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Originally Posted by Drake
AC, You say your incoming water temp is 40 degrees? Should not water from ground loop be in mid 50's?
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Yes, it started off at 51F, and as I have been extracting heat energy from the loop field, the temperature has been dropping. It dropped fast at first, but has leveled off somewhat to near 40F as time goes on. I can't tell how much farther it will drop. I'm also about to build Heat Pump #2 which will produce (extract) almost twice as much heat as the prototype unit. I will be very interested to see what kind of temperature drop curves that will produce. My plan is to run it intermittantly. I have an Arduino controller that will do the intermittant cycling, the next firmware will incorporate temperature sensing and duty-cycle modulation into the intermittant operation.
Quote:
Originally Posted by Drake
And you has said how cap tube should be right one for compressor, have you saved matching tube with each salvaged comp or can proper one gotten from other source?
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Yes, I have been very careful to save the cap tube with the compressor that it came with. That is really the key to making the homemade heat pump go together easily. There is free software available (DanCap) for sizing cap tube, and charts that do the same thing, but re-using the cap tube saves dollars and hours.
Quote:
Originally Posted by Drake
In your Beta design the ground loop water has a "holding tank"? In theory this tank could get it "heat" from solar source as well potentially?
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Drake, you must be reading my mind (or else my blog... sometimes even I can't tell the difference).
I now see a need for two kinds of heat storage... one kind for smaller amounts of energy, where the energy stored will be of short duration, like an hour or two. In hydronic heating this is usually referred to as a 'buffer tank'. I would guess that the efficiency of energy deposit and energy withdrawal (to use banking terms) should be as high as possible.
The other kind would be more of a mass-energy storage, like grabbing as much solar energy as possible (making hay while the sun shines) and calling upon it later, for future use. Here I dont' think the efficiency would need to play such a crucial role as capacity.
But back to solar gain, I have several flat plate solar collectors in the back yard for that very purpose. I'm thinking now that the mass-energy holding tank should be pretty big to hold a useful amount of heat from the sun... Alternately, I'm considering running solar heated water through the ground loop itself for heat storage.
I'm also very intrigued by Phase Change Materials (AKA:
PCM) like parrafin and eutectic salts. In case you are unfamiliar with the idea, when these materials transition from solid to liquid and back again, a very large amount of heat is transferred into and then out of the material. PCM are not as inexpensive as water or sand or rocks for heat storage, but they have much less volume and mass for the amount of heat stored. Since my house is pretty small, they have an appeal.
But, another appeal of PCM is that when the heat is being stored, unlike water, there's very little temperature rise in the PCM, so the 'delta-T' stays pretty much the same and the heat storage continues at a high rate. This can have an efficiency-increasing effect on heat storage.
PCMs have been widely recognized for quite a while, and have held the promise of being the Holy Grail of heat storage, but for some reason they have not really found their place in the sun (appropriate pun).
So, I have 50 pounds of driveway salt that will either work for me, or will make it clearer why PCMs are not being used.
Quote:
Originally Posted by Drake
I too am most interested in water to water for heating. What I have found from hydro install info is 7/8 pex is recommended for best under joist heating and needs higher temp than "in floor" so if you can do even your durarock install you should be better off. Was also told efficiency of 3/8 and 1/2 pex(just need closer 3/8, maybe more loops) is same if you are really limited on wieght/thickness.
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Yeah, I think I have heard similar regarding the diameters. I wish I could find something that was more specific regarding diameter and spacing and heat output.
If you knew what the heat load was and the square footage, then you could start thinking about the BTU's required per square foot. I have an idea what I want my feed temperature to be (80 to 90 degrees F) and I know I want to do a "sandwich" floor due to weight issues. So now I am at point of determining diameter and spacing, and I don't have a good way to proceed...
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Originally Posted by Drake
And as your mystery puddle shows I have learned hydro cooling is limited by condensation problems(why A/C's have drip pans I am told). On topic of your whole hydronic system if you haven't discovered it already explore "open systems" it is exactly the install for my needs. Even incorporates some cooling possibilities.
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By "open systems", are you referring to mixing heating water with potable water?
If that is what you mean, I'm afraid I don't see the cooling tie-in...please explain.
-AC_Hacker