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loop size

Last Post 04 Nov 2009 04:05 PM by dkubarek. 8 Replies.

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homeowner1111 User is Offline

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Posts:1

01 Nov 2009 09:34 PM
I am having trouble with my electric bills ever since installing my geo system two years ago. I have done a lot of research and it seems to possibly point to an undersized loop. My loops are five hundred and fifty foot horizontal 3/4 inch and there are three placed six feet deep and approximately 1.5 feet apart. So in all I have over 1,600 ft of 3/4 inch pipe buried. The escavaters bucket was five feet wide and they layed all three pipes at the bottom of the trench. I live in a cold weather climate with a heating load of 48,000btu/hr. My deep earth temp here is 49 degrees freom the research I have done. Is the problem here my loop?? I don't know how to calculate everything out to find out if it is. Oh yes and my water temps are routinely over a hundred in the summer and in the twenties in the winter. Thankss

Palace Geothermal User is Offline

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Posts:1609

01 Nov 2009 10:56 PM
You loop temps indicate that you have an undersized loop.

Dewayne Dean <br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system

joe.ami

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02 Nov 2009 06:40 AM
Could also be air in the loops or lousy compaction. Who designed this system? What size heat pump do you have? joe

Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!

Alex_in_FL User is Offline

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Posts:96

02 Nov 2009 03:58 PM
Just typing my thoughts: Three 550 feet slinky loops buried 6 feet deep seems reasonable for a 3 ton unit, maybe 3.5 ton unit if properly installed and you accept some use of auxillary heat. What concerns me is that the trenches are only 1.5 feet apart. This means the middle trench has only vertical heat sinks and the other two only have three sided heat sinks. So, my guess is that the loop is insufficient due to crowding the loops too close together.

dkubarek

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Posts:85

03 Nov 2009 05:44 PM
loop location sounds suspect to me too. Installers have suggested 15 feet apart at our place. Probably done to save money. That sucks for the poster because that requires a reinstall. Maybe you can fight it out with the installer and get it in for less.

Down2Earth Geothermal User is Offline

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Posts:59

03 Nov 2009 09:10 PM
This sounds like a standard 3-pipe system install in a single 550' long and 4-5' wide trench where the pipes are laid in the bottom spaced equally apart. About 2' of backfill is added and the loops are routed back in the same trench in a similar fashion. If this is correct, and you have good soil (moist or wet silt/clay) this should be fine for your heat load and you are not short-looped. However, your loop temps do indicate a loop problem. I would do as suggested above in 1) check to make sure the soil is compacted around the loops by flooding the trenches with water and see if you have subsidence indicating voids and 2) get a geo contractor to purge the loops to remove any trapped air by achieving 2 fps velocity for 15 min. -Adam

joe.ami

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04 Nov 2009 07:09 AM
Posted By Alex_in_FL on 11/02/2009 3:58 PM Just typing my thoughts: What concerns me is that the trenches are only 1.5 feet apart. This means the middle trench has only vertical heat sinks and the other two only have three sided heat sinks. So, my guess is that the loop is insufficient due to crowding the loops too close together. If not familiar, 2, 4 and 6 pipe trenches all have pipes fairly close together but trenches farther apart. not sure if OP is describing a 6 pipe as Tek mentioned with back 2' of back-fill and return pass or a true 3 pipe which would out perform a 6 pipe trench by returning via another route. j

Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!

joe.ami

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04 Nov 2009 07:16 AM
By the way, still waiting on the size of the heat pump....we're all blowin' smoke without that.... paging OPoster. j

Joe Hardin www.amicontracting.com We Dig Comfort! www.doityourselfgeothermal.com Dig Your Own Comfort!