geothermal heating/cooling

Thanks

Steve

Is it really feasible to install geothermal yourself? My wife and I are building a home here in eastern WA and had considered geothermal but the installers areound here want like $10,000 more than the cost of a conventional air source heat pump. We are building most of our home ourselves anyway, and would be up to the challenge of doing the geothermal install - although a lot of the websites on geothermal seem to indicate it's not a job for the do it yourselfer. Our house will be a 2500SF cape cod style floor and a half.
We already have a dry well hole (well driller hit a cavern at about 260' or so before getting water on the second well hole at 15gpm) so i thought the dry hole might serve as an injection well for an open loop system. (Would like to out it to SOME use since we had to pay for it too!)

rcnut,
I am certain that if you are building your home yourself you have been told numerous times there are tasks you cannot do. To me that just makes me more determined. I would think the same goes for you. That said, the most difficult portions of the installation are two parts. You need a good duct system as with any central system and second you need to deal with the loop. On a water well system there is no difficulty with the later. However, I strongly suggest you use a ground loop. The overall maintenance and operating costs are lower. As with the former; duct work, it is the same as for a conventional system of which both need to be designed to the application. Possibly you could hire this portion. With the duct work in place and using a water source the installation on a scale of 1 to 5 with 5 the most difficult it comes in at a 2. There are no freon lines to connect/install. To break the task down, you will need the unit secured to the duct, then you do a minor amount of plumbing (all PVC) to plumb the incoming water to the heat exchanger and then the exchanger is plumbed to a solenoid valve/flow meter that is easily adjusted then dumped to outside. The unit does not have to have strip heat to meet code here so the electrical connection is minor. Hooking the thermostat is a matter of following the color code and connecting a half dozen wires in the pre-existing box. You will have to plumb a condensate pump to remove the water dripped when in AC mode and run the line for the water to outside. The condensate pump is prewired and preset and has a 110 volt pigtail requiring no expertise. The you are DONE! You see anything complicated? I don't.

agmantoo
Thanks... some questions:

Size - I have heard you can roughly figure a ton per 700SF, is that correct? Our house is about 2500 sf, although we plan on conditioning the crawl space. (No basement).

Zones - is there an easy way to create a zoned system? That is something i have no clue about. I would have thought you just close off the vents more in areas that don't require as much heating/cooling? I am guessing you would have to have separate duct systems each with their own blower or something?

Closed loop - Would we would need glycol in these lines? I think the geo installers in our area are using some sort of refrigerant in the loop. THat was one of the things that attracted me to the open loop, you didnt need to deal with that stuff. Although I can see you point about the closed loop being less maintenance - our water is probably going to have some degree of mineral content. The well guy is coming out next week to test that.

Closed loop - how close to the house? We have some rock in the ground, if we could go further out we could be in farm ground that is good dirt and minimal rock.

Duct work - we do have a friend who does ductwork so I think that part won't be a problem.

THanks again, I appreciate your willingness to divulge the secrets of this "black art"

rcnut,
You need to call your utility company and request that one of their heating/cooling engineers contact you to schedule a visit to your site. He will have knowledge of all the incentive plans that the utility company has, he can tell you if your state will give a tax credit for energy conservation and he can advise you of the BTU requirement for your specific area and home design based on insulation, windows, doors, orientation, etc. My own findings are that you will not need as large a unit as typically is recommended for standard heat pumps.
A closed loop usually does have some type of solution that will prevent freezing and corriosion. There are enviromental friendly materials available but I am not current on these. That is something that I will have to research when time comes for me to replace my water feed system.
The distance the loop is from the home is nearly inconsequential and at the depth it will buried you should be able to ignore it once installed. Too much loop is the side to error on here. The loop itself should have a 50 plus year life.
My well water has a high iron content but the heat exchanger I have has an alloy (maybe inconnel) that expands and contracts with minor water temp changes and this causes the deposits to flake off and flush through the system. I neglected to mention earlier that a water feed system needs the water to be free of grit or sand as the abrasive materials will eat the seat from the solenoid shutoff valve. You will also want to install a large baldder tank on your well system. These geothermal systems use a lot of water(8gpm here) and the small contractor type tanks will constantly fill/empty and the well pump is off/on too rapidly causing the utility bill to be higher and the pump motor short lived. I never see geothermal installers addressing this issue nor the sand.

You might want to consider 'ground tubes'. Here's a link to a site explaining them in more detail....

http://mb-soft.com/solar/saving.html

I will be trying them in the house I'm renovating. (In fact, if it hadn't rained today, we would have started installing the pipes.)

This seems like a much simpler idea and not as dependent upon technology.

I had some other sites bookmarked but can't find them right now...

