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Old 01-29-18, 08:33 AM   #1
Lurking Renovator
Join Date: Jan 2018
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Default My DIY heatpump attempt

Hi all,congratulations for the great forum first

In general I'm experimenting with an old split air conditioner which i would turn in to some kind of homemade heat-pump.The basic idea is to replace the indoor unit with some kind of heat exchanger so the AC heats up water instead of air ,which in turn circulates over radiators in house-some kind of central air conditioning.
Since I'm not a HVAC or AC guy by occupation (I'm an electrician),but it's just my hobby,like electronics,i need some help and advices.

I'll try to explain what i have done so far,and what are my concerns and thoughts about the next steps.I forgot to mention that since that is still just a project with unknown result,i don't want to invest much funds in it,and installation i made it's just for testing,that's why it's not so good-looking

So the AC unit is a split type,12000BTU,DC Inverter,running on R410A.It's model is HAIER HSU-12HD03/R2(DB).My first idea was to buy a refrigerant to water heat exchanger,but it turned out,that R401A heat exchangers are way too expensive.For reference-new AC of this make and model costs about 250$,the heat exchanger costs nearly 220$,and the minimal salary in my country is about 230$...So it's not an option.The next idea which popped-up in my head was to use a container full of water in which i will wound a copper tube coil for the refrigerant.A friend of mine gave me an rusty old 60 liter water tank,which is just fine for that purpose.As "side" effect it will work as buffer,for the days when not all energy of the AC is required to heat the house-the AC heats up the tank to the specified temperature,and stops,and when the temperature of the tanks drop to some level,it turns on again,instead of running all the time.

The next question was-how much copper tube is needed for the coil?
Looking at some Danfoss and KAORI heat echangers on the web,for non R410A exchangers,about 12000BTU,the surface is about 0.3m2,and for R410A exchanger,slightly more,but about that value.
The original AC indoor's unit tubing was 7mm diameter,so the next bigger standard copper tube is 8mm diam with 1mm thick wall. I bought 8m of that tube,which surface area is (2*pi*r)*l or S=6.28*0.004*8=0.2m2.
I know it's less than the original ones,but my idea was to get higher discharge temp/water temp respectively.It should also rise the suction temp,which should make the outdoor unit build up frost more slowly or not?.I know it is at the cost of greater compressor working temperature,power consumption and wear,but if everything works fine,the tank will be from stainless steel and i'll put more copper tube inside.
Here are some pictures of the tank with the coil:

I'll continue in the next post,because this will become too long.

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