The Homemade Heat Pump Manifesto

[pachai]

Randen,
Did "you" dig it up?
or did you have someone do it?
I'm trying to get an idea what a backhoe should cost to dig some ditches...
Thanks
Seth

[AC_Hacker]

Originally Posted by randen

What a mess. We had a nicely turfed lawn and I tore it up. Maybe the memory of this will fade as I'm nice and cozy in the shop this winter.

I am amazed at how quickly the ground can heal itself. I take great pride in taking people to the back yard and describing the work I did and, through my story, helping them to 'see' the network of underground piping that they are standing on.

Originally Posted by randen

The ground loop of 2400' lin. ft. was installed in a trench 6' deep in clay soil. Actually 4 x 600' loops. The 3/4" tubes where welded into a 1 1/4" header. The 1 1/4" tube was insulated and ran into the shop wall to the utility room. The system was pressure tested and the dirt pushed into the hole. The process took two days.

Wow, great progress... heavy equipment rules!

So, do you have any details (and photos?) on how you welded your HDPE manifold? Using my home-built HDPE welder, I was only able to do butt welds... sounds like you probably rented some socket welding gear. If that is the case, I have never done socket welding and I'd really like to know how it went for you.

Originally Posted by randen

For the compressor,it was harvested from a 3.5T air to air unit. The compressor may have 80 hrs use on it "basically new".

Great find. Sounds like you did it right by building your loop field capacity larger than your compressor capacity. To my way of thinking, even going 2X your compressor capacity would not be extravagant.

It may take a year or two for the earth to completely settle into place around your slinky tubing and for you to have the full capacity of your loop field available.

Originally Posted by randen

I will order some plate HX's and have some fun.

It's been an interesting adventure for me to find inexpensive HX's that I can use for a GSHP. I don't know if you are in a position to be able to buy properly-sized new ones from a vendor. That would be the simplest but most expensive way to go. Vendors should have technically trained staff that can match the right hardware to your needs.

If you're gonna go with used or economy HXs, the adventure begins...

Previously in the thread, I tried to clarify for myself, and for the 'manifesto' readers how this might be done.

But briefly:

• It is a good idea to over-size your HXs by 15% to 50%...
  
• The physical size and configuration of the evaporating HX and the condensing HX will be (about) the same.
  
• HX's that state their capacity for water-to-water will not be correctly sized for refrigerant-to-water because of the very high heat transfer capacity of water as compared to refrigerant... you'll have to locate data for the nearest sized R-to-W HX, and go with that.
  
• If you can't locate the right sized or right priced HX's, it is possible to use more than one for the condenser and evaporator. if you combine them in series, you will be combining their resistance to fluid flow. Not an issue if they already have a fairly large cross-sectional area (width x height). If you combine them in parallel, you will not be adding resistance to fluid flow, but you'll need to provide each evaporator with it's own cap tube. If you're going with a TXV you can bring your cap tubes together in a brazed up header, shortly after the TXV.
  
• If you carefully saved your cap tube(s) from your donor AC, and do your best to resurrect your new heat pump in a similar fashion to it's old configuration, your work will be simplified.

Originally Posted by randen

The stainless item in-front of the compressor is going to be a double 4way valve. I plan to switch the flow of glycol-water mix from one HX to the other for heat/cool in stead of the refrigerant reverse valve. This 4 way double valve always will cause a counter-current flow of refrigerant/glycol mix through the HX's. The valve maybe motorized but for now just a winter/summer switch. We have some scraped stainless sheet stock that used to be in a commercial kitchen that will make a nice box for the unit. The electrical control will be simple a 24V relay with a timer and high/low pressure switch for protection.

Sounds well thought out, and sounds like it will be a nice looking job.

Originally Posted by randen

The circulation pumps are here and before the hack I'm going to try circulating just water through the ground loop and air handler to see if it will cool the shop. The ground loop water temp. is about 58 deg F.

I guess you already know about the proper purging procedures... I initially tried to flush my loop field with a regular circulation pump (which was too small for the task). I ended up using a pump that was considerably larger than what would be required for adequate circulation, for purging, and even that took a while. There is a linear feet per minute rate (google) that is used for purging, and my experience is that the rate is not exagerated at all. I ended up using a biggish sump pump for the job that delivered less than the specified rate, and I had to purge for a day or two to get all the bubbles out.

I also noticed that in spite of all my efforts to keep all the HDPE clean inside, that some debris was flushed out, along with the trapped air. Since the galley ways in the brazed plate HX's are pretty small, you want to get ALL the debris and crud out of the lines.

And as a final consideration, if you can get or make distilled water for your loop field final fill, your brazed plate HX's will have virtually no fouling.

And don't worry about burdening us with too many photos... there's no such thing.

Best Regards,

-AC_Hacker

[randen]

Pachai

Did "you" dig it up?
or did you have someone do it?
I'm trying to get an idea what a backhoe should cost to dig some ditches...

No can't take the credit for the digging. Hired a contractor I haven't received a bill yet but I did ask them to bring their largest machine even then it took 8 hrs to dig and about 6 hrs to back-fill @$160.00/hr $2200.00 Plus a contractor to weld the tubing 6 hrs (he also helped rolling out the tube)Plus the cost of the tubing and fittings maybe about $3500.00 all together or the cost of propane for one seasons heating. I may add that the loop we had installed for the house was $8000.00 OUCH. But after the 2nd heating season it's half paid for itself. You may just call some of your local contractors and have them over to look at your project and provide you with a quote.

Randen

[randen]

AC Hacker wrote:
So, do you have any details (and photos?) on how you welded your HDPE manifold? Using my home-built HDPE welder, I was only able to do butt welds...

