I have been reading the posts about geothermal and all seem to refer to open-loop systems. I live in South Florida next to the ocean - it's as awesome as it sounds - so I don't have access to clean water wells. It seems that my only option is a closed-loop system, but I am not sure if this is the case. If it is, does this makes the project too costly, significantly less efficient or complicated?

Posted By Martjmart on 13 Apr 2015 05:37 PM
...does this makes the project too costly, significantly less efficient or complicated?

Too costly? .... Depends on local drilling prices. Get a few quotes.

Less efficient? .... No, not with a properly-sized & installed closed loop.

Too complicated? .... No, less complicated, IMO -- and most reliable.
No worries about water quality or quantity, no submersible pumps, etc.

A frequent poster on here, Curt Kinder, is up near the Jacksonville ST. Augustine area and it seems he has done open-loop systems frequently. The artesian well flows and water quality are fairly favorable in that area for open loop. Depending on hydrology in your region, open-loop may be viable. In a tropical rainy climate as you are, open loop may make sense, as you can expect the well won't run dry. Open loop is much more a gamble in areas with variable wells and periods of drought.

so I don't have access to clean water wells. It seems that my only option is a closed-loop system

.....So is everyone there on municipal water of some kind?.........

.....my only option is a closed-loop system....does this makes the project too costly

If one had to drill a supply and a return well for open loop, depending on many things, that could cost more or less than a closed loop system. Factors are size of dwelling/heat loss/gain, size of lot (can we use horizontal loops or must they be vertical), depth of aquifer, quality of water......

significantly less efficient

Less efficient. Absolutely. This due to higher winter water temps and lower summer water temps.
That said, pumping well water has a cost of it's own that is often not calculated in efficiency models so actual operating cost may be similar between loop systems.

complicated

Hmmmm, I'm having trouble with the word complicated. I think in some ways (particularly for the designer) open loop is less complicated. Most saavy contractors exclude themselves of responsibility for water quality and quantity so you can't screw up the loop field. Meanwhile in closed loop if you have a drought and the pond level goes down or the soil drys out on a horizontal loop system no one wants to hear it's not the designers fault when the system doesn't perform.

Flip side is with closed loop you only have a circulator or two and as long as designed right and asssembled correctly little else can break. with pressurized systems you may have to pump pressure up a little after a year or so.

Open loop on the other hand may have a prefilter that requires maintenance, it will also have a solenoid that may fail, a flowrater that could foul or for that matter the drain or heat exchanger could foul in areas of high iron content in the water. Drains can plug with any number of things including ice in the winter in more northern climates. Then lest we forget leaks are possible and water damage and most expensive of all is the well pump could fail due to the excersize of pumping an extra million or so gallons of water each year.

I will say that I think the "added maintenence of open loop" card is overplayed but it is not completely false. In spite of that, open loop is attractive to folks with large loopfield requirements (much lower first cost) or folks with artesian wells where flow doesn't require pumping. I've also had folks who took advantage of water they were already pumping to fill a pond that wasn't self sustaining and of course open loop is attractive to do-it-yourselfers as more people understand basic plumbing vs fusion of HDPE and flush carts and fusion tools are much more expensive than a PVC cutter and solvent.

I'm suspicious that open loop is the most common of geo systems in the US as they have been installed for ~65 years now with closed loop gaining popularity in the last ~30. The tax credit closes the gap between first cost of open loop vs closed loop systems and I think that has impacted closed loop popularity in areas where open loop systems are common.

Your heat pump will not care what kind of loop system you buy, It only cares that it is sized correctly and that it gets the necessary GPMs.

Good Luck,
j