Pond Boss Forums AERATION Should I aerate? Aeration and Geo-Thermal

Ben looking through the archives and still can't seem to find a definative answer. So I'll ask the question.

Can you install your loop in the pond if it is aerated.10acre pond 20' depth at dam.

House not built yet and no aearation,Just in the planning stages. Thanks

We are close to making a decision on a geo-thermal system, so we've done a lot of reading and questioning. At least from what I know, I see no reason why aeration should affect the loop.

On a somewhat related side note, each of the contractors we've talked with feel that we would have a more efficient and less expensive system by going with drilled wells rather than using our pond. Part of it is that the pond is about 500 feet from the house.

I have a closed loop geothermal system with coils in my pond. Installed it two years ago. Here's some lessons I've learned:

Water-flow around the coils is VERY important. Originally we buried 4000 ft of coil in the base of the pond. The thought was, we've already got the hole dug (the pond was new), if a horizontal loop normally works fine in 4-5 ft of dirt, surely, lining the coils on the bottom of my pond, 8 ft. down, should be fine.

The pond is lined with rubber, the heat pump coils on top of that, and then 1 ft of pea gravel. We have a 5-ton heat pump. When we finally got around to connecting everything it was late October. We fired it up and the thing froze out in about an hour, even though the pond water was 50 degrees. We couldn't use it all winter long. Every time it froze up within a short time.

Last summer I spent 30 hours with scuba gear unearthing the coils. Water is a great source of heat storage, but not necessarily a good heat exchanger (think thermal layers). I put one of my two air-diffuser aerators right in the middle of a bunch of coils.

Today, it works as designed. My incoming water temperature is constant. I can run the unit for hours with no drop in entering water temperature.

Another point of caution. There are metal plates that can also be used instead of thousands of feet of coil. I've heard that these have a real tendency to ice up. There again, however, it is likely a water-flow issue around the plate.

Also, the efficiency of heat pumps varies greatly by the entering water temperature. What I have come to realize is that during the winter when my pond water is in the 30's, it is more cost effective to run natural gas.

In retrospect, I wish I had installed a closed ground loop rather than a pond loop where I would have a constant 50-degree ground temperature. My heat pump is 50% more efficient with 50-degree water than 35, and I have very little use for heat when my pond is 70. Ask the heat pump sales rep about COP levels based on entering water temperature.

Lastly, you have to watch snagging the coils while fishing.

Tim -- great post. Thanks. It makes me feel a little better about going with the ground system. We have constant ground temperature of around 55 degrees, and my pond ranges from about 35 to 85 degrees -- at the wrong times.

Ken

Thanks Guys,
Just gathering as much info as I can. I havn't spoken to any factory reps or local HVAC guys.I'm still at least a couple of years from any action.

Iv'e got plenty of room to go horizontal or vertical. Sure would make me kinda nervous drilling a vertical well next to my pond. Anyone else have issues with that or is it just me?

I did have a lengthy conversation with a HVAC testing and balancing guy on a large school project and he said if I really wanted to have the cat daddy of effieciancy combine the geothermal with an outdoor wood burner and LP backup boiler with the hot water coils poured in the pole barn floor and the subfloor of the house.Obviously alot of front end cost but I'm a big DIY'er so we'll have to see at that point.

Thank's Again Rob

Ken & R&R, have you thought about an open system, dumping the water into the pond? Getting the water from ground water sources (i.e. well) and dumping it into the pond?

I know Cecil does that, and I was looking into that type of system for the house. I have a friend that has that type of system and he's been happy with it for the past 20 years.

Dwight has a closed loop system that uses coils on the bottom of his pond and IIRC it works without turning on the electric 3r stage in -40°F weather and howling winds.

You might want to read this thread Windmill Aeration & Geothermal Pond Loops and/or contact MarkECIN about aeration and geothermal.

esshup I would assume it would be dependent upon enough volume in the well. But might be another option.
When I get closer I'll definatly talk to several contractors about all my options. Thanks

JHAP, Good read, Definately makes guy think twice about loops in the pond.Regardless of aerating or not. Thanks

R&R, you'd be suprised on how little of well water volume you need. I think the system that was spec'd out for me was less than 4 gpm.

esshup, Can you drill a well too close to your BOW?

Good question! I don't know. My house well is roughly 100' from my pond, and I was thinking of sinking one within 20' of the pond to use for irrigation and to replace water in the pond that is lost to evaporation and leaks (sandy soil).

An open system of drawing from the well and dumping into the pond is a great solution provided you have an adequate well to draw from and a pond that can support that kind of supply. If using for air-conditioning, then you have to consider the water supply at all seasons of the year.

My 5-ton (60,000 BTU) furnace requires at least 7 gallons per minute. At 7 GPM, powering a 60,000 BTU furnace, you'll be sucking about 17 degrees of heat out of the entering water. As long as your well water is 50+, you will be fine.

I think a heat pump is an efficient way to go. Just make sure you have a reliable backup. I have natural gas to back up my system, and actually ran gas through the winter because it was more efficient to do so, as mine is a closed pond loop that provided 34-degree entering water into the heat pump in the dead of winter.
-Tim

would it be correct to assume that you wouldn't know your GPM until you drill the well?

Correct, but a local well driller that has drilled numerous wells in the area might know before even stepping foot on the property.

I'm glad to see that someone mentioned the open loop system. When my wife and I looked at updating our system, we considered closed loop, air to air exchange, and open loop systems. After crunching the numbers we decided to go to an open loop system. A lot of that was due to the ease of trenching the outflow pipe to the pond as opposed to burying loops in the yard. It was significantly cheaper. We have been very happen with our system and have saved the cost of the system back in lower electric bills in the 10 years we have had it. It helps that we get discounted bills for being all electric in our utilities, but even without the discount, we would have saved the cost of the system. good luck on your choice.

I'll concur on the open loop system. We have a pond and have an open loop system that pumps from the well and discharges into the pond (or sprinkles the yard, depending on the time of year). It was way cheaper than putting coils in the pond and has been working great for us. Our house is ~1800sf main floor and I believe we are using around 5gpm. The beautiful thing about a pond is you have a no-nonsense place to discharge the water without the need to drill a return well.

Nebucks and straw, Thanks for the input. Not really up on the geothermal so I'm still in the "way in advance" planning stages. I'd assume that the cost of running a well pump vs a circulating pump on a closed loop would be about the same?

I have plenty of room to do trenching or the well. So it would seem that installation cost and efficaincy would be the biggest factor.