I'm sorry I didn't get any photos for the tube welding. You are right the pin and socket welding is very cool, heat both the internal/external of the fittings to becoming very soft and slide together. With the right tools, easy. It did require two persons. I'm totaly amazed with anyone that can turn a George Forman grill into a tube welder. I'm in the tool & die business and after 10 hrs a day in-front of a machine I don't like making something I can borrow or rent after all who needs the practice. Now converting the a/c unit into a GSHP that looks like fun. "One mans junk is our treasure." Machining a valve that dosen't already exsist. Brazing some tubes and a little wiring to save about $5000.00 I'm in. I will post more on the valve as its perfected. The heat exchangers will be a little oversized, better that, then lose some efficiency. The cap tubes I have, but would the DXV valve be a good investment??

We are currently plumbing the loop into the air-handler to see if cooling the shop can occure without the heat-pump. I will post the results soon. Temps now about 34 deg.C or 95 deg. F out-side here. I was going to try the circ. pump for purging. Thanks for the heads up we'll employ a larger pump. Thanks

Randen

[AC_Hacker]

Originally Posted by randen

...Now converting the a/c unit into a GSHP that looks like fun. "One mans junk is our treasure." Machining a valve that dosen't already exsist. Brazing some tubes and a little wiring to save about $5000.00 I'm in. I will post more on the valve as its perfected.

That's the spirit!

Originally Posted by randen

The cap tubes I have, but would the DXV valve be a good investment??

I think so, it make it easier to make a proper adjustment.

...also, if you shop around, you can pick one up pretty cheap.

You will need to know the refrigerant type... (TXVs meant for R-22 will also work for R-R290 (propane)). Otherwise, get a TXV that is specified for your desired refrigerant.

You'll also need to know the capacity of your system... in your case that would be 3.5 Tons.

Also, your cap tube(s) are specific for your refrigerant, again, R-22 cap tubes are very close to those required for R-290. Other refrigerants will need a cap tube length and ID combo, specific for the refrigerant you choose.

And your cap tube(s) I guess there were maybe three (possibly four) of them, will come together in a header... they were probably that way in your AC... if you were careful, you cut the tube a few inches (at least) above where the cap tubes were brazed, an you won't have to re-fabricate that header part.

That tube where the cap tubes connect will attach to the 'out' part of the TVX.

Yeah, making your own heat pump is interesting, for sure...

Have you lined up a vacuum pump?


Regards,

AC_Hacker

[pachai]

Originally Posted by randen

Pachai

No can't take the credit for the digging. Hired a contractor I haven't received a bill yet but I did ask them to bring their largest machine even then it took 8 hrs to dig and about 6 hrs to back-fill @$160.00/hr $2200.00 Plus a contractor to weld the tubing 6 hrs

I may add that the loop we had installed for the house was $8000.00 OUCH. But after the 2nd heating season it's half paid for itself.
Randen

I got the first quote - 150' of trench, 6-8' deep,
3' wide. With shoulders for trench safety.
$7600. Removal of old driveway 100' $1800.

It's a tight lot, so it will actually be 3 digs.
dig, put dirt on side.
Put in pipes.
Backfill with dirt from second trench.
Repeat for 3rd
then backfill last trench with original dirt.

It seems a bit high....but it is a basis for
comparison when I ask the current GC for a
quote. Everything there seems to be $$$$.
(The current GC is bringing in a backhoe to
take out the old driveway, so it might be le$$.)

[AC_Hacker]

randen, pachai & 'The master plan',

This is all so great, Summertime and so much earthwork going on!

randen & pachai, I don't know if you have peeked in on what's happening on another thread by 'The master plan', but he has it going on too, with photos of his slinky coils about to get buried... He's going with a ground temp circulator only... He's a little hesitant to hack an air conditioner, but then the earthwork is the most formidable part of the project.

To my way of thinking, hacking the heat pump is dessert.


Best Regards,

-AC_Hacker

[pachai]

Originally Posted by AC_Hacker

randen, pachai & 'The master plan',

To my way of thinking, hacking the heat pump is dessert.

So, isn't dessert at the end of the meal?
I'm busy moving a laundry sink where a
window became a doorway -
learning to sweat solder, etc.

Giovani laid tile in the kitchen today,
so the cabinets should go in by the weekend....
so I should get my workshop (cabinet
store room) any day now...

Then I can hope to take apart some AC units
in my excessively copious free time.

(Solar guys called today to check the roof :-) :-)

[Vern2]

pachei,

Sorry had a stroke. I'm keeping up with most guys with half a brain. Somethings are still difficult, and comes from left base.Introduction

[pachai]

I had the plumber leave me the option of adding a heated towel bar to compliment my radiant floor.
I was thinking along the lines of what Radiantec
suggests here http://www.radiantec.com/pdf/Install...towel_rack.pdf

But I have a question for those who know about
various plumbing fixtures, etc.
Can I use pipe that is more attractive than
copper? eg, stainless? (expensive)
bronzed brass? (is it available?)
(Chrome 24" is $35 as opposed to $12 for 10' copper)

My thought if I used regular threaded pipe would be to use regular threaded elbows to match, stub it into the wall cavity, and then adapt it to the 1/2" PEX.

Or, I could just use copper and spray paint it to match the Delta Oil Brushed Bronze...

recommendations appreciated
Seth

PS it's Way Off Topic, but....we bought a mirror for the Master Bath and THEN thought about a medicine cabinet. No Worries, the Internet is great. I can build a medicine cabinet for this large mirror....