The Homemade Heat Pump Manifesto

[AC_Hacker]

Originally Posted by randen

Just a little side excursion. Have a look at Drakes Landing here in Canada. (www.dlsc.ca)See what they have done with their bore holes. Over 90 % of the heating load comes from the bore holes.

Randen

Wow, now that is something to be proud of.

Looking over the specs for their loop field, I'm surprised that they didn't space the holes further apart.

But interestingly, they did give their recipe for their grout: High solids grout – 9% Blast Furnace Cement, 9% Portland cement, 32% fine silica sand, 50% water.

I'm surprised that they didn't go for radiant floor heating... I've been watching a BBC series called Grand Designs, which follows interesting home builds from concept through completion, and although the series misses the opportunity to focus on energy issues, all of the builds use radiant floors, and every bathroom has a heated towel rack.

But all in all, this is the way of the future.

Maybe someday the US will catch up to Canada.

(BTW, your link needs a bit of a tweak)

Best,

-AC

[cbearden]

Originally Posted by AC_Hacker

I am interested in your Arduino logger setup, too. Be sure to include hardware & sketch info on that part.
Best,

-AC_Hacker

Thanks for all of the suggestions and feedback. Heres a quick pic of the arduino setup. And my sketch that I'm using. It basically has 3 parts to it:
A. setup ethernet connection
B. setup/get temp data from ds18b20 sensor
C. push temp data out to my linux server running emoncms

emoncms is simply a LAMP (Linux, Apache, mysql, php) server setup that stores given data to it, and helps you to easily generate graphs and whatnot from the given data.
I knew I could never put together something like this from scratch, so when I found this open source software I was pretty excited.

The part in my sketch that has the xxxxxxxxxx in it, you'll need to replace with your own apikey that you'll get if you setup your software.
Also, be sure to replace with your own IP address and change the MAC address as you see fit.
I found a typical wiring layout (also attached) for an arduino to a Dallas DS18B20 temp sensor, in case anyone needs more info on hooking this up.

[cbearden]

Here is a screenshot of an example dashboard that you can create with emoncms. At first, I had trouble figuring out how all of this tied together. But once I got the basic ideas down, it's pretty simple to change your graphs up or add on more data feeds from other devices.

[wsexton1]

Hi AC Hacker

I'm very interested in constructing a similar GSHP to what you came up with. I appreciate it was a while ago now. I currently have an 85m closed loop borehole in my property and some underfloor heating circuit laid. I was basically wondering how you went about determining the size of your compressor and other circuit pumps?
Thank you for your post, it was very interesting.

Kind Regards,

William

[AC_Hacker]

wsexton1,

Welcome to the conversation!

A GSHP, consists of three systems:

• a ground-coupled system
• a heat pump system
• a heat exchanger (HX) system

All heat will come from the ground-coupled system.

The heat pump facilitates the extraction of the heat.

The HX system will make the heat available in the house.

The proper way to begin is to assess the maximum heating needs of your house. This need will be expressed in various ways, in the US, it is expressed as BTU/hour. This will usually be on the coldest night of the year. It is actually a bit more complex, but this is a good place to begin.

From that starting place, the next step is to design a ground-coupled system that is capable of supplying heat at that maximum rate. The design will be based on well-understood principles, and will include some testing to assure that the design is actually correct.

The next step is to design (or select) a proper heat pump. The compressors are rated in BTU/hour (in the US), so the compressor is selected based on the maximum heating need of the house. The heat pump will have two HXs in it, so the HXs will be selected to match the compressor's input & output. Again there is a bit more to it, but this is a good starting point.

The last step is to design the system that will bring the heat into the house. In your case, you mentioned that there was some radiant system already installed. The radiant system will be designed to match the output from the heat pump. It is very important to understand that most previously designed radiant underfloor heating systems use fossil fuel, are designed for supply temperatures in the 140F to 160F range. GSHP systems will supply heat in the 100F to 120F range, so a fossil fuel system will not provide the heat rate you seek.

Originally Posted by wsexton1

...I currently have an 85m closed loop borehole in my property...

There are very many factors involved here, that need to be known before an educated guess is possible. But, knowing absolutely nothing about your closed loop bore hole, other than "85m", I will take a guess that has almost no basis in fact, and estimate that it could be capable of around 12,000 BTU/hr, maybe a bit more, possibly less.

