The Homemade Heat Pump Manifesto

[rhino 660]

Originally Posted by go4haudio

The method of sealing was in response to the leaking heat exchanger you had some time ago. But it seems you have mastered the art of brazing a plate HX. I have learned a great deal from your manifesto. I live in Florida where the ground temp at 30 feet is 74 degrees. I did some crude measuring. The soil at the surface ranged from 98 to 105 degrees. 4 1/2 feet below surface the temp was 83 degrees. Since my heat pump will be rejecting heat I think I may device some sort of cooling tower, a column of water that perhaps can evaporate? Of course i would use a closed loop hydronic system. My main concern is that 83 degrees a little on the warm side, especially at night when the ambient air may be cooler. I guess I need to read some temp charts. But it worries me because the temp is bound to go up naturally let alone rejecting heat into it. And it worries me. But how much more efficient would a heat pump be using a water HX vs Air Hx , if any when you compare the same temp for water and air. It seems like a water pump is more effective than a big fan. Any thoughts? Plus I hope your arm is healing well.

you must live in south fl im in sebring and my ground temp from 2' to 6' was 70*f i know in the 50's they used pump and dump hx's on ac units because the aquifer was so close it would drain into the canals in south fl

[AC_Hacker]

Originally Posted by go4haudio

The method of sealing was in response to the leaking heat exchanger you had some time ago. But it seems you have mastered the art of brazing a plate HX. I have learned a great deal from your manifesto. I live in Florida where the ground temp at 30 feet is 74 degrees. I did some crude measuring. The soil at the surface ranged from 98 to 105 degrees. 4 1/2 feet below surface the temp was 83 degrees. Since my heat pump will be rejecting heat I think I may device some sort of cooling tower, a column of water that perhaps can evaporate? Of course i would use a closed loop hydronic system. My main concern is that 83 degrees a little on the warm side, especially at night when the ambient air may be cooler. I guess I need to read some temp charts. But it worries me because the temp is bound to go up naturally let alone rejecting heat into it. And it worries me.

The deeper you can go, the more efficient your GSHP will be.

How much do you know about the soil formations where you live? That could be a big decider as to the best way to proceed.

For instance, here where I live, the soil formations are defined by the ice age and the advancement and retreat of gigantic glaciers 15 to 25 thousand years ago, which left an array of pebbles, cobbles, large rocks and boulders, all of which which are pretty awful to drill through. I felt pretty fortunate to be able to go 17 feet with a small auger and then a shop vac.

If I lived just 30 miles away, there are areas where the soil is often topsoil and sand down to 70 feet. Whole different drilling situation. I could use a rotary drill and drilling mud, and make progress real fast.

There in Florida, I would expect things to be very different than they are here. You just might be in an area that would favor a rotary mud drill. You just might be able to drill down 50 to 100 feet really easy.

I'd advise you to start asking around... talk to water well drillers, talk to GSHP drillers, see if you can find some amateur well-drilling blogs(here's one), search YOUTUBE, pick their brains. If all else fails, contact your local geologist (every state & sometimes every city has one). Find out everything you can about the conditions of the earth that is underneath you. Report back what you find, because there might be other Florida folks that are thinking the same thing as you... That information would be useful to them.

Originally Posted by go4haudio

But how much more efficient would a heat pump be using a water HX vs Air Hx , if any when you compare the same temp for water and air. It seems like a water pump is more effective than a big fan. Any thoughts?

There are too many variables to be really exact, but GSHPs typically have COP of around 3 to 5+, and ASHPs have COPS of 2.0 to 3.5. GSHPs are more efficient for the reasons you identified.

If you can get your ground loops down into the cooler ground you should expect to enjoy the higher COPs... If you are putting in shallower loops, you'll have lower COPs.

If you dug only into the 84F layer, you might not even get performance as good as a mini-split. But if you did the work yourself, you might be able to do the deed for just a few hundred bucks, instead of a few thousand.

