[Greenbuilding] [BULK] Re: Ground-source heat pumps

Thu Jan 11 17:11:22 CST 2007

The units we spec around here are closed loop systems - a loop pumps
down the well and then back up, never sees any direct groundwater.  The
authorities are not pleased about people pumping things into the
groundwater, or pumping it out either.  Too many residential wells.  

Yes, if a geothermal system goes kaflooey, you are in for a really
expensive repair bill.  I've heard of some premature failures myself.
That risk is another reason I shy away from them.  Insulate, insulate,
add South glass and laugh at the cold.  

Lawrence Lile, P.E., LEED AP

-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Keith
Winston
Sent: Thursday, January 11, 2007 5:04 PM
To: Greenbuilder list
Subject: [BULK] Re: [Greenbuilding] Ground-source heat pumps
Importance: Low

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

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