Pond Boss Forums INTRO Questions & Observations Geothermal Heat Pump

If you have a radiant floor system, they recommend running all of your water through the slab before it gets heated. This cools the slab, which is "free" air conditioning.

Sorry I haven't gotten back sooner. I've been traveling for work. There is no issue with mineral deposits in the geo unit using as open loop. The entire system is pressurized just like your well pressure tanks. Mineral doesn't deposit in your well pressure tanks, the geo unit is no different. Minerals can only deposit when there is no pressure and the presents of air or oxygen. The valve that allows the water to flow through the geo unit is on the water output side of the plumbing. That way the heat exchanger and coils are always under pressure originating at pressurized well tanks. I use my homes normal well tanks for the house water as the geo water source. I tap is off the tanks before the water softener. As far as the well goes, I had to go deeper to get the quantity of water I needed for the geo units, and I has to add a couple of extra pressure tanks to make sure the well pump doesn't cycle too often. As an extra bonus, check out your local power company. Most of them have preferred electrical rates for geo customers, usually less than half what you normally pay. You will have to have a separate meter and electrical panel, but that cost is minor to the huge savings you get by using electricity to power the geo units. Because the well is now needed to run the geo units, the well pump can be tied into the separate geo electrical panel too, so whenever you use the well pump, even if it’s for the normal house water, you pay the reduced electrical rates. As an example, in Michigan the normal electrical rates are around $0.11 per Kilowatt hour, my geo rates vary by time of day anywhere from $0.07 / KWH to as low as $0.029 / KWH. As you can see, the savings is huge.

I also use the geo units to preheat my hot water for the house. I preheat up to 90F, and yes, your electrical usage is all at that reduced rate!

Great post, Country....it really opens up alot of considerations. Can you describe the "dumping" procedure of the waste water? How does the exit maintain the pressure...a check valve or sorts? and...how do you channel the water back to the pond; a below frost-line pipe?
Also, really curious about the water supply system setup. Specifics on the pressure tank sizes? The HP of the well pump?
Thx
Brettski

Since Country Boy brought up pressure tanks, this is off the geo subject but loosly related. The system we used has a tiny pressure tank. Only about 1 1/2 gal. It has a control unit that by the push of a button you can change your water pressure. You can crank it up until the pressure valve blows, believe me I know, and it comes with lock to prevent you from cranking it up too high, if you set it, don't ask. We can turn on every faucet in the house with no noticeable drop and the pressure is excellent. We have been plagued with poor pressure in other houses and this was a priority for us. Just something else to consider. Like there isn't already enough decisions to make.

Thanks for the posts guys, this has really got my squirrel cage a turnin'. I haven't had a chance to check on the flow requirements for our particular situation but one GT unit I was browsing claimed they ONLY used 2 cfm of water for operation or about 15 gallons per minute. I expect ours would be quite a bit more than that because the house is bigger than most of the case studies I've looked at. We have a separate pond water pump and pressure tank system and pickup already installed. I may have to draw off the pond for household water and just use the well for drinking water and the heat pump.Is anyone else set up for pond water household supply? Does the hot water side of the unit care where the water comes from or is limited to just the well source?
Chip

Here is a link to more information than I know what to do with:

Water Furnace Specs

I have 5 well tanks, one for each geo unit. Yes, this is a big house! Once the water exits the pressure valve on the output side of the geo unit, the pressure drops to zero, and it is a gravity feed out the wall of the house and flows by gravity in a 4 in" PVC pipe to the pond. It dumps above the surface of the water (important) at the edge of the pond. It doesn't have to be below the frost line because the water is always moving. It won't freeze in the pipe. I see on some of the posts that someone is using 15 gallons/ min. WOW! I think they must be quoting close loop anti-freeze flows. The nice thing about open loop is, because the water is both warmer in the winter and cooler in the summer than closed loop, you don't need nearly as much flow to get the desired effects. My basement unit is a 5.5 ton unit, and it has a flow regulator pegged at no more than 7 gallons/ min. A closed loop would probably be in that 15 gallon /min range to get the heat or cooling effects needed.

Think about some of the posts hear. Some are talking about the coils freezing into huge blocks of ice at the bottom of the pond in the winter. Well ice is 32F and your geo unit is trying to extract heat from it! Not that efficient. In the summer, assuming you aerate the pond, once it de-stratifies, will be in that 70F range (Michigan weather) and that’s your source of cooling! Sure, the geo unit uses a compressor cycle, but you need a lot of flow too achieve good cooling. Frankly for heating, I'd rather bury the coils 4-5 ft in the ground. At least there, in cooling mode, you can use the cool earth as your heat sink.

Of course, I'm a big open loop advocate, in the winter; my input water is 50F, in the summer, its 50F. For me it's the only way to go.

