Geothermal Loops?

[Rayrla]

Our 5 ton geothermal system with a 4000 foot horizontal ground loop system was installed this summer. 1 1/4 inch main in and out pipes (approximately 125 feet) were buried in a trench which started at a depth of 3 feet at the house and ran out to a depth of 6 feet. At the end of this trench, a manifold was placed and two 400 foot six foot deep trenches were dug with an excavator with a 4 foot bucket. One trench was eight feet wide and the other was four feet. In the eight foot trench, three 3/4 inch loops were placed, and in the four foot trench, two 3/4 inch loops were placed. Installation of ground loop took less than a day and a half. Works great so far!

 

[20 20]

It was built in 1860 with remodel in 1990's but they didn't use any insulation.


This is where I'd definately put some reassurance, insulation, IMO, can make or break a house for heating and/or cooling. A person can have the biggest badest setup there is but without good insulation it won't mount to a hill of beans

 

[LD1]

The slinkeys are becomming more and more popular. But you are right, they arent quite as efficient and require a little more pipe.

Last time I researched things, the reccomendations were 600-1000ft per ton. Closer to 600 with straight pipe, closer to the 1000' mark for slinkey.

BUT, usually the extra added excavation cost more than the extra line to run the slinkey.

And they also reccomended 4-5' depths for a horizontal slinkey. IE: dug with a 24" backhoe bucket and slinkey coils laid flat in approx. 2' coils. The other option was with a 6' trencher and stuff the slinkeys in vertical. Also with 2' coils. This would put the top of the slinkey @ the 4' depth.

So...5' may be pushing your luck. I'd probabally go ahead and rent the 6' machine for a day and do vertical slinkies.

And I think the reccomendation was like a 6:1 ratio. So 600' of line, slinkey fashion, in a 100' trench. vs the 2:1 like your horizontal straight runs.

 

[lilranch2001]

I am no expert by any means but I was told by an "expert" that open loops do not last as long and is more maintenance problems due to the hard water minerals

 

[LD1]

I am no expert by any means but I was told by an "expert" that open loops do not last as long and is more maintenance problems due to the hard water minerals

That is what I have heard too.

IMO, if conditions permit, the best (cheapest and most efficent) method I have seen is a closed pond loop. Where the lines are sunk into the bottom of a sizable pond. Water transfers the heat better than soil, and it is less excavating IF you already have a pond. Just trench a line out to the pond and you are done excavating.

 

[whistlepig]

There has been a lot of discussion on this forum on open loop verses closed loop. Open loop is more efficient than closed loop. We have a Waterfurnace closed loop. The Waterfurnace tech that services our geothermal says most of his calls are do to hard water deposits on the open loop systems. Others say they have used open loop systems for many years with no hard water deposit problems. Another consideration on geothermal is that the geothermal compressor doesn't last forever. I have heard 25-30 years is the life span of the compressor and replacement cost is roughly $8,000.00.

 

[JimRB]

I had to put a calcite filter in my house water because the low ph was eating up my copper pipes. I supose it is not just hardness but ph to consider in an open loop. My installer brought his own water to put in the slinkies.

 

[buckeyefarmer]

Geothermals are great systems, just a little costly.
A slinky doesn't require much more pipe than a straight run, but it's a lot less digging. If you search, I've provided the differences in lengths in other posts for my design.

Also, most installers are going with closed loops. There are more issues with open loop systems. Number one you have to be sitting on top of a good aquifer, and number two, you can't dump the water straight back into the aquifer. Number three is the pump for open loop is a lot larger than a circulating pump, so more electric used. Also the life of the heat exchanger will be less, depending upon the quality of the water you are pumping thru it. The HDPE pipe is one of the cheapest parts of the system, the labor is the largest part.

 

[whistlepig]

Not to sell geothermal short. If you buy a furnace and it is rated at 99.9% efficient a point to remember is that geothermal is rated at 300% efficient. Geothermal is a very good thing to consider.

 

[sawduster98]

Not to sell geothermal short. If you buy a furnace and it is rated at 99.9% efficient a point to remember is that geothermal is rated at 300% efficient. Geothermal is a very good thing to consider.

Not to mention A/C is included if you run forced air and the cooling efficiency of geo is higher than heating.
I run a Climatemaster 2 ton unit for my 1800 sqft house. It was a new build and we had the place insulated very well. After looking at new gas furnaces + A/C units I decided to spent the extra $5k on geo. Found a lot of dealers jacking up prices as some estimates were as high as $40k. Mine cost $14k and I couldn't be happier. After a full heating/cooling season our electric bill was low enough I decided installing solar power would no longer be cost effective.