Originally Posted by wsexton1

...and some underfloor heating circuit laid.

Again, is the underfloor circuit built for fossil fuel temperatures or for GSHP temperatures? It may or may not be very useful to you.

Originally Posted by wsexton1

I was basically wondering how you went about determining the size of your ... other circuit pumps?

These would be based on the heat needs, which would dictate flow rates, and also pipe length, diameter, etc.

So, these decisions are based on many interdependent considerations, and a proper design would proceed approximately as I indicated, and then final results would be carried back to the beginning, and rechecked for feasibility, and changes made until a final design emerges.

Please understand that my outline is highly simplified to give you the overall idea, and that many other important considerations enter in to a realistic design.

I don't know if you read the entire Homemade Heat Pump Manifesto, but much of the information you seek is there.

Also there are some excellent threads on DIY radiant floors on the EcoRenovator site.

I hope this has been useful to you.

Best,

-AC_Hacker

[wsexton1]

Hi AC hacker,

I have finally managed to read through the wealth of knowledge available on this thread, and I've got to mention how impressed I am.

So to the build...As per your advice I analysed the heating load on the building (new build, 2 years old) and discovered a max heating load of 5kW for the room to be heated. Luckily the underfloor heating circuit was installed recently in a 75mm thick insulated screed floor with 150mm spacing. Which I believe allows for a relatively low flow temp (40-50C).

Onto the borehole (actually 80m deep), which after speaking to a local expert informed me of an extractable heat of around 59W per m giving around 16000 Btu/hr.

Progressing to the heat pump. I have decided to start off on a smaller scale to get some practise and teething errors out the way first time around and see what sort of COP is possible before purchasing a bigger compressor. Potentially putting the second heat pump in series with the first to have the capability of having the system on 'half power' (which I hear may be more efficient anyway). Having purchased an old 14000 Btu/hr mini split unit and having discharged it, I'm now in the process of getting hold of some heat exchangers. This is my question for you at current. Why is it essential for the heat exchangers to be sweat fittings? Only because there are much cheaper threaded versions available here in England.

Additionally, I've estimated the water flow through the ground loop to need to be around 1.8m3/hr (7.9Gpm), for turbulent flow. Requiring around a 160W circulating pump. Is this similar to your loops pumps? Only I happen to have a central heating circulating pump banging around, and I'm more tempted to reuse that than go ahead and buy a great new pump!

Thanks again as always.

William

[AC_Hacker]

Originally Posted by wsexton1

I have finally managed to read through the wealth of knowledge available on this thread, and I've got to mention how impressed I am.

William,

Thank you. It was a lot of work, but I did it in the hopes that people just like you could succeed in a project such as you are now undertaking.

Originally Posted by wsexton1

So to the build...As per your advice I analysed the heating load on the building (new build, 2 years old) and discovered a max heating load of 5kW for the room to be heated.

OK, so when I translate that into my antiquated US (AKA: British) system, I get 17060 BTU/hr or about a Ton and a half. Sounds reasonable.

Originally Posted by wsexton1

Luckily the underfloor heating circuit was installed recently in a 75mm thick insulated screed floor with 150mm spacing. Which I believe allows for a relatively low flow temp (40-50C).

Floor = 3" thick concrete, insulated below, with 6" PEX spacing. (perfect)

Input water temp = 104F to 122F (just the right range for GSHP)

Originally Posted by wsexton1

Onto the borehole (actually 80m deep), which after speaking to a local expert informed me of an extractable heat of around 59W per m giving around 16000 Btu/hr.

Bore hole = 80m = 262.5 feet deep

Local estimate = 59 watts per meter = 4720 watts = 16105 BTU/hr

So far, it seems right on target!

More bore hole is always better, but this sounds just about right.

Originally Posted by wsexton1

Progressing to the heat pump. I have decided to start off on a smaller scale to get some practise and teething errors out the way first time around and see what sort of COP is possible before purchasing a bigger compressor.

Great, just great!

Originally Posted by wsexton1

Potentially putting the second heat pump in series with the first to have the capability of having the system on 'half power' (which I hear may be more efficient anyway). Having purchased an old 14000 Btu/hr mini split unit and having discharged it, I'm now in the process of getting hold of some heat exchangers.

Your idea of multiple compressors is a good one, and your decision to build a smaller test unit for 'proof of concept' is really the only sane way to proceed.