Thanks barbarake! THat is a very interesting link, similiar to geothermal but a lot simpler! I wonder how deep in the ground the pipes would have to be? Geothermal systems seem to stipulate 6 ft. How deep will yours be?

My pipes will be about three feet deep in the ground. I'm sure deeper would be better but it's a question of *how much better*.

The pipes are being laid in the septic trenches. The trenches are six feet wide and each trench will have two septic pipes and two ground tubes - so the ground tubes will be two feet away from the septic lines. Remember, the ground tubes are sealed - moisture shouldn't get into them underground so the septic lines are not a problem. But the septic lines should (theoretically) keep the ground a little moister than it would be otherwise - and that should dramatically help the performance of the ground tubes.

My additional cost to try this is almost nil since I have to have the septic dug anyway. Just the cost of the pipe itself and one additional trench dug to the house.

The air will be pulled through the ground tubes and collected into one main trunk. Then the trunk will split into different lines going to a vent in the floor of each room. The vent will have a cover that I manually open/close.

On the other side of the room, there will be a vent in the ceiling (also, manually opened/closed). Tubes from these ceiling vents will join to a main line and then be vented from the house.

First I will see if simple convection will provide cooling. (Is convection the right term??) In other words, as the house heats up in the summer, air will rise. It would go through the ceiling vents and then outside. This will pull air in through the ground tubes and through the floor vents. This may or may not work.

If that's not enough, I'll try a solar fan. And/or an electric fan. I'm sort of experimenting.

My house is small (1,450 sq. ft.), single-story and there's anywhere from 2' to 8' under the house to work in.

I'll keep everyone updated but it probably won't be finished for several months (since I have lots of other projects that need to be done first).

Hi all - Well, I actually got the ground tubes in the ground this past week. Made a couple of modifications as I went along.

One of the main things I've worried about with this whole setup has been condensation in the tubes and future mold problems. I've read that sloping the tubes and providing a way for the condensate to drain out is the solution.

I have four main pipes, all around 100 feet long. They gently slope to where they all join together. Then the main pipe rises fairly steeply to the house. So - where they join (i.e. the lowest spot) - I installed a 'T' with the opening facing down for drainage. Right next to is a 'T' facing up. These are both in a cement block 2' by 3' 'box' whose top is just below ground level. The 'T' that is facing down also has a 4" hole cut in the top so I can physically look at it. These fittings are not glued together so I can adjust them a bit if necessary. The cement block 'box' is lined with wire screening at the bottom.

I also threaded a long nylon rope through the four pipes (a separate one for each pipe). The ropes comes out at the end which is above ground and also through the opening of the 'T' that faces up (and then simply stay in the cement block 'box').

With me so far??

So here's my plan. I can physically examine the low spot to see if there's any water. I can also tie a towel to each rope and then add a second rope so that I can pull a towel back and fourth through each of the four tubes. This would sop up any excess moisture and also allow me to check for mold in the tubes. I could also disinfect each tube by disconnecting the 'T' facing down and capping the tube. Then fill each tube with bleach/water (or some other disinfectant) from the other end, let it sit and then uncap it and let it drain into buckets. (Am still doing research as to what disinfectant to use - any suggestions would be helpful.) When it's drained, dry the tube with the towels and it should be ready to go.

Any comments/suggestions would be appreciated. But remember that I'm sort of doing this by the seat of my pants so ... be kind.

installed a loop this year as an experiment - haven't tried it out yet - put the tube array in the form of a loop with EVERYTHING sloping to a low point - put a hole at the lowest point for a drain over a 2' by 4' hole filled with gravel - figure if mold or mildew becomes a problem i can go to any point at the high end of the loop and dump in a bucket of bleach water or lysol water - time will tell

The ground source heat pump loops are not normally meant to be drained, cleaned or exposed to atmosphere. There is no need. The loops should be sealed and not drained. If any of the system is exposed to freezing temperatures (or could be in unusual circumstances) then use a food grade anti-freeze in the system.

Mold will not grow within the sealed pipes. Water will not condense on the outside of the pipes if properly insulated. If water does condense and drip onto food sources, then mold could start to grow. Therefore, if you use your heatpump to heat as well as cool, then you must insulate all of your condenser and well pipes if they are exposed to areas that have moisture in them.

The condenser and well pipes will not condense in the summer because then they are hot. However, if you distribute water from the heatpump (use it like a water chiller) then the chilled water pipes will condense because they are usually operating at about 45 F, so they must be insulated for summer cooling operation.

The sloping and ropes and concrete and bleach and worry about mold are unnecessary complications. However, if you have a need to do this then that is what you have to do. I do not understand why you are doing what you describe. There are many ground-source-heat-pump installers in the USA, Canada and around the world that can help you with this.

