Hey there, I'm getting ready to finalize my radiant floor heat system and would appreciate some advise. I have 7 rooms different zones (joist trak w/ 1/2" PEX-AL-PEX) and they're all over a pretty big single floor. Also, the location of the boiler needs to be in the mechanical room that is furthest away from all 7 zones as possible. Instead of having one 7 port manifold in the boiler room and have 14 way to long runs of 1/2" PEX, I was planning to do the following: - 2 manifolds (1x3 and 1x4) close to the zones as possible, like in the closet of one room - 1" pex as supply and return from boiler room to each manifold Is this a typical set up? Any concerns with the above? Also, would 1" be recommended or should I go even bigger? Thanks, Tim

one additional thought:
would it make sense to run supply to the first manifold, from there to the second manifold and run return from second to boiler? Could I use a single pump with that set up?

-Tim

1 BTU will heat or cool 1 pound of water 1 degree F. SO the problem here is how many BTU do you need to move per hour to heat your building. With that information we can figure out what kind of flow you need thru that main line to meet the need which will determine the line size needed and pump rate.

As for two separate manifold pairs(supply and return), the main boiler supply feeds to and thru the main pipe of the first manifold and on to the second manifold where it ends(outlet of manifold capped, usually with a service port and air vent). The return manifolds would work the reverse of this, with the main line connecting to the farthest manifold(capped on far end), and run back to the other manifold, passing thru it's main ports and on to the boiler return. IF the main line is well insulated, I see no real problem with this. Visualize taking a set of 7 port manifolds, cutting them between loop ports 3 and 4 and extending that pipe between port 3 and 4 with insulated PEX... The supply feeds the 3 and 4 port manifolds and all 7 loops. The 7 loops return to the other two 3 and 4 port manifolds and back to the boiler. The added fluid resistance between the two manifolds may effect how you have to balance the loops, but again I do not see that being a really big issue unless the first manifold is really close to the source/pump...

heater will be 27k BTU
- 50' from heater to first manifold
- 30' from 1st to 2nd manifold
- 50' from 2nd manifold to heater

in addition to the size of the tubing, would you have any recommendation on the type? It's doesn't need to be pex-al-pex for the supply and return line, right?

Thanks,
Tim

We use and highly recommend Uponor HePex (PEX-a, having the highest degree of PEX crosslinking) and ProPex fittings for all our HR installations.

thanks for the response!

I already have pex-al-pex tubing for the radiant itself but need advise on tubing between boiler and manifolds.
Would 1" be appropriate? What type of tubing should I use between boiler and manifolds?

Thanks,
Tim

The rules of thumb indicate that 1" of barrier PEX is fine for the distances and BTU/GPM you have.

thanks!

sorry, one more question:
what pump would you recommend for my set up?

Thanks,
Tim

Without proper analysis or reliability data (ie, a guess) - a Taco 007e. I would pay a professional to review your entire design.

Jon is right.

Design-by-internet is not advisable.

Any barrier PEX will due and 3/4" is fine given the information you gave us.

Uponor hePEX is a premium cross-linked polyethylene. It is fully cross-linked when delivered. HeatLink is also and "A" PEX and we use it as an equivalent regularly. I have both in my buildings and have used "B" and "C" PEX with perfect results.

You will find the cost and handling qualities of 1" PEX is not something you want to volunteer for unless someone has done he math.