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  #1  
Old 09/27/06, 07:55 PM
 
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Arrow Home made radiant heat system.

I am building a cabin and I want to make my own radiant heating system. I am gonna build an out side wood burner and run black pipe through it back and forth several times to heat up water that will circulate through the concrete slab floor of the cabin. This will also be my hot water heating system. I am a pretty good welder and have extensive experience in pipe fitting. I already have a circulating pump and controls with theremostat.

Has anyone out there built a similar system and if so any tips will be appreciated.

Johnny

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  #2  
Old 09/27/06, 08:24 PM
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My PEX tubing is in place, but not hooked up to the boiler yet.

3/4" PEX, ran along the frame-bays with 18" wide aluminum flashing mounted as radiant-fin stapled up onto the subflooring.

I have a thermal-bank going too. And in talking to local contractors, they recommend it.

I have six oil-drums [55 gallon] plumbed as the thermal-bank, in the basement.

Keep in mind that you dont want water any hotter than 100degrees in the PEX. Circulating one loop through the heat-sources and thermal-bank. and a second loop from the first-loop and through the PEX tubing.

Thermal mixing valves are really cool!

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Old 09/27/06, 09:40 PM
 
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thanks for info.

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  #4  
Old 09/28/06, 06:47 AM
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I built an outdoor wood furnace to heat water. I used an old propane tank for the burn chamber, and welded a tank together for the water jacket that the propane tank sits in. I dont heat my water yet. I have a coil(it looks like a car radiator) in the hot air plenum of my existing forced air furnace. I have a pump that circulates the 180 degree water through the coil

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  #5  
Old 09/28/06, 06:48 AM
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Max
 
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Quote:
Originally Posted by ET1 SS
basement.

Keep in mind that you dont want water any hotter than 100degrees in the PEX. Circulating one loop through the heat-sources and thermal-bank. and a second loop from the first-loop and through the PEX tubing.

Thermal mixing valves are really cool!
why dont you want water temperature hotter than 100 degrees in PEX? My dad uses pex and his water varys between 140, and 180 degrees. He doesnt have any problem.
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  #6  
Old 09/28/06, 06:53 AM
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Unless there is a low rated PEX.... the stuff here is used in hydronic heating all the time at 180 f . On a closed system you'd want the PEX with air barrier. There's a thread in Shop talk on hydronics too.

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  #7  
Old 09/28/06, 07:03 AM
 
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We have pex plumbing and the water heater is set at about 120. No problems.

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  #8  
Old 09/28/06, 07:10 AM
 
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Rust is a big enemy. Put an additive in the water to prevent Rust. Jay

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  #9  
Old 09/28/06, 10:57 AM
 
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Exactly which material you intend to put in concrete is not clear from your post. If it is anything other than Pex tubing or a similar product made to be put in concrete then I would advise against it.

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  #10  
Old 09/28/06, 11:16 AM
 
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There's more than one kind of tubing used for infloor heat, PEX is only one. You need to research which type you want to use. We did not use PEX.

The infloor saves a lot of money. Instead of a furnace and hot water heater, you only need the hot water heater. If we could have managed it around the plumbing/heating inspector (very conservative guy) we would have an outside maize burner. Corn is so cheap, readily available here, and if needed, we could grow our own.

What we need now is a generator. Without electricity we loose the pump and eventually the house cools down.

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  #11  
Old 09/28/06, 11:27 AM
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Kytec tubing is another type, it has an aluminum core inside plastic. Great stuff but pricey

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  #12  
Old 09/28/06, 11:46 AM
 
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Quote:
Originally Posted by Ole Man Legrand
Rust is a big enemy. Put an additive in the water to prevent Rust. Jay

Open systems (no pressure, the vat of water is open to the air) keep disolving oxygen into the water, & are more prone to rust issues.

Closed systems (lightly pressurised, has an air expansion tank) does not introduce new water or air very often. In these the water turns blackish, and the oxygen leaves the water. These don't need rust prevention - they automaticly take care of that issue. You want the special PEX or other types of tube that prevents oxygen to pass through.