Diagram of geothermal system, the ideas are applicable to single family residential systems.

The project shown in this link is a social housing project in Vancouver, it could supply cooling and heating and is set to only supply heating at the present, 16 houses (96 units - social housing) in Vancouver heated with ground source heat pumps.

Keep it simple (please no comments about this statement - if you can help it).

Alex

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alex - your comments are 100% correct if the heat transfer medium in question is liquid - however, the medium can also be air and, with air, condensation can be readily assumed - whether it results in a problem is a case by case situation

If the condenser only has air across it then the system is a more conventional "air to air" or "air to water" heat pump system.

An air to air system will condense (heavily at times) in the winter and must have provision for condensate removal and you must make sure to drain the fluid away safely. This type of system is subject to "freezing-up" and requires supplemental heat during defrost.

Alex

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Alex - I'm sorry that I didn't make it clear that I was (in effect) continuing a discussion from the previous page. The link I posted earlier might explain things better.

http://mb-soft.com/solar/saving.html

This is not 'geothermal' although the theory behind it is the same. I'll call what I'm speaking of 'ground tubes'. It basically involves pulling in outside air through tubes in the ground (thereby heating or cooling it depending on the season) and then into your house. The link explains it in much more detail.

From what I understand, ground tubes mainly have the problem of condensation in the summer since the air is cooled as it goes through the tubes and cooler air cannot hold as much water. That problem should not exist in the winter (since the air is being warmed as it comes through the tubes).

My comments might make more sense if I had explained better exactly what I was discussing.

P.S. I'm not quite sure what you're referring to when you say 'freeze-up'. Could you explain that a bit more so I can tell whether it's applicable for this situation?? Thanks.

Joan (and others),

The system you are thinking about, or have, or are discussing seems good and does not belong in a discussion about ground-source-heat-pumps. The link you posted is interesting and good, all except the divorce part.

If you do not have a compressor in your system, then you do not have a freeze up concern. The closest thing is the condensation in your air ducts.

In the winter an air to air heat-pump or reverse-cycle air-conditioner cools the outdoor air where the condenser section of the heat-pump is located. If the cooling temperature gets below freezing, and there is water vapor in the outdoor air, then frost can build up on the condensing unit coil (just as it can build up on the inside or evaporator coil in the summer inside, if the refrigerant temperature in the coil gets too low - due to various things, like too low refrigerant, etc.).

If you get too much frost, then the coil is blocked or "frozen-up". Then you have to defrost the condenser coil by switching the unit to cool the inside for awhile, and heat the outdoor coil, then you need to have extra heat in the inside or you will get too cold for awhile.

Alex

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My well water is 80 degrees constant so I was told geothermal cooling with it is not a good idea. What do you guys think about me using geothermal for heating only then? How would it's cost compare to heating with propane?

Both heating and cooling will work OK with 80F water from a ground source heat pump system. If you use an air to air heat pump or regular AC unit, then the condenser will operate at the outdoor air temperature. In your area the summer outdoor air temperature is much higher than 80, right?

Alex

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Brad - I would think your 80 degree water would work wonderfully for heating but I'm not so sure about cooling. Well, it probably would help some but it's a question of money, etc. Of course, if there's no additional cost incurred for using it as cooling, what can it hurt??

As to the cost versus propane - it really depends on exactly what type of system you're talking about. In general, I've read that a true geothermal system is relatively expensive to install and the payback is relatively long-term. But I'm pretty sure those installation costs involve drilling holes which evidently you don't have to do since they already exist(??).

My 'ground tube' system is costing me very little since the digging was already being done - my only extra cost were for the actual pipes/fittings (I did the work myself). So it was worth giving it a try. I probably would not have spent thousands of dollars to try it.

There are a lot of variables involved - and costs can vary dramatically from one part of the country to another.

Why don't you give us a bit more information about your situation and exactly what you'd like to achieve - I'm sure you'll get more input then.

Well, I have one good well that produces about ninety gallons a minute. After thinking about this I probably wouldn't want to have to put more wells in as it is expensive to drill here. (25 bucks plus a foot) I am wondering if there is such a thing as an air conditioning unit with a water sprayed condensor to help cool it and thus make it more efficient? Perhaps the spray could come on each time the unit runs?

Alex: It does get very hot here with many months of the year over one hundred degrees.

An evaprative cooler or "swamp cooler" system, possibly combined with mechanical cooling of some type (heat pump etc.) should be very efficient in your area. The capitol cost is low, as well as the operating cost.

Check with you local evaporative cooler supplier.

Alex

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