whistlepig
Elite Member
The pond would have to be large enough that it doesn't freeze solid. Pond loop geothermal will work at a water temperature as low as 35 degrees.
geothermal pond loop?
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bdw593
Bronze Member
I just got done building a house and looked into the pond loop... Ended up going with the geothermal but went with the ground loop... From what I was reading and after talking with hvac guy he said that the close pond loops need approx 15 foot of water covering the top of the loop to work correctly and to avoid freezing issues.. My pond is 21 feet in the deep end but I had just built the pond and it was still filling up... He said it would work in the end but that the pond loops should be described as lake loops because of the actual water volume need to function and work properly..
The hvac guy said that if ground conditions were unfavorable ( rocky etc) the pond loop would b a good option, but in ideal conditions ground loop was preferable.
I went with the ground loop (horizontal) and the only difference was excavation cost which was minimal.... Stand up job the guys did, and heating/cooling savings have been substantial compared to similar sf homes with high effiency heat pumps.
Very happy with it and would highly recommend it.
The hvac guy said that if ground conditions were unfavorable ( rocky etc) the pond loop would b a good option, but in ideal conditions ground loop was preferable.
I went with the ground loop (horizontal) and the only difference was excavation cost which was minimal.... Stand up job the guys did, and heating/cooling savings have been substantial compared to similar sf homes with high effiency heat pumps.
Very happy with it and would highly recommend it.
whistlepig
Elite Member
Ours is horizontal ground loop also. We have had ours for 12 years now without any problems. I would also highly recommend it.
eepete
Platinum Member
When we installed our Geothermal in 2007, there were two 3 ton units that were exactly the same unit. We put one in a 1/2 acre pond with a maximum depth of about 9 feet, and the other we did a ground loop about 6' down in the ground.
Now the pond loop also had a 5 ton unit on it. Our geothermal guy said the pond loop would "work just fine". The systems were in use from August on. In January, I decided to take some measurements to see how the pond vs. ground were doing. Subjectively, it seemed like it was taking longer to heat the place up.
I've attached a .pdf of the measurements. One of the things to notice is that in January the pond water came in at 40 degrees, whereas the ground water came in at 56 degrees. Now I'll be the 1st to say that this is hardly an exhaustive or scientific test. It was hard to get the room temperatures the same, this is just one set of measurements, etc. The pond had the 3 ton and 5 ton units on it, the ground just had the 3 ton. As I did the test, the room temperatures went up which is why the delta is the number to watch. Yeah, it would be better if the room temp was exactly the same but... But, both the space heated with the 5 ton on the pond and the space heated with the 3 ton on the ground were brought up to 68 degrees each morning, so this is close. Also, the 3 ton unit on the pond was the Master Bed Room, and it stayed at 62 degrees all winter long so during the day it basically never ran. So the loads on the pond and the ground were "close".
The heat pumps are two speed compressor units. I took the temperature of the air in and out of the units, and you can see the delta temperature. Of course the temperatures from the pond and the ground didn't change at all during the tests.
What struck me here is that the ground loop did significantly better on just the 1st stage of the compressor, which is where things tend to run once a room is up to temperature. The 2nd stage of the compressor had the temperatures closer, but, the ground loop still won.
I showed this to my HVAC guy, he was surprised. Turns out he's never made these measurements, the "ponds are OK" was a very subjective "no one really complained about the system." As a result of this, he took the temperature of another pond system that had a 13 acre pond. The pond was at 42 degrees (vs. my pond at 40). So the size of the pond is not a big factor in the performance of the system (well, don't use a 1/10 acre pound either).
Based on this, I put the 3 and 5 ton that were on the pond onto a ground loop system. It throws the payback out to something insane like 12 years, but, well, Ok, that's just me
.
The cost for the pond loop was $8K. The cost for the ground loop was $13K. the cost difference is 90% the cost of digging up the ground. It is clear to me that If I had done the group loop up front, the extra cost would have come more than come back to me in the roughly 8 year payback period of the system.
I'm the only customer my HVAC guy has who has a back-up loop. I left the pond pipes and pumps intact, there are valves and switches to kick them in.
Enclosed also are pix of the pond loops before they were sunk, and the ground system before it was covered up. It takes about 18-24 months for those 6' deep trenches to settle out completely, so keep that in mind when doing any final landscaping.
Bottom line: If you can swing the cost, avoid the pond and go with the horizontal ground loops.
Sorry for long post, lots of data...
Pete
Now the pond loop also had a 5 ton unit on it. Our geothermal guy said the pond loop would "work just fine". The systems were in use from August on. In January, I decided to take some measurements to see how the pond vs. ground were doing. Subjectively, it seemed like it was taking longer to heat the place up.
I've attached a .pdf of the measurements. One of the things to notice is that in January the pond water came in at 40 degrees, whereas the ground water came in at 56 degrees. Now I'll be the 1st to say that this is hardly an exhaustive or scientific test. It was hard to get the room temperatures the same, this is just one set of measurements, etc. The pond had the 3 ton and 5 ton units on it, the ground just had the 3 ton. As I did the test, the room temperatures went up which is why the delta is the number to watch. Yeah, it would be better if the room temp was exactly the same but... But, both the space heated with the 5 ton on the pond and the space heated with the 3 ton on the ground were brought up to 68 degrees each morning, so this is close. Also, the 3 ton unit on the pond was the Master Bed Room, and it stayed at 62 degrees all winter long so during the day it basically never ran. So the loads on the pond and the ground were "close".
The heat pumps are two speed compressor units. I took the temperature of the air in and out of the units, and you can see the delta temperature. Of course the temperatures from the pond and the ground didn't change at all during the tests.
