radiant heat from owb

[zsteinmetz]

Ok guys im gonna be putting up some staple up radiant heat under the floor joists in my kitchen. Now talking to some people they said I could just run 1/2 inch pex one per cavity(18 inches on center joists) stapled right to the floor with no heat plates and use the water directly from the boiler. No heat exchanger just add a couple valves to my return line and tap off that at 150 degree waterand add a pump. My kitchen is not real big and the total footage of pex i would be using at one per cavity would be about 250 feet. can this be done or should it be a separate loop with heat exchanger and expansion tank.

 

[MS-310]

I would try it! But I would use thin foam and put it on the floor joist...So its forcing the heat up. It mite get a little warmer in the kitchen then what you'll think.

Try it.

 

[ericjeeper]

Pex is cheap

Run 2 lines through every joist spacing. to be sure.. NO hx just direct

 

[crowbuster]

I ran my lines under the kitchen floor along the joists to get from owb to inside boiler. Holy mackerel was it ever way to hot. Kitchen, utility room and gun room especially were just unbearable. Have a partial basement the rest being open crawl space and i couldn't lose heat fast enough to not make it to hot. So i used the foam pipe insulation around all pipe, 1" pex, and used ceramic insulation around heat exchanger, much better and actually made owb work less not having extra heat loss. Thats just my experience yours my very. Best of luck to ya.

C.B.

 

[ktm250rider]

Im currently using AL-Pex in a staple up method just for floor warming on the tiles. The Al-Pex is stapled about 1 inch from the subfloor and then insulation fills the joist bays. The water coming into the system is about 140-150°F. I dont get very much heat. The system is supposed to heat the air space between the insulation and the subfloor. Then transfer the heat to the tiles. Air is a very poor heat transfer rate. Youll get better results with the aluminum plates with direct contact with the subfloor. I plan on adding plates to mine when I finish some of my other projects.

 

[zsteinmetz]

What size pex are you using? How many runs per cavity? What size pex? Do you think I could staple the pex directly to the subfloor so the pex is actuall touching the wood or within a 1/4 inch of it?

 

[blis]

What size pex are you using? How many runs per cavity? What size pex? Do you think I could staple the pex directly to the subfloor so the pex is actuall touching the wood or within a 1/4 inch of it?

it will always work better with those aluminium heatspreaders, althou some ppl prefer to not use becouse they want to save some greens but usually it leads to poor effiency...

 

[fourustircom]

Pex insulates!

I think if I were doing radiant heat, I'd run something metallic to transfer the heat. I just gor my Woodmaster 4400 going and had trouble with the Aquastat that keeps the oil furnace from kicking on due to the insulating ability of the PEX. Plan on the outside of the PEX being 10-20 degrees cooler than any metal connectors.

With the furnace in the basement, just above the furnace plenum where the heat exchanger is located, the pantry floor is quite toasty warm! That's with the depth of the joists even! My first experience with radiant heat.