Pond Boss Forums INTRO Questions & Observations Geothermal Heat Pump

Heating the slab will warm the whole room. The best part is that the room will be warmer at the floor (where your feet are) than at the ceiling. I would not expect to get enough hot water from the geo system for this, but I could be wrong. The geo only makes hot water when it is heating or cooling air for the ductwork. There are geo systems that only make hot water, but this is a different animal. In the winter, I use all the hot water it can make for showers and domestic use.

I would not recommend installing the pond loop pipes yourself. Not because it is difficult, but because they use a specific type and size of pipe. The installer will probably go ahead and run the pipe all the way to the pond while he is there anyway. Installing the PEX tubing took me the best part of a day to put down 1800 sq ft in my basement floor.

By the way, I know this might be different around the country, but my system has 3000' of 1 1/2" pond loop. The rule of thumb for our climate is 500' per ton.

magic heat Pumps

don't rememeber if this has been posted here

http://www.motherearthnews.com/Renewable-Energy/2005-04-01/Geothermal-Heat-Pumps.aspx

I love this magazine--been reading it for years

We have the same rule in Iowa. Out system has 2500 ft of tubing in the pond and about 800 ft in the ground. We had only puddle of water in the pond our first winter in the house. Top third of the coils was sticking above the ice but the house was still warm. Inlet temperature to the HP was around 26F for about a week during a cold spell. The coils were apparently covered in ice to the bottom.

On a note, here in mid central Indiana our pond did freeze over for about a week--we had some pretty extreme single digit temperatures for awhile. We think we are going to put two aerator stones out this year vs the one off of our windmill--may or may not help. The cost of a service agreement is only a couple hundred a year. Now your loops are usually 10 years (you have all your regular manfacturer warranty on your system etc). On the problem we were having with the heat strips on, sizeable electric bill this past month and probably one more--the geo installer came today and spent a couple of hours doing analysis readings and the like checking everything out. The unit seems to be doing what it should at this time. As Ladia noted there is a lot of adjusting that has to happen based on each persons individual circumstance. One thing he brought up that will be looked at is the 'fluff' of the coils in the pond along with an analysis of all the readings. I have faith it will all come out fine in the end. We are installing a newer Carrier thermostat that will tell us exactly when it is stage 1, stage 2 and stage 3 along with when the Heat Strips kick in - Yippie! One must remember when you live in extreme climates in the north, there will be occasion that the heat strips may engage so you don't want to turn them off (you're just hiding some other unforeseen problem you probably have with your geo). I will let y'all know what the end results are so others who are going geo can be conizant of things that can and do go wrong while tweaking your particular system. Honestly, the price I paid for geo is a bargain compared to what it will give me when it pays for itself in 4 more years. dot

I would still turn the heat strip breaker off but watch when and for how long the thermostat would turn them on and what is the effect on comfort while they are disabled. If they wouldn't come on at all or very seldom only then I would turn the breaker back on. Provided that the heat pump is working properly disabling the heat strips shouldn't have noticeable effect on comfort.

We know the solution coming in from the pond (temperature-wise was too cold) caused the geo to not geo. Hope to get a fix on that. Should have that thermostat in in a week or so and be able to visualize changes.

The moral of the story is that it doesn't matter how much tube you put in the pond if it isn't installed (fluffed and/or purged) properly.
I have never seen aerator stones in a pond in action but, if placed under or in close vicinity to the coils, they might promote water circulation trough the coils. It is just an idea. Maybe somebody can tell us if it is worth considering.

I'm thinking you're on to something, Ladia.

http://www.mercomarine.com/gallery/floating%20house.html
Here is a link to a floating house for inspiration

I've got a guy coming out tomorrow morning to discuss the viability of going geo, using the north pond as the heat sink. I already understand that one of his first steps would be to measure/evaluate my home in order to properly size the system.

What else should I expect on this first meeting? Any suggestions would help, as I've no real idea how this all works...shooting blind here.

On the bright side, I found him on the Iowa IGSHPA (Ia Ground Source Heat Pump Association) database. Hopefully, that means he's good...don't know, though.

Me thinks so too!!

Matt, please do post what all he does and says. I think we may need to get them out before we ever start building.

Ask for references, then call those people and if possible go and see their system.
Some of the local utilities also sell and install geo and/or might know an installer with good reputation and track record.

Well, that's interesting! Guess you don't need a septic tank?

By the way the house has most likely geo with floor heating.

Hey you guys....
Tell me about putting pex into a slab. I wanna do it with the shop area of our upcoming garage/apartment project. The entire garage and shop area is 28' x 44'. The shop portion is at one end: 28' x 27'. From what I'm reading, the correct procedure is to compact the gravel base and lay out the vapor barrier. Then, cover the entire slab area with 2" foam insulation (the pink stuff). Set the wire mesh on bar chairs to keep it centered in the slab and tie the pex to the wire mesh. Set the pex run to start and stop as close as possible to the hot fluid source and form out a small area in the slab to install the manifold. Pour a slab. I'm thinking 4" thick.
Thoughts? Tips?