What struck me here is that the ground loop did significantly better on just the 1st stage of the compressor, which is where things tend to run once a room is up to temperature. The 2nd stage of the compressor had the temperatures closer, but, the ground loop still won.
I showed this to my HVAC guy, he was surprised. Turns out he's never made these measurements, the "ponds are OK" was a very subjective "no one really complained about the system." As a result of this, he took the temperature of another pond system that had a 13 acre pond. The pond was at 42 degrees (vs. my pond at 40). So the size of the pond is not a big factor in the performance of the system (well, don't use a 1/10 acre pound either).
Based on this, I put the 3 and 5 ton that were on the pond onto a ground loop system. It throws the payback out to something insane like 12 years, but, well, Ok, that's just me
.The cost for the pond loop was $8K. The cost for the ground loop was $13K. the cost difference is 90% the cost of digging up the ground. It is clear to me that If I had done the group loop up front, the extra cost would have come more than come back to me in the roughly 8 year payback period of the system.
I'm the only customer my HVAC guy has who has a back-up loop. I left the pond pipes and pumps intact, there are valves and switches to kick them in.
Enclosed also are pix of the pond loops before they were sunk, and the ground system before it was covered up. It takes about 18-24 months for those 6' deep trenches to settle out completely, so keep that in mind when doing any final landscaping.
Bottom line: If you can swing the cost, avoid the pond and go with the horizontal ground loops.
Sorry for long post, lots of data...
Pete
Attachments
thanks for all the opinions folks, I'm new to this{geo} but have been reading a lot. I was thinking a closed pond loop, from what I've read they're suppose to be more efficient then ground{??}. If that is the case my pond is less then 50' from the house. I am worried about freezing but our pond never freezes all the way to the bottom{even when we go 20 below 0} average might be 2' thick or so. Again thanks for the post keep them comming
patrick_g
Elite Member
When we went geothermal I could find few really good HVAC outfits that did geothermal and hydronics. None of the good ones would recommend a heat exchanger in a pond although a couple of my nearby ponds exceeded the requirements.
Here we are several years later and still super satisfied with our installation which includes 5 each 200 ft deep wells (no well water used, just big heat source/sink)
Pond loops are not maint free.
By the way, I'm in south central Oklahoma and our deep earth temp is 62.5 F. It is lots easier (and cheaper) to "mine" heat out of 62.5 degree source than ponds which freeze over in winter. I had assumed we'd go horizontal ground loop but was strongly advised that wells were better. Can't prove otherwise as I went with wells and have no data to compare for horizontal.
The ground sourced geothermal heat pump not only cools and heats much of the house it also preheats our hot water. It heats a 50 gal water heater (heating elements not connected) which is the input water for a 40 gal propane water heater. Doesn't use a lot of propane as the heat pump gets it up to 110 to nearly 115 F so the gas only has to heat it a little.
Pat
Here we are several years later and still super satisfied with our installation which includes 5 each 200 ft deep wells (no well water used, just big heat source/sink)
Pond loops are not maint free.
By the way, I'm in south central Oklahoma and our deep earth temp is 62.5 F. It is lots easier (and cheaper) to "mine" heat out of 62.5 degree source than ponds which freeze over in winter. I had assumed we'd go horizontal ground loop but was strongly advised that wells were better. Can't prove otherwise as I went with wells and have no data to compare for horizontal.
The ground sourced geothermal heat pump not only cools and heats much of the house it also preheats our hot water. It heats a 50 gal water heater (heating elements not connected) which is the input water for a 40 gal propane water heater. Doesn't use a lot of propane as the heat pump gets it up to 110 to nearly 115 F so the gas only has to heat it a little.
Pat
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whistlepig
Elite Member
No saying closed loop ground is better than open loop well or open loop pond but there are less uncontrolled variables with the closed loop ground system. Less things that can go wrong. Everything that I have read says open loop well and open loop pond is more efficient. Installation of open loop pond is considerably cheaper than a closed loop ground system. If I had it to do over again I think the closed loop ground system the best choice and well worth the extra cost up front.
JimRB
Veteran Member
We did 3 horizontal slinkys for our 3 ton unit. The HVAC guy's brother was our septic system guy so maybe we saved money. Anyway I guess it was cheaper than a deep horizontal system. No pond options. Closed loop has been maintenance free except for needing to add some dirt as the loop trenches settled over 13 years.
MWRR
Silver Member
- Joined
- Jan 9, 2011
- Messages
- 146
- Location
- East Central Illinois
- Tractor
- John Deere 5105M & IH Farmall 544
We built our house in 1994 and put in a closed loop horizontal 3 ton system with a 4 ton loop. We heat/cool 3286 Sq ft. We never open the windows. Our heating and cooling costs COMBINED are $300 a year. We also have the auxillary heating pump that preheats our hot water. VERY PLEASED with the system and never had a problem. It's a Water Furnace. Have never seen my auxillary heating kick in.
My sister put in an open system that runs off their water well two years ago. She heats/cools 5500 Sq ft. It seems to work ok. Whenever the system is calling for heat/cooling the water pump runs as well as any time they use water. Her system empties into their small pond (one acre or bit less). During the summer their pond gets VERY warm. I don't think I like here system as well as mine.
My sister put in an open system that runs off their water well two years ago. She heats/cools 5500 Sq ft. It seems to work ok. Whenever the system is calling for heat/cooling the water pump runs as well as any time they use water. Her system empties into their small pond (one acre or bit less). During the summer their pond gets VERY warm. I don't think I like here system as well as mine.