OK Country, your pitch is strong and definitely has my attention. My proposed home project is gonna be quite the opposite of your's. I anticipate a much smaller structure; a tight, efficient chalet looking over the pond. Size? Probably a 28' x 44'full basement footprint and 1.5 stories. With your exposure and background on the "pump and dump", can you dare a guess on possible equipment needs?...3 or 4 tons? I gotta guess that one sizeable dedicated pressure tank will git it...? I think my biggest fear of open loop is the water supply end. I keep thinking of a 1 HP 220v pump cycling every 5 minutes and the related energy costs and wear/tear on the pump. I am in a county that offers a co-op division of Touchstone Energy. I am going to reach out to ask about installation rebate programs and usage discounts, but I fear a midwest farmer community co-op will have little to offer.
Also, I wholely agree (or at least question, as noted in a previous post) that the consistent temp of a grade burial closed-loop is likely more efficient than temp swings of pond water; well water would naturally follow the same.
I like your thinking and appreciate your participation...thanks.

Your radiator type heat exchanger in your pond sounds like the same style as the slim jim which is metal and takes up very little space. I am trying to scan in all information but do not have it mastered yet.
The slim jim comes in different sizes for the various tons.
try http://www.awebgeo.com/SlimJim_Specs.asp

If I use an open system in my lake (I know I won't heat up 7 acres) how would I filter the water?

deaner,
That's exactly what I was looking for! Any idea what they cost?

Jersey
I went thru my file on geo thermal as I thought I had the prices, I am unable to locate prices. Telephone 1 888 277 2932 for prices. I discussed this with a lady in Louisiana that installed hers in a half acre pond but her house was well designed for effiency and the pond handled her unit very good.

Brettski, I'd go as big as you can afford. At least 4 ton unit. Much depends on how well the building is insulated as well as exposure, air infiltration, etc. The difference in cost between a 3 and 4 ton unit use to be only $300. As far as the well goes, I strongly suggest you consider 2 well tanks in parallel. Your well pump will cycle less often. Most all the wear and tear on the well pump is in the start up. Well pumps will typically draw three to four times the amps at start up. Put an amp meter on the power lines going to the pump, and you'll see. Any well installer will tell you that it's better to run the pump continuously with longer fill times, than constant cycling every 5 minutes. This cycling will eventually burn up the pump. The only way to accomplish that is to add pressure tanks.

Country,
3 - 4 tons of thanks! I have just spoken with the power company guru regarding geothermal. His immediate response was "if you can afford the upfront price, it is the only way to go". He went on to add: the only programs available is a $500 rebate on the system...nothing on the power rates. In fact, the current rate of .08 per kwh is about to top out at .09 in 2006 due to an increase. His only reservation about an open loop was the possiblility of the well drying up (thanks, but kinda obvious to me). Past that, tho, there are geo heat systems in the county and he pointed me to HIS guru at the power company...I have yet to call him, but it's on my list. btw, regarding the well, during my search for this property, I pulled the state well records. The 3 closest wells are all within 2000 ft and reported tests of 15, 15, and 35 gpm for one hour. This is a good sign?

Cut and paste doesn't work too good, but here is the spec sheet with prices. The model number shows how many tons it can handle in still water.

DESCRIPTION DIMENSIONS PRESSURE DROP VOLUME

SJ-02T 2’ x 6’ x 3/8” 6 GPM, Approx 5 psi 1.2 gal 55 lbs $ 1,486.00 28 lbs.

SJ-03T 4’ x 5’ x 3/8” 9 GPM, Approx 2 psi 2.0 gal 92 lbs. $ 1,991.00 46 lbs.

SJ-04T 4’ x 6’ x 3/8” 12 GPM, Approx 4 psi 2.4 gal 110 lbs. $ 2,195.00 55 lbs.

SJ-05T 4’ x 8’ x 3/8” 15 GPM, Approx 6 psi 3.2 gal 147 lbs. $ 2,736.00 74 lbs.

*SJ-08T 4’ x 12’ x 3/8” 24 GPM, Approx 8 psi 4.8 gal 220 lbs. $ 3,490.00 110 lbs.

a 3/3/06 dialogue, cut & pasted from another thread; transferred for continuity....
Brettski asks:
Ryan Freeze responds:

I noted (a couple of posts up) that I was gonna contact the local power company geo-guru. I did the end of Jan; some of the notes to follow.
Most geothermal (GT) in the area is closed loop, a few are open (pump & dump; P&D). The county will provide a $500 rebate for installation of GT unit. Also, the federal govt will provide an income tax rebate, based on a Bush bill signed in Aug '05. The state will also provide a property tax deduction. You fill out the forms once in the beginning and the deduction will be perennial. If I use a super-heater for the (electric) WH, they will provide the first WH tank at n/c and a 2nd (some folks do) at their cost. (They are a Touchstone Coop)...no breaks on electric rates regardless of loop design; first block is .08 kw/hr (smaller, usually consumed by lights, refrig, etc) and second block is .065 kw/hr. They feel this second block is reasonable and provides rate relief for the additional cost to run a 220v well pump to power a P&D sys. He noted that there is plenty of water in our area; an open loop should be no prob. He noted that an avg home sys requires 6 gpm min for GT on P&D (personally, I think this is kinda slight but I think he considers avg home as smaller).
I have already pulled the well records for 4 v recent wells, all within 2000 ft of our project. It should be a non-issue. I continue to lean toward P&D.

