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Old 03-01-18, 06:29 AM   #1
HugoW
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Default HugoW's very slow DIY air-to-water- heat pump build

Hello everybody,

I’ve been lurking here for a while, now I have registered because I have a question. I am planning to make a heat pump, getting energy from the outside air and heating the (return-) water going into the conventional heater via plate heat exchangers. I will be moving house twice (temporary home in between) and renovating the new house in the coming months so I will have little time for this project, but I will continue to plan and maybe purchase. The idea in a simple sketch:



(I see I cannot post pics, yet, please copy/paste and add 3 W's and a dot)

The heater is a conventional gas powered heater for my house which also provides hot water (instantly, no tank). The heater is prepared to accept hot water coming in, for instance from a solar heater of heat pump. It cannot run tap water and heating water at the same time, so I can switch the heat pump from one exchanger to the other if I can find the correct valve.

For controls I have a simple plan which will get more elaborate soon, I fear.
- If flow is detected in one of the two pipes going to the heater (F1 or F2), the switching valve is positioned accordingly and the pump is activated. I think I need to program in a preference for one of the two, probably the tap water, because the pump in the heater can run a few minutes after active heating has stopped. Or maybe I can extract a heating signal from the heater to run the pump, that would be easiest.
- If the delta-T over T1 and T2 is too small while the pump is running, the condenser is probably frozen. Stop working and try again in half an hour or so. If it continues to fail like 3 or 4 times, something else is wrong so stop working and switch on a red LED warning light until I can manually reset it after I fixed the cause.

I need to learn how to calculate flows, pressures, dimensions, etc, what I need for this. But here’s where I need help now; I am being offered a big pump for a few bucks. It comes out of a freezer that was in a food store. Should I buy it? This is the plate on the pump:


(I see I cannot post pics, yet, please copy/paste and add 3 W's and a dot)

It is a pretty big pump, I always think bigger is better but in this case I just don’t know. Please advise!

Cheers,

Hugo

P.S. If a longer-time member would be so kind as to post the pics, I'd be forever grateful. Which doesn't exactly buy you anything, but anyway, it would be nice.

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Old 03-01-18, 09:15 AM   #2
HugoW
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I've been trying to read the type plate:
- DWM Copeland
- Max allowed pressure in use; HD/ND 25/20.5 Bar
- Block. Rotorstr. 31-6-34,4 (no clue as to what this means)
- Max 5.8A at 3x 240V in delta configuration, 50Hz.
- 1450 rpm
- Volume 5,14 m3/hr.

Would this pump be useful for my plans?

Cheers,

Hugo
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Old 03-04-18, 07:51 AM   #3
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Here's your pic. Looks to be a good compressor to stick on a 3 phase inverter drive.

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Last edited by Daox; 04-12-18 at 11:34 AM..
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Old 03-04-18, 08:13 AM   #4
HugoW
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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
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Old 03-04-18, 11:25 AM   #5
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Quote:
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.

-AC_Hacker
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I'm not an HVAC technician. In fact, I'm barely even a hacker...
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Old 03-04-18, 02:29 PM   #6
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Input from the AC-Hacker himself, I feel honoured. Thanks! Propane (R290) is second on my list, the fact that can burn makes it sound scary. It probably isn't, the system should have no leaks anyway, but still. It is the refrigerant I find most data about, amongst which the input from German children

Actually, the compressor is a pump, and nothing more. The fact that the expansion valve hinders the flow in the system and the pump has the ability to raise pressure, still makes it a pump. Hence my pump symbol.

The whole idea is still in it's it's infancy. Plans come and go at this point, I appreciate the input. Currently in my head I consider to make the pump for the central heating only. The hot water part of the utility bill (basically, all good ideas aside, that is still the bottom line) is very small compared to the central heating. I might go the solar route for the hot water, or for a second smaller heat pump. This big pump, if all goes to plan, should make a lot of heat. If it indeed has a 400% return, it would make 6kW... It does so in my dreams already, just need to turn it into reality!

Hugo
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Old 01-30-19, 08:03 AM   #7
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Hi, yeah, ah, well… Sometimes life does not go as planned. But things have settled again and this project is close to the drawing board. Not yet on it, as I am planning to make my own Aquion battery system to store my collected solar energy, first. This collected energy could also power the heat pump. The Dutch government is changing the rules on solar energy; next year I’ll be paying about 35 cents per kWh I use and I only get 7 cents for each kWh I give back. So, I need to stop feeding back and just collect it and use it myself.

I’ll be back…

Hugo
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Old 02-28-19, 03:46 AM   #8
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How's it going with the saltwater (ahem, sodium ion) battery storage? Not a bad concept, but those lithium ion setups are so small and less expensive in comparison. If you're trying to use your solar power, just construct an electric heat dump water tank. What works best for you? I can't see it from here.

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