Radiant Heat Manifolds - How many?

reekasr

Maybe can answered but not sure how much info anyone would need. I am going to run radiant into my garage 26x24, room above the garage which is obviously 265x24 too and my main house which is about 24x40 one floor. Just curious as if its more common to run one manifold or 3 separate manifolds. I am still in design/budget phase. I will have 3 different thermostats (garage, room above and main house). I will try to keep run sizes close to the same but I have to see how close i can do that. House is located in Southern VT.

The reason I ask is because the contractors in this area slap stuff together and walk away, that's if I can even get them to show up. Its a real PITA. I have ran a radiant system once before in a 26x24 room above a garage at another home. This is the first time that I will have 3 separate heating areas, hence for my question :-) as I want to do it the right way.

hot_rod

Are all zones getting the same supply temperature?
I suspect the garage is a slab, and usually the lowest temperature requirement. That manifold may need a mixing device. Manifold placement depends on how centrally located you can place the manifold. You do not want a bunch of long leader lengths. Sounds like at least 3 locations?

GroundUp

Are all these spaces adjacent to the mechanical room? I prefer to run remote manifolds for zones not adjacent, to avoid running extra tubing through another zone that may not need heat at the same time. If I understand your scenario correctly, I would use 3 separate manifolds

reekasr

Yeah the pex will be in the slab in the garage. Basically the heat in there will be just to keep the place from freezing solid :-), never will be cranking it too warm unless I am working on something in there. So with that said, the zones will not be the same temp. Lets say zone1=garage, zone2=room above garage, zone3=mainhouse. Zone2+3 will be the same temp. However zone3 will only be running when I am away, since the wood stove will be the primary source. The "plan" for the manifold is in the basement which is 2 foot from the garage wall, about 10 feet from room upstairs (since Id have to come down the garage wall) and about 2 foot from where main house since its all right there under the main house. However, I can design it any way that I want, those were just my thoughts.

reekasr

The spaces are adjacent to the mechanical room. Room above garage is the furthest due to the garage ceilings at around 10 feet high.

GroundUp

Temp doesn't matter, that's what the stats are for. If 2 zones will be the same air temp at all times, you could combine them into a single zone and balance the loops accordingly. Would personally still use 3 separate manifolds however, given the bonus room is so far away

hot_rod

often times garage tube has glycol for freeze protection. So either the whole system becomes glycol , not my first choice, or a plate heat exchanger separating the garage from house.

Ironman

Have you done a load calc? I mean a scientific one like an ACCA Manuls J or similar, not some cheap online guesstimater. That's the first step. It's the foundation for all designing and sizing.

SlantFin has a free app you can download that is reasonably accurate.

reekasr

No load calc. I will see if I can find the SlantFin one for sure and get the calcs.