Paul,
Welcome to the conversation.
When I started this "manifesto" thread, I had in mind that it would be a kind of 'open source project' where people could share their knowledge. So, when folks like you join in, it is very encouraging.
I'm not sure if you know that although this is where I started this project thread, it's moved over to the sister blog:
The Homemade Heat Pump Manifesto - EcoRenovator
...it was driving me crazy trying to double post and remember what was said and where.
Anyway, on the other blog (above URL) there's a ton of additional info.
And I'm figuring this thing out as I go along, so if you see things that need correcting, let's get things cleared up.
> ...I am looking for the info for the ground source loops...
The best source of info I have found is the IGSHPA book, "Closed-Loop Ground-Source Heat Pump Systems: Installation Guide". It's not cheap, and I wasn't able to find a copy that was used that was much more reasonable.
IGSHPA manuals are here:
Publications | Manuals
What I've been able to determine is that there are different ways to get the Ground Source heat. Some are cheaper than others. ranking from cheapest to most expensive goes something like this:
1) Closed Loop Pond
2) 'Open Loop' pump & dump systems where you take water out of an aquifer and dump it back to the aquifer or to a river or use it for irrigation.
3) Trench type systems using a 'slinky' arrangement or a linear pipe arrangement.
4) Closed-Loop boreholes.
Geology or lot size may make one of the choices the only choice that will work.
So, I live on a 50 x 100 city lot and don't have enough room for anything except drilling down. I can't affford to have a professional do it, so I'm trying to do it all myself.
Sizing the loop field is a matter of knowing what your building heat load is and knowing what the thermal transfer characteristic of your particular soil is. On the other blog, I set out how to test your own soil to determine what your heat transfer rate is.
Thermal Test URL:
The Homemade Heat Pump Manifesto - Page 2 - EcoRenovator
...post #18...
So, for me and my small house, I'm figuring my house's heat load to be about 12,000 BTU/hr (a Ton).
In these parts (Portland, OR) the rule of thumb is that a borehole needs to be between 175 and 225 ft deep, per 12,000 BTU/hr. When I tested it, it came out to 214.23 ft. This would mean that I would need at least 214.23 feet of borehole. More borehole is better, and also more expensive.
I have heard that around here, a 5 foot deep by 3 foot wide trench with 300 feet of slinky loops would get you about 12,000 BTU/hr.
I also found out that the material of choice for loop fields is High Density Polyethylene (AKA: HDPE). Many states are insisting that all joints be heat-fused (AKA: welded). Installers guarantee these for 50 years, but the general agreement is that they'll last a couple of hundred years, or more.
Here's product information from a typical HDPE pipe provider:
http://www.superlon.com/supertherm.pdf
There are also considerations of providing flow turbulence, to improve heat transfer. The IGSHPA manual covers this.
Here's a link to a brief blog discussion on the subject of flow rates:
http://www.eng-tips.com/viewthread.c...227114&page=10
PVC pipe is not recommended because it gets brittle with age. I have read, however, that the first GSHP developments did use PVC. I don't know if all of the PVC installations failed, in fact, I don't know if any of them failed.
I have also heard stories about how "a neighbor buried garden hose in the back yard to heat his house". I have no way to verify the information as to whether this will actually work.
I do recommend experimenting.
I also recommend being aware of standard methods, if for no other reason than it can suggest a starting point.
Here's Washington state's standard:
http://apps.leg.wa.gov/wac/default.a...te=173-160-453
Here's from Lancaner county Pennsylvania:
http://www.co.lancaster.pa.us/planni...p?a=3&Q=268236
Does this help?
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And I do have a question for you:
I have this little 400 watt compressor, and I'm trying to size a pair of flat plate heat exchangers for it. By my reckoning, it will move about 1600 watts (about 5500 BTU/hr), steady state. I'll be pumping water in at maybe 47 degrees into it on the Ground Source side, and I'll want in the neighborhood of 5000 BTU/hr out on the hydronic floor side. I figure I'll run R-22 or similar refrigerant. I'm not trying to heat my whole house, just a room that needed about 4000 BTU/hr on the very worst day last winter.
I threw one together last summer and it worked pretty well, but I'd prefer to have a better idea of what I'm doing.
Do you have charts or sizing programs that you like to use?
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NOTE: While waiting for a reply, I found what appears to be a pretty good brazed plate selection program. Found here:
http://www.flatplate.com/resources_SOFT.htm
...choose the "Refrigeration Heat Exchangers" option.
The specifications for ebay-available brazed plates is pretty much non-existent. There is some vague mention of BTU transfer for solar-heating.
Problem is that refrigerants have a very different specific heat, compared to water. So I Thrashed around through several brazed plate selection guides and found that for refrigeration purposes, both evaporation and condensing, heat-transfer seems to work out to about 5000 BTU/square-foot for small exchangers.
So the formula might look something like:
Heat = ((width) x (length) x (# of plates - 2)) x 5000
...where width & length are expressed in feet.
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Best Regards,
-AC_Hacker