With all that said, I would say that the 14000 BTU unit you now have is a perfect match to your heat load, floor, and bore hole. It will not provide 100% of the heat required for the worst case condition, but the remainder can be supplied by other means.

So, this first build may well be the only build you may need to do, and if you proceed carefully, you may be able to get it right on the first try.

Originally Posted by wsexton1

This is my question for you at current. Why is it essential for the heat exchangers to be sweat fittings? Only because there are much cheaper threaded versions available here in England.

What ever kind of junction you choose to go between your copper refrigerant tubing and your HX will be subjected to two different kinds of stress, mechanical stress from vibration and also thermal stress due to the large temperature excursion which is a result of off-on cycling. Sweat fittings (that I continue to insist should be called 'brazed fittings'), when properly done, will provide a junction that can easily survive both kinds of stress, because a brazed connection makes the HX and the copper refrigerant line become one continuous structure, so in effect you have eliminated the junction entirely.

As a lucky coincidence, you happen to have a fellow heat pump hacker in The Neatherlands who is also at this time, building a heat pump RIGHT HERE.

He is using a Brazed Plate HX which has compression fittings, and he is not going to use a sweat fitting.

It may be that the problem of stresses that a HX is subjected to have been solved through properly-engineered compression fittings. If that is the case, it makes life easier and less expensive.

If you are going to use compression fittings, be sure that you fully understand all of the details of implementing the compression fitting before you proceed. I am thinking of details like assuring that you have made a good flare that is clean and perfectly smooth. Also, does the compression fitting procedure call for using some kind of assembly lubricant on the threads and perhaps face of the metals in the compression area? Lastly, exactly what is the specified torque that is called out for your exact fitting? Too much torque can weaken the union or even ruptured the copper... too little torque can come loose. A properly executed compression fitting, due to the forces, can actually 'weld' the mating metal faces, when analyzed on a microscopic level.

Originally Posted by wsexton1

Additionally, I've estimated the water flow through the ground loop to need to be around 1.8m3/hr (7.9Gpm), for turbulent flow. Requiring around a 160W circulating pump. Is this similar to your loops pumps?

This sound about right. As you probably know there are some very sophisticated pumps available now that can sense and self-adjust to changing requirements.

Originally Posted by wsexton1

Only I happen to have a central heating circulating pump banging around, and I'm more tempted to reuse that than go ahead and buy a great new pump!

Use what you have! Pumps are easy to change out.

As a request from me to you, it would be very useful to me and all the other readers, if we had a better understanding of the local temperature characteristics you are subject to, so if you could go to Degree Days dot Net and calculate your degree Days in both Fahrenheit and Celsius it would be very useful. In fact, if you could tell us what your local temperature monitoring station location is it would be interesting to see what the recorded historical temperature patterns actually are.

Good luck with your project, William (also my son's name)...

Best,

-AC_Hacker

[Fordguy64]

Ran across this while researching my ac conversion to heat pump. Pretty good info on txvs

http://www.emersonclimate.com/Docume...re-article.pdf

[phreich]

Hi AC Hacker,

I have been lurking in this forum and reading your thread on doing a DIY cheap GSHP installation on Portland over the last year or so. I am interested in doing this myself as well. I live in the Portland metro area too. I guess it's about time I made a post.

I am a handyman by trade, and a jack-of-all-trades by predilection. I have been noodling with the idea of a GSHP since I discovered that People's Food Coop in Portland put one in I recall about 10 years ago.

The thing that's been most daunting to me is the trench or bore-hole requirement. I need to put in somewhere between 2 ton and 2.5 ton unit. That means 400-500 combined feet of bore holes (I live on an acre, but am unwilling to deal with that much yard excavation to put in a slinky system). I also don't think that the slinky system really is all that great since it is only 4 feet underground and so is effected by temperature changes in a negative way (when you need heat the ground at 4 feet is colder, and when you want cooling the ground at 4 feet is warmer).