--->Paul
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  #13  
Old 09/28/06, 12:05 PM
 
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One of many families that I know that put in radiant floor heat, used an LP/propane water heater for domestic hot water and the heating, and a 12 volt DC pump for circulation. The pump ran on a large truck (semi?) battery and needed charging once a week or so. A small PV panel would have taken care of keeping it charged. It was the only electrical item in their home, and they were planning on adding PVs, but they moved.

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  #14  
Old 09/28/06, 02:16 PM
 
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Make sure you add a t/p valve.

A coworker bought a house with a hydronic system that ran through the fireplace, but the previous owner didn't put in a pressure relief valve. His daughter was sitting in front of the fireplace when it exploded. Chunks of brick went through the drywall across the room but miraculously she wasn't hurt.

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  #15  
Old 09/28/06, 02:24 PM
 
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If the system is open and also used as the hot water supply, you would likely want the temperature up above 120-130. If the water is continuously replenished, AND the water is hard, you will have calcium, magnesium, silica deposition at the area of highest heat...nearest the burner. Fact of life. You can get away with it if it is softened water. But an initial fill of same water and used as a closed system, the hardness WILL deposit but only a light dusting of scale. That scale will help reduce corrosion. If it is closed, I highly recommend an additive. Prestone antifreeze is cheap and works sufficiently well...for a closed system.

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  #16  
Old 09/28/06, 06:45 PM
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Quote:
Originally Posted by michiganfarmer
why dont you want water temperature hotter than 100 degrees in PEX? My dad uses pex and his water varys between 140, and 180 degrees. He doesnt have any problem.
I do not know why.

My PEX says that it is okay for up to 240 degrees.

Though I have spoken with the local plumbing supplier, as well as a retired plumbing contractor that works in the plumbing department at HD; both gentlemen were insistent that you plumb in a mixing valve, to regulate the loop's water to 95 or 100 degrees. They both seemed to express that plumbing a baseboard is totally different from plumbing radiant flooring.

I assume, that it is a matter that baseboards can safely be 200 degrees, and you would never know it. Whereas if your floor ever got to 200 degrees, you might not like it.

I am using the oxygen barrier tubing, though as it turns out, I really did not need to.
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  #17  
Old 09/30/06, 01:06 AM
 
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I'm full of advice, but it's hard to visualize what you're doing. Some people would build a McMansion in the woods and call it a "cabin". Other people use the same word when they mean "made with found materials."

Radiant heating has been around since the Romans built baths, but in our time it was discovered by Frank Lloyd Wright in Korea. (The Japanese to this day call a heated floor "a Korean room".) The Koreans used wood heat and simply ran the flue under the house. I cringe at the mention of water because almost everything with water in it eventually leaks and a leak in the floor can be very hard to fix. Running hot air through a floor is a lot cheaper and not so likely to become a problem later. (I would not run flue gases through there for any reason!)

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  #18  
Old 09/30/06, 08:03 AM
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Something that I first saw in Europe, and later installed in our MFR in Ct, is towel-warmers in each bathroom.

When plumbing baseboards or radionic floor systems; include a run up into the bathroom through a pipe 'ladder'. Rungs can be a foot apart, and can be anywhere from waste height to shoulder height. If you put a air-bleeder valve at the top, it will seperate all air mixed in the system and collect it for you.

The ladies LOVE warm dry towels within arm's reach of the shower stall!

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  #19  
Old 09/30/06, 10:04 AM
 
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Quote:
Originally Posted by SmartAZ
The Koreans used wood heat and simply ran the flue under the house. I cringe at the mention of water because almost everything with water in it eventually leaks and a leak in the floor can be very hard to fix. Running hot air through a floor is a lot cheaper and not so likely to become a problem later. (I would not run flue gases through there for any reason!)
I used to live in an old house that was originally from a Japanese internment camp from WWII. It was leaky and cold, but had a full basement. I put a big homemade woodstove in the basement and kept it going all the time, and the uninsulated floor radiated heat and made it the most comfortable house I ever lived in.
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  #20  
Old 09/30/06, 10:14 AM
 
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Not to hijack this thread, but this is home made radiant heat question too. We need supplemental heat in the back of our house and are considering pex tubing in the floor. We have one water heater and would like to use our hot water from that for the heat and also for domestic use. If we came off the hot side, thru the pump and tubes and then back into the inlet side of the heater, wouldn't that be alright? We keep the heater set around 120 degrees.

