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Old 03-04-18, 10:25 AM   #5
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Originally Posted by HugoW View Post
Thanks! I bought it for 25,-. I will source such an inverter probably from Aliexpress, I cannot find any second hand ones. Next on my list of stuff I need to figure out is the required expansion valve. My plan is to use CO2 as refrigerant, but Ali does not have any valves specifically for that purpose. None that I can find, anyway. The search continues, info welcome!

Cheers, Hugo
Hello Hugo!

In my opinion, using CO2 which is environmentally friendly, and efficient, may not be a good choice for your project. CO2 has extremely high workng pressure, and requires very hard to find heat exchangers, and compressors, etc.

For any DIY project I reccommend a lower pressure refrigerant such as R134A or something similar. If you take a good look around Ecorenovator, you will see that many people are using R290 as a refrigerant. It is low pressure, efficient, and the cost is very low. It does have the hazard of being highly flammable. There are ways to configure your system to avoid the possibility of a R290 leak inside a house, or it is possible to build in a sensor + exhaust blower in case of a R290 leak.

Your drawing appears to have a pump to circulate refrigerant to the expansion valve and HX (Heat Exchanger). Do you intend for the pump symbol to be the compressor??

I think your dual HX setup is overly complex. You should have a single HX heating a water tank and swith water, in my opinion. I f you want domestic hot water from that tank, run tank water through a HX.

Your heat pump should be heating a water tank that holds the higher temp water that you will need, if it is heating water, that is what your tank should be. If it is domestic water, then that is what it should be.

Best of luck.

I'm not an HVAC technician. In fact, I'm barely even a hacker...
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