Soooo, I have been trying to figure out a way to drill my own 50 foot bore holes. This would put me above the water table (about 67 feet at my location). I have been looking at some web-sites on drilling your own wells -- mostly by folks in the southern US states -- and they seem to think that 30 feet is about the limit to using a water-cutting method. However, there are folks using a recirculating mud method that go deeper, and one guy in Oregon that uses a combination of compressed air and water to go deeper.
Here are some links on the well drilling:
How to Drill Your Own Water Well
(this guy has been doing this in the deep south for years now. Although it's a .com domain, he's not trying to make money selling stuff -- it's really kind of a forum for DIY wells.
On this site, he discusses various methods, and this is where I found out about the recirculating mud method, and about the guy in Oregon using the compressed air and water method. I'm a bit confused about who this is -- the video is by a fellow named Paul Smith, but the kit is ordered from a guy named Lee on the Oregon Coast.
Here's a link to the video of the Oregon guy's stuff:
https://www.youtube.com/watch?featur...NS4awOxrI#t=37
Here's a page on the first guy's website that discusses this air/water method:
How to Drill Your Own Water Well
Their address to order the air/water kit is:
bluewaterenterprises@Safe-mail.net

No offense, but I think the augur method won't work very well for the depth that is needed at my site.

Soooo, I am looking to self-drill 8-10 50 foot drywells and use a recirculating closed-loop system like you are doing. I see that some folks in the south are using extraction wells and pumping ground water and then disposing of it in drywells. Maybe I am missing something, but it would seem the energy needed to move the water up out of the ground would cost more than the better temperature differential the cooler ground water would have over the recirculated water. I also wonder about the long-term effect of percolating that much water in the summer months into the ground. On the other hand, I could keep my lawn, flower beds, and garden VERY happy in the summer with all that water.

Actually, after writing this last bit about pumping ground water, I am wondering if maybe using ground water might pencil out after-all. Especially if I used it for irrigation purposes, and maybe for a decorative stream and pond. Hmmm, I'll have to think and do some more research on that... I am concerned about what the Oregon DEQ would say about doing this. I think they are scared enough about the possibility of leaking closed loop systems -- what would they think about the possibility of a contamination of an extraction/injection well system?

The major concern, of course would be the heat exchanger process -- if the heat exchanger ruptured, the compressor oils could go into the ground. However, I would think that a safety could easily be set up to shut down the system should the pressure drop due to a coolant leak. How worse or better would the contamination of the compressor oil be compared to the ethylene glycol typically used in close-loop systems leaking into the ground?

Enough of my digression regarding extraction/injection well GSHP....

I also am wondering about using the heat extracted in the summer to produce my hot water, and wonder how much I would save by using the GSHP to heat it from the ground source in the winter (I currently have a natural gas water heater).

[randen]

phreich

I would humbly suggest, if you have the land avalible and soil type for a horizontal ground loop this is the way to go. Drilling bore holes is for smaller land parcels and special applications. There is a lot of work and money involved with building a drilling rig and then drilling the holes after which you still require trenches to couple the tubes then bring it into the house.

We had installed a horizontal ground loop. I had hired a large excavator to move the dirt quickly and the tracks left minimal damage to the lawn. By hiring a large machine the job is accomplished much quicker and actually keeping the costs down. I agree it is a bit of a mess for a season or two. But my lack of an oil bill makes me smile. The money saved after the second season more than paid for the grass seed and a little raking.
The install of the loop took 1 1/2 days. I agree about the slinky system the tubing for part of its coil is redundant. Our install is parallel and no closer than 16" from tube to tube The tube is also placed 6 ft. deep but this can change for different geographic locations (check with local installers). The climate here in Ontario Canada can be quite extreme and I wouldn't want any problems. After all we are looking for greater efficiencies. Overlapping coils and running tubes close together isn't going to gain you anything.

phreich wrote:
(when you need heat the ground at 4 feet is colder, and when you want cooling the ground at 4 feet is warmer). You will need to read-up a little more on the Geo-thermal magic to understand the beauty of these systems. Take a little time reading some of these posts all the information is here.


May I ask, why if you have natural gas do you wish to install Geo-thermal? I would say that the costs of operation are equivalent.

I had our Geo-thermal system for our home install professionally and for my shop I had done myself. Ground loop and the DIY heat-pump. It has been functioning well but it has had some issues. The best part is its saving me a bundle!! Natural gas is not an option here.

I believe possibly the best situation for these heat-pumps is this. YOU CAN MAKE ELECTRICITY!! We are now continplating a solar PV system. If you check the Builditsolar website there is another gentleman there that has done just that. Imaging no heat or electric bill.

Randen