:16 PM   #39
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Quote:
Originally Posted by Ormston View Post
Your idea involves pumping heat from inside your house to inside your house
Still a net gain if you take from where it's not needed and send it to where it is needed.
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Old 09-25-17, 08:32 PM   #40
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To clarify it makes heat and rejects cold

It doesn't just move it around that would be a Vent its more complex then a Vent.

That pesky 2.7 COP has to come from somewhere and its the refrigeration process and Enthalpy.

You will get it

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