Hi All,
first off, thanks for sharing your knowledge in here, had a long read but the info is very valuable. I might need a bit of help or opinions needed for my project, just in case I am missing some obvious things. What is going on:
I live on a small boat, 27ft sailboat, it's getting freaking cold out here on the Danube, I'm not paying for electricity but I am environmentally conscious and want to be self sufficient if possible, resistive heating is just ridiculous. I have been looking at various ways to heat a small boat and I dislike the majority of them, so I ended up with a plan:
-buy one of the highest efficiency ASHP and convert it to WSHP. I bought a Midea MSX07HRNF1QE4 heatpump (8000btu on heating) with a COP of 5.56 or something like that.
-I figured I will install it myself this winter and run it as ASHP simply because it is getting too cold to diy now and I don't have all the tools required to deal with refrigerant lines.
-when spring comes I plan to swap the outside air coil with a water to refrigerant HX, open loop, add an efficient pump for the loop.
-keep all electronics and everything else intact, hopefully everything just works with the coil swap. And voila, happiness...
Well, what I have to figure out is - what HX to get, capacity of HX, what pumping volume and how to fill in refrigerant after the swap (quantity). The Danube gets close to 0 degrees in winter (mostly around 4degC), but outside air can get to -15 -20, I understand that occasionally this harbour can freeze sometimes (once a couple years).
I looked at my heatpump and made a few observations: it seems everything is as big as the 1 ton units in the same series of the product, the higher btu series seem to have identical hardware but their COPs go from 5.56(8000btu) to about 4.2 (12000btu). I believe but not yet confirmed even the dc compressor is the same in all units from 8000 to 12000btu. The compressor I have is DA110S1C-30FZ, the unit has a cap tube setup, no txv, not sure if I should be sad about it, as I read the TXV's are better as they offer adjustments.
I would be curious on your opinions on the HX and if in general my idea is not completely bonkers. It seems like the unit is pretty much the 1 ton unit, but "underclocked" for a higher COP, the label even says it goes from 2600-12500BTU in heating. So should I get a 1 ton HX or lower ? Also it is a R410A unit, not planning in changing refrg. type.
Before spring comes I assume I will have time to collect some tools to do the hacking, and more knowledge hopefully. I'm thinking of going with BPHE just because they are getting so cheap, and flush out the foulants every once in a while, and provide a decent filter on the river water inlet. Have no idea though what pumping capacity should I push through the loop. Ideally I will be running it on solar power once I finish making my panels, the dc compressor looks to draw very little after start. The interior volume is also very low, but the boat is old and there's not much hope to add more insulation now. I have added mineral wool blankets on the deck and some polysterene boards where possible. Also - an important factor is humidity, gets pretty humid inside, hope the interior unit can get rid of the humidity, it seems to have a separate dehumidification program.
It looks to be hard to get a coax HX around here, but BPHX pretty easy, I know they can foul quicker, but also read cleaning instructions from some manufacturers and they don't seem to really turn into hopeless junk that you can't do anything with if your water source is not clean enough, they can be flushed with some cleaning agents etc. Do you think I should avoid BPHX at all costs ? Also - now I'm on the Danube, but I might get into salt water at some point.
Look forward to hear some feedback on my hacking intentions.
Cheers from the cold-ish boat !
Florin
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