Brettski, Mid American currently cuts our Electric rates 50% from Oct- Mar,then holds at normal rates for the second six months of the year when using all electric in my home. I believe you will be very happy with the results of either the P&D or the closed loop. Sounds like some great incentives Good luck!

I just did a figure on the pump and dump and I believe my pond would hold this since I have good evaporation. The pond gets very hot in the summer so a closed loop would require a much longer run time. I find each of your thoughts very interesting ---thanks. I have a high capacity pump so 2 more tanks would decrease the run time sufficiently.

Is your pond spring fed or does it have a lining. If it's spring fed, the pond can take any amount of water you dump to it. The hydrostatic pressure of the pond equalizes with the pressure of the aquafer. In my case, I put in a winter heating season, over one million gallons of water, and my water level went up 3-4 inches, then stayed there. If the pond is lined, it's like a bath tub, so all the water you dump to it will raise the level, unless you have an overflow somewhere.

My pond is clay lined and I have a pump rated at 60 gallon per minute. I loose about 2 inches per day more or less because of evaporation. My pond held on fillup approximately 2 1/2 million gallons of water and we had a very big rain at that time also. I have a dip in the berm where it could over flow if needed. on a refil the other day I pumped for about 26 hours or 9360 gallons unless I figured incorrectly.

This is a really long post - sorry. Don't get me started.

I do Geothermal. In response to Brettski's request I am posting re:geothermal heating and cooling. I have been an HVAC contractor for over 25 years and we put our first geothermal system in about 22 years ago.

Some of the prior information is good, some not. A geothermal system first of all is not really geothermal - technically. A true geothermal system would be one that uses heat from deep in the earth, like the hot springs in Wyoming. A more accurate description is Ground Source Heat Pump. Not as sexy, but more accurate.

As Country Boy pointed out there are 2 types commonly installed - open loop and closed loop. Open loop is also known as "pump and dump". Open loop extracts water from the ground - then either absorbs heat from it or rejects heat into it - then dumps it. Closed loop systems circulate water (with antifreeze in it) in a closed loop in the ground. The water leaves the house and the fluid either absorbs heat or rejects heat depending on if you are heating or cooling.

All of my experience is with closed loop systems. Around my part of Ohio, it is not unusual to have problems with water quantity and/or water quality. If the water has iron and other stuff it it, maintenance of the water pumping apparatus is an issue. If you do not have enough water in gpm year-round, the system will not perform properly. We like closed loop because we avoid those issues. Not saying they won't work - I am guessing maybe 10 or 20% of installed systems are pump and dump - I just do not have any experience with them.

Closed loop systems can use a ground loop that is either horizontal, vertical or in a pond. (magic word - give that man a cigar). We have installed maybe 150 systems. Most have been horizontal as it is the least expensive to install. We use veritcal when there is not enough room for horizontal or the owner doesn't want us to mess up his yard too much. Ponds work great if they are big enough and not too far from the house. 200' from pond to house is a good number but it is always possible to go with bigger pipes and pumps if the pond is farther away - just doesn't always make sense economically. All 3 methods - horizontal, veritcal and pond if installed correctly will work just as efficiently.

Regarding the sizing of the unit - how many tons - that is not a casual consideration. We always use an industry approved method to size the equipment - ACCA Manual J - to see how much heating and cooling is needed. A smaller well insulated house in Illinois would not necessarily need a 4 ton system. More on this if you want it but I think you need an HVAC contractor who will calculate what you need and stand behind it (that is what we do). Let me know if you need more info on correct sizing.

We install WaterFurnace brand systems. We always install polyethelyne pipe for the ground loops. We have a special "iron" that melts the plastic and welds it at the joints - stronger than the pipe (burst). We test our installations as we put them in. Never had a leak. I would never use copper due to potential for leaks and future corrosion. Polyethlyne is the same stuff as garbage bags. Dig it up 40 years later no deterioration. As long as Polyethylene does not see UV rays it is the way to go. Priced copper lately? - they are stealing it as fast as we put it in.

As far as is it the way to go the short answer is yes. This is what I do for a living. I can give you the algebra formulas to compare all the different options you might consider for your home. Geo wins every time. Some examples"

Natural gas w/90% efficint appliance and $10/1000 cu ft = $11 per million btus into the house.(Nat gas wes 50% higher than that last winter in most markets).