So at this stage, I'd say focus on the soil under you. That's going to be a big decider.

And you have a fellow Florida guy right here on this thread. I bet you two could share ideas, and techniques... maybe even tools and do a bang-up job for both of you.

But don't forget to share your progress with us here. I just bet that there are scores of people reading this blog right now, who live in similar climate conditions who are itching to get their hands dirty.

Originally Posted by go4haudio

Plus I hope your arm is healing well.

Thanks for your good words, it is getting better, but slowly... And I really want to get back to my projects.

Regards,

-AC_Hacker

[smith]

Hi took me 3 days but i finally managed to read everything, a lot to take in. I have a smaller area to heat as you did, about 800sqft. I live in Maine, brr cold, ya i know Anyway I'm going to be doing a few of these projects hopefully on the scale that you yourself are doing. the timing is not in the short term though so i should be able to learn the required skills and test(destroy) a couple of AC's before I'm ready to proceed to the building faze. I have a unique area that I feel would work well with boreholes, About 35ft away i have a steep bank about 15 feet that goes into a damp area with a runoff in the middle I'm pretty sure shale or slate is only 10-15' down under that, i have not done a test hole yet. Conditions might be tricky or impossible to drill. I have the space to do horizontal or even set the holes up on top of the bank.

The entire place has been gutted and re insulated and will have new plumbing and wiring, In the short term I'm leaning towards propane for water heating and possible a radiant setup of some sorts(under floor due to a few issues with doing it above).

thanks again for the great information and when i do start doing anything I'll be sure to include photos, I'm sure I'll have a few more questions before that time Hope your recovery is going well.

P.S. I have a web hosting reseller account that pretty much does nothing but cost me money, It would be trivial to setup and account for you on that for you to put together some type of website that has all of this compiled together for easier reading.

[AC_Hacker]

smith, welcome aboard!

Originally Posted by smith

I have a unique area that I feel would work well with boreholes, About 35ft away i have a steep bank about 15 feet that goes into a damp area with a runoff in the middle I'm pretty sure shale or slate is only 10-15' down under that, i have not done a test hole yet. Conditions might be tricky or impossible to drill. I have the space to do horizontal or even set the holes up on top of the bank.

I used to live in New England, and the glacial distribution of hard rocks is pretty much a fact of life, unless you are in an anomalous part of Maine. If you're going to do boreholes, you need to realize that you'll need POWER to get the job done. There was a guy named Vlad further back on this thread that built a really robust hydraulic rig with big water pipe for drill rod. You're going to need something really big like that. Unfortunately, Vlad didn't leave us too much in the way of details of his drill.

As example, a light weight rig wouldn't cut the mustard.

You're gonna need something with some real power more like this.

I'm not trying to be discouraging, I'm actually trying to make sure you succeed.

I have no interest in the above products, and I don't know anyone who has used them. I do know that there are similar rigs built by various companies that you can buy new, sometimes used, and with gumption and persistence you could build your self.

[QUOTE=smith;13037]The entire place has been gutted and re insulated and will have new plumbing and wiring,

I sure hope you got really serious about your insulation. If you read through the blog, you know what an insulation nut I have become... and the more you spend on insulation, the less you will spend heating. 10" walls and triple pane windows would not be excessive for Maine... it my not be normal, but it's not excessive.

Originally Posted by smith

In the short term I'm leaning towards propane for water heating and possible a radiant setup of some sorts(under floor due to a few issues with doing it above).

Are you talking about a propane fired hydronic boiler, or are you talking about a propane fired domestic hot water system?

You could make a propane fired DHW heater be available for backup should your heat pump system fail.

For Maine, I would imaging that standard practice is to use antifreeze of some kind in your loops should your system go down and you not be able to get back to prevent problems.

Also, the advantages of having your hydronic loop on top of the floor is big enough that I would say to do everything you can to avoid underfloor construction. The difference in feed water temp between staple up and some top of floor system can be 30 degrees, and you will pay the difference every hour your heat is on.

