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Corrosion of copper in DX geothermal?

Posted by jmfrater (My Page) on
Thu, Feb 14, 08 at 12:16

We are building a house in a town about 2 hours south of Chicago. We've received two bids for a geothermal heating/cooling system, both using regular or water-sourced systems. After reading posts on this forum, I called one of the contractors to inquire about using a direct exchange (DX) system instead. He said they haven't put them in for more the 10 years because they found the copper tubing corroded in the ground and had to be dug up and reinstalled. Has anyone ever heard of this happening? This company had 30 years of experience with installing geothermal, so I'm inclined to go with their recommendation. Thanks for your feedback.


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RE: Corrosion of copper in DX geothermal?

Re: jmfrater

Yes I have heard about this problem but not in your part of the country! What you need to know is the acidity of the soil in your area. If its ph is neutral, youre OK; its as simple as that. Do they use copper lines for the water mains into homes in your area? How often do those have to be replaced, every forty, fifty, or sixty years?

Years ago, for a multitude of reasons, there were problems with DX installations. That is NOT the case today. Most people who install regular geothermal wont touch DX, perhaps more out of ignorance than anything else. Many of the installers who cross over and do DX stop doing regular geothermal because if the ground is ph neutral, these systems are much easier to design and install not to mention much less expensive.

One installer you spoke with said that the copper tubing corroded. If the soil were close to neutral, I would suspect that the copper ground loops were improperly fabricated and/or installed, not corroded by the ground. Unless he dug them up it would be hard to know. Certainly vertical ground loops would be difficult to extract. Its much easier to say they corroded, therefore they leaked. That way the installer exonerates himself, if you can excuse not knowing the soil ph.

Im an IGSHPA accredited installer who can install either system. I personally have a DX system in our own home. I have nothing but praise for it. Were in our 5th heating season and have never had to have it service, repaired, topped-off, oiled, lubricated or anything like that. Ive replaced 1 fan belt and other than air filter replacements thats been it.

Let me explain it from my perspective. I see it this way with this analogy; its like the war between PC computers and Apple computers with PC being regular geothermal and DX being Apple computers. A clash between formats. Much like Beta vs. VHS.

Installations other than residential and small commercial should definitely be HDPE water loops, no question about that. If youre going to fret about your ground loops being copper and loose sleep over it, go with HDPE water loops.

Speak to installers who do DX, ask for references and contact them. See if you can visit some of these installations. Call the manufacturer of any DX HP youre considering and see what kind of answers and support you get from them. Go with the installer you feel will do the best installation. If they only do water to air and not DX, go with them anyway. Your water to air HP contractor should be IGSHPA accredited. As with anything do your homework!

Testing the ph of your ground water may give you an indication of what your soil is like (for DX installations). Speak to a local well driller or geologist, that would be your best bet.

BTW: This post was written on a Mac I would NEVER use a PC by choice!

IMO

SR


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RE: Corrosion of copper in DX geothermal?

What about a coastal environment? Would brackish water preclude installing a DX system?

Thanks


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RE: Corrosion of copper in DX geothermal?

Have your soil and ground water analyzed. Copper ground loops in slightly acid soils can be protected by the installation of a sacrificial zinc anode.

If you cannot be given the assurance that copper is safe, install a plastic HDPE liquid ground heat exchanger and appropriate heat pump.

Perhaps an indication of soil conditions would be whether copper pipes are used for the domestic water lines into houses in your area and how long a life span they have. Have your contractor provide you with references you can verify that have had a DX system without any trouble for at least 5~10 years minimum. If its brine youre concerned about speak with a chemist.

SR


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RE: Corrosion of copper in DX geothermal?

Personally I think DX overstate their efficiency claims. I've just completed a bidding process and chose closed loop over them. The tonnage for the DX was twice that of the closed loop(and twice the cost) for the same manual j calc. Unless you have money to waste I would just go with proven closed loop furnaces like climatemaster etc. I'll be installing a climatemaster tranquility series.


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