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AC_Hacker · 05-07-09, 01:24 PM

The following post appeared on Ecomodder at this URL:

The Homemade Heat Pump Manifesto... - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

...I have moved it over here so as to centralize the discussion.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

cptrdbrd wrote:

Hi guys
I have looked over your thread, the threads in twister and some others. I am a commercial industrial HVAC tech for 25 years and tough it for about 10 years in the evenings. I have enjoyed watching what you and others are doing. some times I'm impressed, some times I shake my head and some times I'm just scared. I am looking to build my own Geo heat pump unit by cannibalizing my air to air HP. I have seen some comments elem ware referring to the so called secret info in this info. Please do not believe this is true, I think most techs would love to share there knowledge. the reason it seems they play there cards close to there chest is: it is a very technical field That takes a extensive back round including the laws of thermodynamics, physics, chemistry and electricity theory. this does not mean that the common man cant do what you are doing, but to make it work well and last you Need a few things under your belt. I think you guys can do very well be cos you have desire the #1 thing to synced.
I have held off interjecting be cos there is no short way to learn well the vapor compression cycle and the other things involved. I hope to make a write up that will be usefully some day. for now, till I come up with some thing I will answer your questions if you are willing to share the knowledge you have.
although I have lots of experience with water source heat pumps and water cooled units I am looking for the info for the ground source loops.
Paul

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

AC_Hacker replied:

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=2&Q=268236

Also try using this serch string in Google (remove %):
+"Ground Source" +"minimum standards for construction"

http://www.google.com/search?q=Groun...=Google+Search

Does this help?

>>>>>>>>>>>>>>>>>>>>>>>>>>

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?

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
NOTE: While waiting for a reply, I found what appears to be a pretty good brazed plate selection program. Found here:
GEA PHE Systems North America
...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, and heat is in BTU/hr.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Best Regards,

-AC_Hacker

05-07-09, 01:24 PM	#42
AC_Hacker Supreme EcoRenovator Join Date: Mar 2009 Location: Portland, OR Posts: 4,004 Thanks: 303 Thanked 723 Times in 534 Posts	Post that appeared on Ecomodder... The following post appeared on Ecomodder at this URL: The Homemade Heat Pump Manifesto... - Page 2 - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com ...I have moved it over here so as to centralize the discussion. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% cptrdbrd wrote: Hi guys I have looked over your thread, the threads in twister and some others. I am a commercial industrial HVAC tech for 25 years and tough it for about 10 years in the evenings. I have enjoyed watching what you and others are doing. some times I'm impressed, some times I shake my head and some times I'm just scared. I am looking to build my own Geo heat pump unit by cannibalizing my air to air HP. I have seen some comments elem ware referring to the so called secret info in this info. Please do not believe this is true, I think most techs would love to share there knowledge. the reason it seems they play there cards close to there chest is: it is a very technical field That takes a extensive back round including the laws of thermodynamics, physics, chemistry and electricity theory. this does not mean that the common man cant do what you are doing, but to make it work well and last you Need a few things under your belt. I think you guys can do very well be cos you have desire the #1 thing to synced. I have held off interjecting be cos there is no short way to learn well the vapor compression cycle and the other things involved. I hope to make a write up that will be usefully some day. for now, till I come up with some thing I will answer your questions if you are willing to share the knowledge you have. although I have lots of experience with water source heat pumps and water cooled units I am looking for the info for the ground source loops. Paul %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% AC_Hacker replied: 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=2&Q=268236 Also try using this serch string in Google (remove %): +"Ground Source" +"minimum standards for construction" http://www.google.com/search?q=Groun...=Google+Search Does this help? >>>>>>>>>>>>>>>>>>>>>>>>>> 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? >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> NOTE: While waiting for a reply, I found what appears to be a pretty good brazed plate selection program. Found here: GEA PHE Systems North America ...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, and heat is in BTU/hr. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Best Regards, -AC_Hacker Last edited by AC_Hacker; 12-24-10 at 01:20 PM..