Ground water heat pump?

[techman]

Ive heard of dual wells, pump ground water up, circulate it and pump it back down into a second well a few feet away from the first.

That is called an open loop system. While they can have the highest efficiency, due to constant water temps, issues with water quality and contamination result in much higher service and callback issues. I will not install them for that reason. If you need to spend the money drilling, I would recommend closed loop in bore holes (drilling).

Ponds with closed loop coils work well also, assuming the pond is big and deep enough to handle the heating and cooling loads.

paul

 

[pennwalk]

Thanks for the web sites. I haven't sat down and done my homework yet.

All our proposals were for closed loop systems in wells. That is probably just as well as we live on a hill and there is only six inches to a foot of soil over the rock. I remember when the excavator was chiseling out the basement for the house next door. They hammered and dug for days. I think digging trenches here would be a job.

For you guys in the business have your prices gone up a lot in the last two years?

Chris

 

[gkharvey]

Someone brought up water quality----need to make sure quantity and quality are suitable. we had one sourced by our well; we had plenty of, but not good water. It was efficientl but had to be cleaned annually as inside of pipes became foul. we switched to a ground loop closed loop system in 2001. works great with 50% windshield solution in lines. three ninety foot trenches do the trick here in Michigan with 52 degree ground temp. we heat approx 2700ft. total electric was $112 monthly three years ago, increased kilowatt cost has us up to $151 last year; (we added as three season room which would be eficient we could rotate our house 180degrees. but the wife is happy......) this I think drove our heating cooling up.

if you slept through 7th grade science class, you need to go back and take it over again; awake!.

 

[KentT]

Ponds with closed loop coils work well also, assuming the pond is big and deep enough to handle the heating and cooling loads.

paul

What kind of depth is required? My property fronts on a 6-acre pond, but along my shoreline (I actually have deed to 3/4 acre of land under the pond) the pond is shallow due to silt buildup. I'd guess no more than 6 feet deep at best, with many spots being 3 feet or so.

 

[techman]

For ponds, a minimum depth of 10' is recommended. That is the minimum you would want. The temperature gradients become and issue if it is any shallower. Size is also critical so as not to allow it to freeze.

paul

 

[techman]

three ninety foot trenches do the trick here in Michigan with 52 degree ground temp.

I am not sure if you have your facts right. general rule of thumb is 500'/ton of piping. With the short trench you mention, it is most likely a "slinky" of tubing in the trench, with a considerable length of pipe. Also ground temps you mention are nominal. Seasonally they will vary +/- 10~15 deg just due to the ambient temps. Add, or subtract from that the local change due to the heating of cooling you are doing to the ground and your loops will vary between 35 and 65 deg. The ground is actually a poor conductor of heat, so the system will additionally warm or cool the ground around the trench. This is why the antifreeze is needed in the loop, to prevent freezing in the winter. This is also why closed loops are less efficient than a pump-and-dump well system, which will only vary a few degrees in temp, from around 50 deg F.

paul

 

[heehaw]

with a "pump and dump" system, aren't you using a lot bigger pump to circulate the water? which would increase the cost of operation?
heehaw

 

[heehaw]

("ive even heard of people useing a bypass meter on there water service. you use the existing municipal water pipes as your loop.")
i don't think that would work to well in Arkansas: our municipal water gets pretty warm in the summer and really cold in the winter.
heehaw

 

[techman]

On a pump-and-dump the pumping costs are generally quite a bit higher. You are paying the cost to lift the water from the level in the well. On a closed loop, the pumping costs are the losses in the piping, which if properly sized are small. My own closed loop pump uses less than 100 watts

As far as using city water, that has to be pretty costly. At an average of 3 GPM per ton, 9 to 12 GPM is typical. That is a lot of city water.

paul

 

[heehaw]

my wifes uncle had a pump and dump geothermal system for many many years: it was finally replaced about 3 years ago with a high eff standard heat pump: and according to his wife, they're electric bills went down a lot with the new system. thats why i thought the well pump would raise the cost of operations quite a bit: i figure he had at least a 1.5 hp pump: maybe a 2hp.: that would drive the cost up quite a bit.
heehaw

 

[KentT]

For ponds, a minimum depth of 10' is recommended. That is the minimum you would want. The temperature gradients become and issue if it is any shallower. Size is also critical so as not to allow it to freeze.

paul

Thanks for the input. I think you just ruled out that possibility...

 

[heehaw]

several years ago i saw an add on device to help reduce air conditioning cost: this wouldn't work for heat, but: its a solenoid you put on your compressor, so when the compressor comes on, it opens a fine mist watering system to spray water on the coils: if your on a well, that would be pretty cool water, which is basicly what a geothermal system does: has anyone seen or tried anything like this?
heehaw

 

[mahlers]

What you're describing is basically the concept behind evaporative coolers (swamp coolers). They do work well. As water evaporates, it cools down because it takes energy to transition the water molecules from a liquid state to a gas state. That energy comes from the ambient air or the surface being cooled. Of all air conditioning devices, the true evap coolers are the most efficient - but they only work well in a very narrow range of conditions (right temperature and humidity). The downside is that your water source needs to be really good - well water is usually bad because it contains so many minerals. As the water evaporates, you'll get a layer of minerals all over the coils, which in the long run will lead to poor efficiency and an expensive repair bill. If you run the water through a reverse osmosis filter setup to take out the minerals, this should work pretty well.

 

[schmism]

As far as using city water, that has to be pretty costly. At an average of 3 GPM per ton, 9 to 12 GPM is typical. That is a lot of city water.

paul

your not acutally using the water.... it runs to a coil and back to the main. (heat exchanger is out by the water meter)


as for the comment of "warm water in the summer, cold in the winter"
as long as the water is above freezeing and below boiling (at the elivated pressure your running at) then your system will still "work" may not be as efficient as it could be with good temp gradients, but it would still work.

 

[KYErik]

your not acutally using the water.... it runs to a coil and back to the main. (heat exchanger is out by the water meter)

I am surprised at this possibility. I know the water lines are always under pressure so it would be hard for a leak in your piping to contaminate the neighborhood water supply. But- since you and your neighbors are drinking the water that goes through the heat exchanger- wouldn't the heat pump heat exchanger, solder etc. all have to be NSF approved for potable water?

I think this would make many neighbors nervous.

Do you just pay for two water meters on your property and run one backwards? How else would the water company be able to charge you for any leaks in your piping?

 

[mahlers]

I don't get how this works. Since you're taking water from the main, and then putting the water back into the main fairly close to where you took it, it doesn't seem like you'd have enough 'fresh' water to provide reasonable heat source. It seems like you're just circulating the same water around - unless you are using a LOT of water continuously or your water meter is a few thousand feet from your house.

Also, all of the utilities I've ever dealt with wouldn't even think of allowing someone to tap into their water main before the water meter - that part of the main is their property and they don't take kindly to people messing with it.