Hello,

 I have asked questions before but was not prepared as well as I should have been, I now have the Manual J (heat loss calc). 64000 btu/5 ton.

I met with the geo contractor last week, he came up with 2 bids, 4 ton and 6 ton, I don't understand why.
A 200 ft horizontal bore closed loop per ton, ~20ft depth.
Waterfurnace 2 stage.
$20000 for the 4 ton.
$26000 for the 6 ton.
No aux heat (wood backup), desuperheater included.
I do all the duct work, new house, SIP/ICF, but 3 large vaults and large windows which don't help as far as energy efficiency.

I have come up with a list of adavatages/disadvantages for open/closed loop, there are sure to be other factors I have not considered.

Open loop - 3/4 hp pump, can only do this if it passes the water tests (Hydron/Enertech page 27 specs).
So if the water passes.......
Open loop is cheaper, more maintenance (need unions at heat exchanger and external pump to clean HX with muriatic acid periodically), need valves at water outflow, water can be used for household purposes, better efficiency at end of heating season, risk of water output freezing (solvable), possibly higher electricity cost due to pumping more water then a closed loop,

Closed loop - higher cost ($1600 per ton), lower maintenance, cheaper heat exchanger (don't need cupro-nickle).

Comments?

 thanks Steve

I would use a two pump design - a smaller well pump that provides low pressure for geo and then a booster for household water. Using 50 psi water for open loop geo is inefficient. I'd use valves instead of unions to make heat exchanger cleaning easy.

Closed loops may have higher initial costs. Over the life of the system , there will be far less problems which will calc out to reduced maintenance cost .

Unless special circumstances call for it,we are trying to discourage open systems. Closed systems are just so predictable, and much better to control. No Ni.Co coil, no running dry well in the middle of the winter, lesser risk of pump (circulation versus Well pump) failure with easy inside access if it occurs. The open systems had to have at least 5 figure price advantages for us to consider them.

All good points.
I am leaning towards the closed loop, the installer was concerned about rocks, my one and only neighbor had a rock the size of a small room where his septic system was supposed to go (they managed to move it), most large ones we dug up for the house were a few feet across. The contractor says they can backup the bit a few feet and point it in a different direction to get around the rock.

Also many large trees where the proposed bore comes up through the ground.

thanks

Steve

I agree that the closed loop has all good points, but don't discredit open loop entirely.  I live in NH and debated about open or closed loop.  I ended up with open loop, and am VERY glad I did.

On the well pump, we went with a vari speed pump.  The well is 354' deep and the pump is set @ 330'.  There is less elec load at start up and has a longer performing life. Although they do cost more than a standard pump.   I have a program that monitors all my electric circuts.  This winter, Nov 1 thru Apr 30th my well pump cost was $162 ( 1,252 KW ).  That also includes all the water for the  house.

The Geothermal operational cost for that same time frame was 2,963 KW ( $385 ).  I took a lot of readings and my entire winter avaerage for COP was 4.4.
We kept the house at a constant 72 never turning it down.  (My well temp never went below 51 degrees)

Now that summer is coming, my effeciency is only going to get better.  The well pump costs are no where near what I thought they would be.   My entire year of heating & cooling costs will be about $750 give or take a little.

As for maintenance,  I cleaned the inline water filter twice this winter, and just checked the coils which need no cleaning.  I will replace the air filter this weekend.

I couldn't be happier with our system ( Hydron 3 ton).  I know not all systems have this performance, but the cost difference between open & closed loop allowed us to build the attached garage which we planned on doing 1-2 yers after the house was built.

Good luck with your decision.

Mike

Posted By nhgeo1 on 26 May 2011 09:07 AM
Steve

I agree that the closed loop has all good points, but don't discredit open loop entirely.  I live in NH and debated about open or closed loop.  I ended up with open loop, and am VERY glad I did.

On the well pump, we went with a vari speed pump.  The well is 354' deep and the pump is set @ 330'.  There is less elec load at start up and has a longer performing life. Although they do cost more than a standard pump.   I have a program that monitors all my electric circuts.  This winter, Nov 1 thru Apr 30th my well pump cost was $162 ( 1,252 KW ).  That also includes all the water for the  house.

The Geothermal operational cost for that same time frame was 2,963 KW ( $385 ).  I took a lot of readings and my entire winter avaerage for COP was 4.4.
We kept the house at a constant 72 never turning it down.  (My well temp never went below 51 degrees)

Now that summer is coming, my effeciency is only going to get better.  The well pump costs are no where near what I thought they would be.   My entire year of heating & cooling costs will be about $750 give or take a little.

As for maintenance,  I cleaned the inline water filter twice this winter, and just checked the coils which need no cleaning.  I will replace the air filter this weekend.

I couldn't be happier with our system ( Hydron 3 ton).  I know not all systems have this performance, but the cost difference between open & closed loop allowed us to build the attached garage which we planned on doing 1-2 yers after the house was built.

Good luck with your decision.

Mike

I am glad you had a good experience. Yes, variable speed technology is great to have. You just did not have (yet!) plugged up heat exchangers, failed well pumps in the middle of winter, frozen discharge lines or plugged discharge wells....

I am about to go online with my new open loop system. Since I have an overflowing well I am not worried about freezing discharge or a discharge well. I expect to be able to maintain the heat exchanger but my water is not that bad anyway. So my only real concern is the failed well pump in the winter but it is a new variable speed pump so I don't expect that to happen. If/when it does its probably only a once (maybe twice) in a lifetime experience and the well is accessible and I have adequate backup heat. I figure that if for some reason I'm not happy with the open loop or something drastic happens to my aquifer then I'll put in the ground loops. I'll be out a little money for the extra cost of the cupro nickel heat exchanger and some plumbing. The variable speed pump I want for my house anyway. I certainly understand the installers preference for closed loop but as a consumer I think the open loop should be considered. You just have to know what the considerations are. I would not have been able to afford a closed loop system regardless of the payback.

Based on readings here, for homeowners that switch loop configurations it is much more common for them to switch from open to closed loop as opposed to closed to open loop. Closed loops remove some of the variables (water quality, water supply, iron bacteria, etc.) that could adversely effect an open loop system. However, as has been pointed out previously, open loops can work well.

Another thing to consider is that the tax credit can be used to help offset the higher cost of a closed loop system. I'm not sure if the tax credit would be available for a future closed loop conversion if an open loop is chosen now.

Is your installer confident that he can overcome your geology when installing a horizontal loop system? Have you investigated vertical closed loop pricing to see if that option is possible?