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

Thu Jan 11 19:44:24 CST 2007

Reading between the lines, several of the comments here have been about 
open-loop systems. We should always make this distinction explicitly 
when talking about geothermal, since it's an entirely different 
arrangement. The closed loop is generally more expensive to install and 
a little less efficient to operate, but the most responsible way to do 
it IMHO, and perhaps the only legal way in some places. It would be 
helpful for people to make this distinction as they wrote about specific 
geothermal systems.

Keith

Lawrence Lile wrote:
> 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
>>
>>
>> _______________________________________________
>> Greenbuilding email list
>> List info:
>>     
> http://listserv.repp.org/mailman/listinfo/greenbuilding_listserv.repp.or
> g
>   
>> List email: Greenbuilding at listserv.repp.org
>> Managed by BuildingGreen, Inc. http://www.buildinggreen.com
>>       publisher of Environmental Building News and GreenSpec(r)
>> Hosted and archived by REPP / CREST http://www.crest.org
>>
>>
>>
>>   
>>     
>
>   

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