[Greenbuilding] Ground-source heat pumps

[Keith Winston]

This reinforces my comments of a moment ago: I think there are lots of 
good reasons not to install open-loop geothermal systems, wear on your 
system being only one (another is, I don't like pumping up water and 
discharging it as surface water. It bugs me, just in principle. Few 
people injection-pump it back down...). I would expect heat exchanger 
failure, since you have no idea what minerals are in that water, so the 
chance for deposits destroying your heat exchanger seems very good...

Keith


Rob Tom wrote:
> On Thu, 11 Jan 2007 11:36:23 -0500, Leslie Moyer <Unschooler at atlasok.com>  
> wrote:
>
>   
>> Steve Tripp wrote:
>>     
>>> One thing I have noticed after talking to several General Contractors  
>>> about geothermal systems is that there is not a lot of good information  
>>> out there about reliability and performance.  10 years seems to be  
>>> average that they give these systems to last before requiring major  
>>> repairs.
>>>       
>> This just doesn't seem accurate to me--it goes against everything I've
>> heard about them. I'm not connected to the industry at all
>>     
>
>
> I'm not connected to the HVAC industry either but I can attest to the  
> accuracy of Steve's assessment.
>
> When I built my home about 20 years ago, I considered installing a GSHP.
>
> Ultimately I decided that the $10-$20k initial cost (which included the  
> cost of drilling a second well through bedrock for the discharge) for an  
> auxiliary heating system that wouldn't see much use wasn't a very prudent  
> investment.
>
> One of my neighbours who built a couple of years after me did install a  
> GSHP, the brand touted as being *the* most advanced and best in North  
> America. The heat exchanger failed less than three years after the unit  
> was installed. I think the repair cost was ~$2-3k IIRC. (Gimmee a break.  
> It was almost 2 decades ago eh ?) Apparently there was some galvanic  
> incompatibility with some of the components resulting in premature  
> corrosion. We'll assume that problem has since been resolved.
>
> Not long after I heard about that failure, I encountered a fellow on the  
> other side of town (where they actually has a soil overburden) who had  
> ripped out his GSHP in disgust and was offering it free to anyone who  
> wanted it. The heat exchangers had failed three times at intervals not  
> exceeding three years, at $#### each pop. The third failure was the straw  
> that broke the camel's back for him.
>
> I then started looking around for similar experiences and theirs was not  
> unusual.
>
> One failure might be a freak incident. Two heat exchanger failures might  
> be a coincidence. Three or more has the indications of a pattern.
>
> The most common explanation for the HX failures (according to the  
> installation/repair contractors) is that the hard water in this area is to  
> blame. I never got a more in-depth explanation as to why the hard water  
> would be the culprit. Interestingly, an engineer in this area who was  
> connected to the industry denied ever having heard of such failures. I  
> introduced him to the GHSP owners that I had encountered and I'll bet his  
> hearing improved.
>
> In retrospect, my decision to install a big toaster (ie electric furnace @  
> less than $400) as the Code-required, automatic auxiliary heating system  
> seems to have been a good one. Never mind the fact that it has never been  
> fired up in the over 20 years that it has been "in service".
>
> To be fair, GSHP technolgy and design has undergone changes in the 20  
> years since I first looked at them and no doubt, a lot of the bugs have  
> probably (hopefully) been resolved satisfactorily.
>
>
> === * ===
> Rob Tom
> Kanata, Ontario, Canada
> <A r c h i L o g i c   at  c h a f f y a h o o   dot   c a >
> winnow the chaff from my edress in your reply
>
>
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>   

-- 
Keith Winston
Earth Sun Energy Systems
Hyattsville, MD 20781
301-980-6325
send me mail at 
keith at the company below
www.EarthSunEnergy.com