I have looked thoroughly at a top of floor system called Warm Board, and it looks to be really good. I have no personal interest in warm board, except that it has really good specs.

-AC_Hacker

[smith]

I need to do a couple test holes when i get ready and figure out what i need, I might luck out i was looking at the usgs soil maps for my area and i'm right on top of a dz(dune zone) with loam around it. Since the ground is consistently wet and somewhat boggy i also though about doing a driven point well, their are some issues involved with this i know but it's a fairly quick setup.

As for insulation I put R19 fiberglass(i know not the best) in the walls and i'm going to overlay that with the double foil bubble wrap reflextic from home depot. maybe even putting 1/2 or 1" foam on the exterior and redoing that. I would like to get the walls up to R25-30 or close to that and the ceiling R40-50 ish.

I already redid the subfloor in the entire place a year ago so the though of putting that much more money into it really discourages me even if the payback is good. I may do some type of mega insulation under the floor, I have space enough to put 10" of fiberglass if i really wanted too. I was also thinking about doing some baseboard hydronic in to the loops, they are fairly cheap.

As for the primary gas heater i am not exactly sure on this yet, i like the instant hot water systems. not sure of what's best at this time. I also can incorporate wood heating into the mix as I'm basically in the woods.

Is it time for me to start cutting narrow channels in my floor to run the tubing in... the sub-floor i installed is the 3/4" home advantage brand osb from home depot. has an older floor under it so i wouldn't think channels would affect it much, now not really sure of the best way to go about something like that would be.

[AC_Hacker]

Originally Posted by smith

Is it time for me to start cutting narrow channels in my floor to run the tubing in... the sub-floor i installed is the 3/4" home advantage brand osb from home depot. has an older floor under it so i wouldn't think channels would affect it much, now not really sure of the best way to go about something like that would be.

Gary, over at build it solar did a built up floor and made his own spreader plates, too.

You should be able to do something like that after you've routed your OSB.

What you put over your PEX & spreader plates is important too. The higher the R-value of your covering, the more heat you will drive away from your living space.

Personally, I'm considering a similar floor, covering the PEX (on 8" centers) & plates with 1/4 hardibacker, then linoleum (both low R-value materials). I have seen some really nicw linoleums from Europe with the awkward name Marmoleum, but they have some great colors and are 100% organic, so you won't be trapped in a tight house during the winter, breathing poison gasses.

Also, regarding the use of radiators, the principles are this: Lowest feed water temperature favors highest efficiency. Largest radiating area favors lower feed water temperatures.

Most radiators offered in the US assume a fossil fueled boiler, high feed water temps. So smaller radiators are appropriate... but they aren't an efficient match for a low feed water systems like heat pumps, or solar.

There are large-area radiators being used in Europe and you can order them special here, but it would be cheaper and 'cleaner' to put in a high-efficiency floor.

Even most radiant floors done in the US assume fossil fuel boilers, so the PEX spacings, etc assume higher feed temps.

What you are trying to do goes against the grain of common building practices. People will tell you that you are going too far, that it's not needed, that you are wasting your money. If oil was $18/barrel, and would stay that way, this would be true... but oil is currently (as I write) above $100/barrel and the long term prognosis is that it will trend up...

There was a nice hydronic 'tip sheet' posted by a UK reader. It assumes a concrete floor, but the same principles apply to a built floor.

Insist on efficiency.

We have a DIY radiant floor thread... keep us posted on your progress.

