Manifold Placement for In-Floor Radiant Heat in Multi-Story House
I am attempting my first in-floor radiant heating setup in a multi-story house and I am having trouble finding information on where to put the manifolds. There are three floors, plus a basement. The 3rd floor is a conditioned attic with a chase running to the basement to supply forced air to the attic and 2nd floor.
I can easily put the manifolds for the basement and 1st floor down in the basement. My question is, Where is the best place to put the manifolds for the 2nd floor and attic? Should I install the manifolds in the attic to minimize the number of piping running to the basement or run every loop to all of the manifolds in the basement?
Thanks in advance!
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If you have space for a utility area in the back of a closet or laundry room I'd do a manifold on each floor. You're going to have to have the zone valves on the manifolds and they're going to have to be accessible. On an interior wall you can cut out the drywall to make an access panel.
If you already have a chase for ductwork I'd try running the big pipes along them and having the manifolds nearby.
Manifolds take no space. I had mine tucked in closets You want them near the floor being heated especially if you are using small diameter tubing. ISTR having more than one loop in a ~140 sq ft bedroom due to loop length limitations. WHy have 20+ feet of tubing not heating the floor to get to a distant manifold.
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That makes perfect sense. I thought this would be the right way to do it, but I just wanted to make sure. Thank you very much!
Do the larger supply lines going to the manifolds count towards the 300’ limit on the loops in the floor? Should these be insulated to minimize heat loss?
You have to understand where the 300' limit comes from. Two things: you don't want to have too much resistance in the pipe, it limits flow and requires a bigger pump. Also, you don't want to have too much temperature drop in your pipe, it leads to uneven floor temperature.
At 8" spacing 300 feet serves 200 square feet of floor. Half inch pipe can handle about 1 gpm. At 1 gpm with a 10F drop you're delivering 5000 BTU/hr, or 25 BTU/hr/sf over 200 square feet. That's a floor temperature 12.5F above room temperature, which is a nice feel.
The pipe leading to the manifold does contribute to the resistance, but it doesn't contribute to the temperature drop.
No, they don't count to the length rule of thumb per loop.
Yes, insulate the supply lines if possible. But probably not a big deal if not. Depends on where the heat is being lost to.