Propane gas w/90% efficient appliance and $1,75 per gallon = $21.25/million btu into the house. (they are at about $1.99 per gallon locally here).

Fuel oil - 80% efficient - $2.50 per gallon = $22.32 per million btu into the house.

Electric reistance heating (elec baseboard, elec fan forced heaters, electric water heater, toaster, hair dryer) - if wither electric costs $.06 per kWh (local rates) = $17.58 per million btu into the home.

Geothermal (Ground source heat pumps) deliver 4 times the heat for one kWh vs. elec. baseboard, or a per million btu into the house cost of less than $5!.

As you can see, local costs for the electricity and the various fuels plays into it, but no matter how you slice it ground source heat pumps heat for less. Oh yeah, they also cool for a lot less - very important to our southern friends. Oh yeah, they also typically produce about 50% of the energy needed to heat water (at 25% the regular cost).

There are of course a lot of other things to consider. What is the "upfront" installed cost of the various choices? What local fuels are available? (nat gas not available in all areas). What is the energy load of the building ( a small load that does not use much energy reduces the effect of more efficient choices). Does the homeowner want air conditioning (believe it or not we have customers who do not want A/C. This reduces the value of geo as it is a heat/cool system and it uses rejected heat in the summer to heat domestic hot water). Do you want a tank (LP or oil)? Do you want combusition and the possibility of CO (Carbon Monoxide)?

And now the really serious stuff. What is the maintenance cost? Oil is an annual affair to keep it running efficiently. LP and Nat gas burn cleaner but still require regular maintenance to keep efficiency up and avoid repairs. Geo units are pretty much "plug and play" if designed and applied correctly. Kinda like a refrigerator. Or driving your car at 55 all the time. When we do "annual maintenance" on our geothermal installations, it is like going to the doctor when you are not sick. Check - ok, check - ok, check - ok ,etc. etc. Other than keeping the air filter clean, there is nothing to lubricate or adjust. So "life cycle costs" are much lower with geo.

Lastly - what is the outlook for energy costs? We have seen big run-ups in cost for fuel oil, LP gas and natural gas. Electricity, which used to be considered "expensive" to heat with is now suddenly an option worth considering. What does the future hold? Well electricity is generated mostly from coal which has nearly doubled in cost in the last 2 years (wholesale market). Most electricity generators and resellers are tied into long-term agreements that slow down their ability to raise prices quickly. But increased electric costs are coming. The electric utilities have a product that costs them more to produce, and the customer's other options have increased dramatically. They will be raising prices as soon as the regulators allow it.

So there you have it. Geo 101. Feel free to ask other Geo or HVAC related questions. I will help if I can.

Bravo Asleep...Bravo!
Very educational. I believe that you will find a very interested following within the PB forum. Many thanks for the dissertation.

Thank You AaTW. I am very interested. Is the system less efficient in a HOT part of the country like Texas? What are the up front cost caparisons? Do you drill a well? How deep? How could a horizontal loop help when the ground is 90 degrees at 10' around here? (may be an exaggeration but it is hot).

PFF - geo is very popular in Texas and very efficient. Geo will cool your home in Texas using a lot less electricity than a typical air-source unit. If Bruce ever sends you 12" Bluegill I want some too.

The up front costs to install geo are higher. The systems we put in are usually 3-5 tons for homes 1500-3000SF. Usually about $15K to $25K total for HVAC system installation but there are a lot of variables. - we sometimes do zoning, air cleaning, swimming pool heat, radiant floors, etc.


Air source heat pumps are very competitive with other choices ( I prefer them over gas and oil and I own one - yes they work great north of the mason-dixon line). A geothermal system costs probably about $5,000 to $10,000 more than air source (or gas or oil). If you are building with a 30 year mortgage the upgrade will cost you maybe $40 per month on your loan payment. It will save maybe $60-70 per month on utilities. Black ink from day one. You can make this analysis as complicated as you want. Black ink from day one is a reality.


If you are considering retrofitting with geo we charge more for that - it just take more work. A geo retrofit for a 2500 SF house might cost $15-20K. Often the electric service needs upgraded to 200 amps at additional cost ($2K).

I have found people get all hung up on the upfront cost and can't see the operating cost pays for it.
If you pay $500 for a refrigerator and a more efficient model is $800, and the lower cost model uses $1500 more electricity over its lifetime (about 20 years) which one is cheaper?

PFF - you can find out what the average ground temp is at 5' depth by asking your local HVAC contractor. You will have to ask someone else about drilling a well - my experience is with closed loops - no well required. If you are serious you need to find a local HVAC contractor with experience in geo. One way is to go to waterfurnace.com and select "dealer locator" or something like that.