Radiant Floor Heat Pattern and Manifold?

Mental

I'm about to do between joist Hydronic radiant heat. I was originally going to do the room in one big 450' loop. Then I thought about 2x 225' loops. Then I started to think, the cost to do a pile of loops on an "Unbalanced" manifold isn't really that much more expensive. So what if I make a line on the hot side with T fittings and then one on the return side as well?



Do any of you see a problem with this plan?
Do you think its possible that it would be better performance than just one or 2 loops?
Could it end up being worse performance?

Zman

I would go with the 2 loops.
It would be simple and easy to purge.

GroundUp

I did my own house like that, I think there are 26 or 28 loops only about 100ft long each. It is piped as reverse return and still needed some balancing valves in each loop but works great

Mental

Needing Balancing valves on each loop really brings the cost up. I was hoping to get away with having 18 loops in one zone and only having to balance the various zones. If I were to lean towards 2 loops *Stares sadly at crate of T's* Does it make sense for the loops to start at the outer walls and move into the center of the room, as far as heat balance goes?

So say 2 loops, one represented by orange and one by Red, with flow being opposite direction. Does that sound like a good Idea?

STEVEusaPA

If you can’t afford two balancing valves and two flow meters on the manifold, you can’t afford radiant heat.

Dave H_2

Do NOT make it one loop, otherwise you will need the Binford 9000 circ in order to move the water thru it.
Make it two loops, do NOT make it 20 loops.
The idea of using pex is because its flexible and easy to loop thru. Every connection you make is a potential leak.
If flexibility is needed, consider using 3/8" pex.

Mental

STEVEusaPA said:

If you can’t afford two balancing valves and two flow meters on the manifold, you can’t afford radiant heat.

Its not about 2 balancing valves, the initial plan would have ended up needing around 50

Dave H_2 said:

Do NOT make it one loop, otherwise you will need the Binford 9000 circ in order to move the water thru it.
Make it two loops, do NOT make it 20 loops.
The idea of using pex is because its flexible and easy to loop thru. Every connection you make is a potential leak.
If flexibility is needed, consider using 3/8" pex.

Does the pattern I have for 2 loops make logical sense?
Conceptually any two joist cavities should equal out to similar temperature across the room?

Dave H_2

@Mental
I would just split the room in half, one loop on each side. Heck of a lot easier to install.

The Delta T is typically 10 degrees, and then since you are heating the air pocket below, the surface temp of the floor will be pretty uniform.

hot_rod

The trade out is many holes drilled in the joists to go with two loops. Unless you loop under each joist. Looks bad and uses a lot of additional tube.

Another way is drill a larger hole in one end of every joist, cut a 250 loop, thread it through the large hole. Then pull a loop from that to the end of each joist bay. It's much easier then threading through each bay, only requires drilling one end of each joist, and gives you two tubes per bay. 3/8 pex works easiest.

hot_rod

Here is a clever model showing how to thread the joists with holes at one end. With two loops either one large hole with all tubes in it, or spread the holes 12" OC similar to what he did with one loop.

I've done this single handedly, much easier with an uncoiler and two people.

Check a hole drilling chart for where and how large of a hole you are allowed to drill in a joist.

What is the square footage of the room? Two tubes per 16" joist is about 8" OC. Room X 1.45 would give you the amount of tube required. With 3/8 tube 200' per loop. So divide that number by 200. No harm in having more loops as opposed to excessive lengths. 200- 225 for 3/8" 275- 300 for 1/2" is a safe length.

https://video.search.yahoo.com/yhs/search?fr=yhs-ima-st_mig&ei=UTF-8&hsimp=yhs-st_mig&hspart=ima&p=threading+radiant+pex+tube+in+joists&type=q3000_A1BWP_set_bcrq#id=4&vid=bfc78a2d54cb2ba134ef60007c2202de&action=view