Solar & Radiant floors

Wayco Wayne

I helped my friend Hugh put radiant tubing and insulation in a garage floor he was pouring in an out building on his farm. He wants to build a solar panel or 2 and have the slab storing heat during the day while the sun shines. That should be easy enough, but when it's night or cloudy how could one integrate some backup heat into the loop?

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David Woycio

solar tie in

Wayco,
We have been insrtalling these types of systems since 1982 in Colorado and usually use a heat exchanger tied to a boiler. Be careful in your plumbing so as to protect your tubing from overtemping. Stagnation temperatures from solar collectors can reach over 250 deg F. Also make sure to install an anti-thermosyphoning device (spring check works) so as not to cool your slab in the evening. In the summer these panels will be baking, so either cover them or use the heat for domestic hot water or a pool. By the way, we have a large sellection of used and rebuilt solar collectors in stock. Give me an idea in BTU's what your load is and I'll size the collector area for you.

Paul Pollets

Consider

that when we're in heating season, the solar cycle is at it's lowest ebb. Depending upon the location, it's possible to do with a buffer tank, but may not be cost effective. Many use a woodstove (or wood boiler) with a water jacket to supplement the heat. Some good solar info available at www.thermomax.com

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Mark Eatherton1

Simple solar and RFH

Wayne, I had a student at one of my RPA courses that invited me to his house to see his system. He had a 2-1/2 car garage that was super insulated (R19 walls, R4- ceiling) and had collectors mounted in a lean to configuratuion along the south side. The slab was insulated with 2" foam, and the concrete was 12" thick in the middle, and 4 inches thick on the edges. The system was a simple drain back system with a 3 way diverter valve. When the sun was out and the collectors hot a pump turned on delivering the heat to the slab. Once the slab was satisfied, if there was still solar available, he sent it to a slab on the outside, north side of the garage via a 3 way diverting valve.

This gentleman raised earth worms as a hobby in his garage.

There was NO back up in the garage.

He said that in the 4 years of operation that he had NEVER had to shovel snow off the north facing slab, and he had never lost any earth worms (they die below 45 degrees F).

Maybe you don't need back up heat.

ME

Hugh Stamper

I'm the \"Hugh\" in Wayco Wayne's query

and I'm excited to have found The Wall through him. I'm basically just playing with this system. I have been interested in solar for a long time and, since I was putting a concrete floor in my 125 year old garage, I thought I'd just stick some pex tubing in and see if I could keep my feet warm as I work in my shop that will soon be fully functional. As hoakie as it will seem to you more sophisticated folks, I'm planning on starting by plumbing in an old cast radiator or two--painted black--as the solar collectors. Does this seem like a totally stupid idea? I'm basically a cheapskate experimentalist and I'm just in this for the fun and the challenge.

Paul Cooke

Solar

Hugh

As long as you are tinkering around, you might as well search and find some used glazed solar panels. There should be some around, and they will give you the kind of water temps you would need for your garage. You won't get much above ambient air temps with the radiators.

What part of the country do you live in? Do you have many sunny days in the winter months?

David Woycio

solar 101

Hugh, Think in terms of surface area when considering solar energy collection. If you have any radiant trak around paint it black and use it as your absorber plate. Use your pex as the collector tubing (underside of plate away from sun) and angle around 55 deg. You are now in reverse radiant mode. Of couse if you insulate, fab in a box, and put glazing over the whole thing you will have built a flat plate solar collector. Watch those temps!

Paul Cooke

Solar

PEX would not likely handle the temps that a glazed solar panel can reach. Stay with copper.

Paul Cooke

Solar

PEX would not likely handle the temps that a glazed solar panel can reach. Stay with copper.

Hugh Stamper

tinkering and used solar panels

Thanks for the comments guys. I live in Maryland just north of DC and we do get lots of insolation. I don't know the statistics, but I'd say it's definitely more than 50 percent of daylight is sunny, possibly even up to 75 or 80 percent. I got a response from one person here (in Denver) about used collectors, and I'll be following up on that as soon as I get to that point. I guess I won't bother with the radiator since it sounds too minimal in size, and I don't have any of the pex any more, since I sent back the unused part to Wayco Wayne. Thanks for your help on this to all responders.
...Hugh

Wayco Wayne_2

What do you do wih

the solar panels in the Summer when there's no place to send the heat? Do you drain them down?

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Unknown

HHhmmmmmm

Absorbtion air conditioning....

Pool and spa heating...

Domestic water heating....

Insulated thermal storage (only on a huge scale, to be used with the other loads)...

Noel