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  #21  
Old 09/30/06, 10:35 AM
 
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Quote:
Originally Posted by Ed Norman
Not to hijack this thread, but this is home made radiant heat question too. We need supplemental heat in the back of our house and are considering pex tubing in the floor. We have one water heater and would like to use our hot water from that for the heat and also for domestic use. If we came off the hot side, thru the pump and tubes and then back into the inlet side of the heater, wouldn't that be alright? We keep the heater set around 120 degrees.
Ed---I am sure you would have to do more than just that-------without valves that turn on and off --------your heat would be on all the time---plus in order for your tubing to heat up--you would have to move the water inside the pipe. I have never hooked up a system------but am interested in making one---have already collected most of what I need to build a outdoor water heater. Good Luck to you and I! Randy
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Old 09/30/06, 11:17 AM
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Make sure you use the correct pipe spacing for the water temperature you select

In-floor radiant heat design is based on several temperature-strategies;

  • 140 F max temp
  • 100 F max temp
Each of the 4 or 5 various design ideas and types of plastic pipes have different spacing requirements. The lower the temperature, the closer the spacing allowed.

The spacing and temperature of the water determine the PANEL (surface or floor) TEMPERATURE. The maximum panel temperature must not be greater than 85 F. If it is over 85 F then there can be foot problems -- various, athlete's foot, etc.

The heat loss of the space is calculated using standard methods. Each surface temperature and area are calculated and a MEAN RADIANT TEMPERATURE is determined. From this and the water temperature the proper spacing is looked up from charts.

Basically the RADIANT IN-FLOOR PANEL radiant temperature offsets the surrounding mean radiant temperature, so you feel comfortable. Radiant floors are nice; the space temperature can be lower than conventual and yet you feel warm. I like radiant floors, but I love my Blaze King wood stove.

You can most likely get the PEX pipe supplier to provide the correct spacing based on your building.

Good Luck,

Alex
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  #23  
Old 09/30/06, 11:31 AM
 
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Quote:
Originally Posted by Fire-Man
Ed---I am sure you would have to do more than just that-------without valves that turn on and off --------your heat would be on all the time---plus in order for your tubing to heat up--you would have to move the water inside the pipe. I have never hooked up a system------but am interested in making one---have already collected most of what I need to build a outdoor water heater. Good Luck to you and I! Randy
Whoops. I was keeping it simple for the post. I planned to put a check valve at the return line to inlet junction, and of course a thermostat upstairs to control the pump. Then I want a flush valve and a way to blow in air so I can drain it in the summer. And now I want a heated towel rack for some reason.
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  #24  
Old 09/30/06, 05:52 PM
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zone 5 - riverfrontage
 
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Ed-

LOL

Yes that should work.

It never hurts to please the wife. "Oh honey I saw this idea and I just thought that you would like it, I wanted to make you happy".

LOL

I have seen systems with just: a 40-gallon water-heater on the outlet a 'T' with one lead going to domestic hot-water, and the second lead going to a pump, then the PEX, then a check valve and back into a second 'T' at the water-heater's inlet.

Our system is a bit more elaborate but the same idea.

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  #25  
Old 09/30/06, 06:08 PM
 
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Question

ok, now be gentle because I have not yet read any books on this subject, but know I want radiant heat. Why can you not use a gravity feed solar box set up. the black tubing in the box heats water which makes it flow away which pulls up the cooler water from the floors that have given off thier heat load etc. a release valve and a way to cover the collector so that you don't have hot floors in july? Condensation? is it a problem. Anyone recommend a good read on the subject. thanks

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  #26  
Old 10/01/06, 06:44 PM
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zone 5 - riverfrontage
 
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Gravity feed?

From a stream? at 55 degrees, the solar panel adds ten degrees, so you r heating your home with 65 degree water. Not enough heat.

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