Quote:
Originally Posted by randen
Hello just doing some information gathering for obtaining some brased plate HXs. The GSHP I'm planning is utilizing two compressors rated 2T and 2.5T therefore a HX large enough for 4.5T (54,000) BTU. The two compressors in captivity are split air to air units complete with cap tubes. The 2.5 T has a new compressor the 2T is about 10 yrs with only a few hrs. I have gathered some stainless steel sheet stock (old cabinet doors from a comercial kitchen) for the enclosure. Although stainless can be nasty to work with the benefits no painting and no rust. 20yrs from now it will look the same as the day I had made it. The goal is to heat a 1600 sq ft shop in a Canadian climate with money left for the kids college fund. The shop is well insulated and the office portion has already in floor heating. The plan is to sequence the compressors such that say, after 8 hrs run time the second compressor should start until the thermostat cycles.
Questionable items: TX valves vs capillary tubes.The simplicity of brasing the cap. tubes in and recharging the system would be my personal favourite. Or is there an advantage in COP with the adjustability of the TX valve with the differing temps and associated pressures in GSHP application.?? The other item the reversing valves one for each compressor. The complexity would go up, switching the refrigerant, and switching from floor heating to fan centre (water to air) cooling. The shop always had airconditioning and some days is really needed.
Randen
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This is a pretty advanced project, compared to what I have done.
First, look at the building with a vicious eye to reducing heat loss as much as possible. I posted a link to 'Mooney Wall' construction in the Conservation area, that should give you some ideas. The example they show results in a six or eight inch wall, but it doesn't mean you can't go thicker. And windows are almost always huge heat loosers. Daox had a very interesting post about DIY triple windows.
My inclination is to advise you to consider a separate HX for each compressor, and to run the floor-loop water in series through the two HXs. This wll give you some breathing room as far as HX prices, and also give you a 'soft fail' if one of your refrigeration units has problems.
As far as cap tube vs TXV, the recommendation seems to go with TXV over a Ton and cap tubes under a ton. There are cheap TXVs available on ebay. Make sure you get ones that are compatible with your refrigerant.
I just watched a 20 year old 3 Ton whole-house AC get uninstalled, and it used 4 cap tubes in parallel to share the duty.
...but if you already have the cap tube, use them.
If you are building your first heat pump from scratch, you are flinging yourself into the deep end of the lake.
Maybe go to
HVAC Talk and solicit some seasoned advice, they have some experienced people there, if they will talk to you... well that depends upon the stars.
I'm happy to help you all I can, but this is pretty big and complex. What I have worked with is small and simple.
At any rate, stay in touch, this is just too interesting to miss...
-AC_Hacker