Brettski,
I was looking for some more pictures, but I couldn't find the ones I wanted. This is one corner of my basement slab where I stubbed in for a future bathroom. Where there is no PEX is under the utility room. To the right side of the picture, you can see the pattern I used throughout the 30x60 basement floor. To cover entire area I used six loops, each about 200' long if I recall correctly. The wire mesh is 6x6, so the tubes are spaced about 12" apart. The blue vapor barrier has insulation in it.

What diameter pex is it? From what I've read, if I use 3/4" i.d. I can space it about 16". That would work great since a 500 ft coil would do the entire area in one run.

I don't think it is a good idea. You will have large temperature gradient between the tubes (the middle will be much colder. Also 1/2" is easier to handle. It is also good to have some built in a redudndancy for the case one of the loops gets damaged. Beside that you will save, in scope of things, negligible amount of money. There is also a plastifier (additive) to the concrete to make it better contact the tubes without bubbles and gaps. Didn't hear about it in the USA but we always used it in Europe.

Thanks Jersey
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Ladia,
That's the kinda input I seek. Thank you. Considering we are talking about a slab area of 28' x 27', what would you call a good idea for amount of runs of 1/2" id?

The general rule is to have all loops associated with particular manifold of similar lenght. I think about maximum 200-300 ft long. Some of the manifold (in ex. Rehau) have built in rotameters (flow meters) for each loop so adjusting the flow and balancing the loops is very easy. It is better to err on the short side I suppose. You can always limit the flow of short loop but not necessarily the other way around. As I said before I am just informed amateur so ask the proffessionals for second opinion.

Brettski:

Did exactly this for a 30x40 pole shed workshop for my best buddies ol' man. WORKS GREAT! Used 4 runs of about 300' each, 1/2" ID Pex, spaced at 12" OC...about 1 foot of tube per square foot. 300' per run is about max, otherwise you can't use the cheap (readily available) TACO brand, $100 pumps...not enough head to overcome flow resistance. Much longer and you have to step up to 3/4" tube and "High Flow" pumps.

We started 6" from ext. walls, and alternated flow (first run CW, second CCW, etc.) but you can do that with how you hook up PEX to manifolds. Just start wherever and make loops leaving enough tube to reach back to the start point. For us, it's all one "zone".

Not sure why folks want the manifold in a box on the floor...I mounted manifolds on the wall and ran tubing up to it, but it's a shop so we didn't care about "hiding" all that stuff.

Make sure your insulation is rated for below grade work, and High Density...AND make sure you insulate the heck out of the edge of the slab. We messed up a bit...snow melts away from the slab outside, so we know we're losing heat, but it still only takes $50-75/month to keep the place at 70F+.

We also used these plastic clips (google PEX screw clips) that twist into the insulation to attach the tubing. Laid out rebar on top of that...never have to worry about puncturing that tubing later as it's in the bottom inch or so of 5" of concrete.

All was bought locally at Menards...maybe a grand for everything, including the 50 gal gas HWH. I'm doing this in my shop this summer, too.

Had the first guy out to bid on this...may not need to have anybody else out...

He did all the right stuff...measured every window and door, square footage of house, took pics of existing HVAC equip, asked about fuel/elect usage, types/quantities of insulation, "any cold/hot spots?"...and was taking ALL THAT back to his (get this!) engineer to actually calculate what I'd need. They will work directly with local Elec coop to ensure I get an acceptable install to qualify for rebates and install separate meter to get lower rates.

We talked about arial pics (he says they usually have them, but they got left out of his "directions" pack) and I just emailed a link to 09/08 set so he can share them with his "dirt guys" to work out best package (which pond or use trenches).

Later, I was talking to the Elec coop guy and turns out they know these folks well...they recommend this installer to customers when they need troubleshooting done or just a third party opinion when there are performance issues. This guy was also expounding on the cost savings HE gets with his system.

Gaining confidence all the time...wife says this and the shop have to wait til after the daughter's wedding in May. Dang it...now I'm excited.

Thanks Matt,
Yeah, I did pick up on insulating the edge. I have a good link to a site that describes most everything you guys have pointed out, right down to the plastic clips that stick into the insulation.
I'm having a hard time believing that the slab (with the 2" hi density insul supporting it) would have the nuts to adequately support the weight of vehicles, trucks, and implements. It just don't seem right. I'm sure that upgrading to rebar would provide improved lateral distribution of the point loads, but is that the reason...or...is the foam really strong enough. Sorry, but I just can't buy it.

If you just make sure that your subgrade (stone, sand, whatever) is properly compacted and level, it has no problem supporting anything. My concrete guy suggested I add a couple inches to the floor in case I wanna pull the tractor in the shop. 7000 lb Farmall 560...

Type V XPS has a compressive strength of 100 psi. I'll probably go with Type VII, at 60 psi which is plenty strong. Tractor with concrete would only be about 30 psi or less...