Best Regards,

-AC_Hacker

[randen]

The methods we utilize for the space heating is extremly important. In our home in Canada burrr I had attempted to heat a room over a garage. The garage has in-floor concrete heating but being its not a living area we don't heat it very much (60-65deg.Slab temp75 deg.)The bedroom I had installed loops between the floor joists. Even for just a few more BTUs it was completly ineffective. The room is dam cool with a northern winter wind on the outside wall. Even though at the time we had an water temp of 180 deg.F there was no heating for that room. Now with the Geothermal the water temp is only 105deg.F that underfloor system has no hope. However the main floor concrete slab is the holy grail of low temp heating. There is nothing like a cup of coffee on a sunday morning with bear feet on a warm tile floor (88 degF) looking out the patio door at a -10deg F.wind wipping up the snow.
I don't want to discourage anyone but the benifits to the system are huge. The comfort, uniform steady warmth and the cost to operate. Oil fired heating was costing us more than $5000.00/yr. now with geo thermal $1100.00/yr

The method of tubing routed into a OSB strand board may be effective expecially with some aluminum sheet stock formed into the void and around the tube to dissipate the heat. Keeping the tubes closer helps 8" centres.

My project this summer is now the shop. We removed all the conventional oil fired forced air equipment, maybe a little too soon its still cold here. The real down side is we will have to remove 1200sqft of good concrete floor to install ridgid foam insulation and a new floor with a loop. We have been contacting excavators to dig in our loop 4 ton. For our area thats about 2400 lin ft. We have a very heavy clay soil here and we will be placing the 3/4" dia tube down 6ft. I've obtained 2 compressors 2 tons each. I'm thinking of a double compresor system like that was posted earlier.

Randen

[AC_Hacker]

Originally Posted by randen

... bedroom I had installed loops between the floor joists. Even for just a few more BTUs it was completly ineffective. The room is dam cool with a northern winter wind on the outside wall. Even though at the time we had an water temp of 180 deg.F there was no heating for that room...

I had my doubts all along about the wisdom of using heat pumps with under-floor heating... now my doubts are removed and I am certain it will not work. However this situation makes me need to ask about the insulation in the area above the garage. It would be very useful for me to know what kind of insulation you had there... in the ceiling, the walls, the floor (especially under your PEX piping).

In the days of cheap fossil fuel, slap-dash insulation would do good enough. With the practice of low-temperature heating, you really need to hold onto every BTU ‘til it screams.

Originally Posted by randen

There is nothing like a cup of coffee on a sunday morning with bare feet on a warm tile floor (88 degF) looking out the patio door at a -10deg F.wind wipping up the snow... Oil fired heating was costing us more than $5000.00/yr. now with geo thermal $1100.00/yr

You do paint a good picture.

Originally Posted by randen

The method of tubing routed into a OSB strand board may be effective expecially with some aluminum sheet stock formed into the void and around the tube to dissipate the heat. Keeping the tubes closer helps 8" centres.

Yes. Closer spacing would be even better, but there is the matter of bending diameter. I believe that the bending diameter of 1/2“ pex is 8“. But 6“ (or even closer) would be great if the PEX wouldn't collapse.

Originally Posted by randen

...we will have to remove 1200sqft of good concrete floor to install ridgid foam insulation and a new floor with a loop.

Don’t forget the slab edge insulation, very important.

Thanks for the report, best of luck with the on-going project.

Regards,

-AC_Hacker

[randen]

Originally Posted by AC Hacker
It would be very useful for me to know what kind of insulation you had there... in the ceiling, the walls, the floor (especially under your PEX piping).

We had used R20 fiberglass bats The exterior walls are 2x6 and the finish is 2" Drivit stucco which is expanded foam. Very nice finish & seals the house nicely. You are very right in the day of cheap dinosaur heating insulation was a question of minimum building code and pay-back period. Now we should invest greatly in insulation it will pay in great dividens as energy rises exponentially.

The heated concrete slab would require a thermal break around as well as under.

Randen

[Vern2]

Back in the day when I was traveling for work, I stayed at a furnished leased condo, in New Mex. That was one on the worst nights I spent out of town. It had heated floors. The noise from the floor heating and cooling all night was an eye opening event. If in floor heating on general does that, NO THANKS. I'll stick with ASHP. Don't know if that's the norm, but how do you stop the creaks, pops. cracks???