Tempering HRV intake air w/ ground loop

Tempering HRV intake air w/ ground loop

Postby jessethompson on Fri May 15, 2009 10:25 am

I have heard several people in this community talking about using a simple ground loop buried below frostline to circulate water in the incoming airstream of an HRV or ERV and temper the incoming air stream in summer and winter.

I am about to start someone running numbers to see if this system makes sense for a house we are designing, but wanted to ask if anyone here has any pointers or experience that would be valuable before we go too far. Any pitfalls to watch out for?

Working assumption has to be that the expense and complexity of adding this system is worth more than the loss in efficiency of a modern HRV / ERV running at those extremes.

Air handlers / coils to recommend? Control issues? Effectiveness at our temperature extremes? (-5 F winter design day, 100 F / 90% H New England summer).

Thanks in advance,
Jesse Thompson, AIA, LEED AP
Kaplan Thompson Architects
http://www.kaplanthompson.com
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Re: Tempering HRV intake air w/ ground loop

Postby Roger Woodbury on Fri May 15, 2009 3:14 pm

Jesse: Have you looked at http://www.comfosystems.com?

These are products from Zehnder. I have spoken with the factory rep and the systems sound terrific for Passive House or other highly restrictive performance standards.

I do not know the actual specs yet, though.

Roger
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Re: Tempering HRV intake air w/ ground loop

Postby jessethompson on Mon May 18, 2009 7:41 am

I saw the Zehnder systems when Barry Stephens showed them at the Brandeis gathering, but they're not commonly available in the US yet. I've heard of people custom designing similar systems in the past and hoped to learn from their experience.

Another good link on similar systems, the Germans call them Brine Ground Heat Exchangers: http://www.sole-ewt.de/index-e.html
Jesse Thompson, AIA, LEED AP
Kaplan Thompson Architects
http://www.kaplanthompson.com
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Re: Tempering HRV intake air w/ ground loop

Postby Mary Graham on Tue May 19, 2009 4:32 pm

Condensation is the issue with directly tempering the air. Make sure you have a mechanism to deal with humid summer air condensing in the cool tempering tubes.

It sounds like you're talking about indirect tempering with hydronic loops. The up side of that is that it should prevent freezing in an ERV core in the winter. You'll need to invest in some preheating system to prevent winter freezing.
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Re: Tempering HRV intake air w/ ground loop

Postby jmorosko on Tue Oct 06, 2009 8:44 am

Just as a note... we now have a 12" water to air coil, packaged, insulated,... for use as ground loop coil, pre heat, post heat... and what not. 160 F water temp, 2.5 GPM, 200 cfm air... 8700 btu/hr... please contact ultimateair.com.. thanks
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Re: Tempering HRV intake air w/ ground loop

Postby markuskolb on Tue Nov 10, 2009 1:21 am

If I'm not mistaken, that's exactly what Kat did at the Stanton house, and I think I remember hearing that the plan was to update the system with Jason's new heat exchanger (see above post). I believe the PEX is buried below the slab at the Stanton house, and yes, I do remember seeing a condensate drain as well (Mary, I think this heat exchanger would be the pre-heater to avoid HRV/ERV freeze-up).

Cheers,
Markus
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Re: Tempering HRV intake air w/ ground loop

Postby timeian on Wed Nov 25, 2009 11:04 pm

We are about to break ground on a project with 600 lineal feet of 1" pex, connected to a liquid to air heat exchanger from Luefta from Germany. The system is calculated to deliver about 1.5kW of peak energy and eliminate pre-heating of the intake air. This is for a building in Western Wisconsin (near the TwinCities) in climate zone 6. The loops are buried at a minimum of 6 feet below grade, at a distance of min. 20" from each other. The calculated shx efficiency is at 60% according to the German engineering we had done.
--
Tim Delhey Eian
Dipl.-Ing., Assoc. AIA, PBD AIBD,
Certified Passive House™ Consultant
TE Studio, Ltd.
3429 Benjamin St. NE
Minneapolis, MN 55418
612-246-4670 office
612-605-3200 fax
http://www.testudio.com/
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Re: Tempering HRV intake air w/ ground loop

Postby Dave Brach on Wed Dec 02, 2009 9:54 am

If the ground loop is buried under the slab, would one need to account for the higher heat losses through the slab or is it negligible?
Dave Brach AIA
Salt Lake City, Utah
Brach Design Architecture
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Re: Tempering HRV intake air w/ ground loop

Postby Roger Woodbury on Fri Dec 04, 2009 8:16 am

Do you have an actual electrical consumption figure for this system? Will this system provide all of the heat needed for the project of will there be an additional heating system of some sort? What is the source of electricity for this house?
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Re: Tempering HRV intake air w/ ground loop

Postby robharrisonAIA on Mon Jan 31, 2011 1:58 pm

Any updates on the products for this technique in the last year? We're working on a project on a site with ~7,900 HDD, and some sort of ground tempering is going to be necessary. An earth tube doesn't seem prudent in this area of high radon....

Thanks.

Rob
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HARRISON architects
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Seattle, WA USA

lyrical sustainable design
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