Radiant floor pex 1/2 inch

Ironacres58

If i had a 700foot single loop on a dedicated heat source would it still work in my slab with 2inch insulation under it ??

Derheatmeister

NO.. 700 foot on a single 1/2 " pex line is way to long !!
1. After about 250 feet you will stop unloading heat
2. You will need a very high head circulating pump to establish flow.

Now ..If you had 3 to 4 loops that may work
I would start with a heatloss calculation.

Ironman

No, that’s way too long.

As mentioned, keep the loops around 250’.

An accurate heat loss calculation is the foundation for all design work. How would you know if the floor could supply enough heat  if you don’t know what the actual heat loss is?

hot_rod

Do you? Have a 700’ loop in a slab?

If so, here is that loop with .50 gpm just under 9’ head, workable with a small circ

At .65 gpm it goes to almost 14’ head

I,ve helped out 1000’ loops by putting a flow reverser on them, supply hot from one end for 15 minutes, then switch to the other end. Keep switching direction every 15 minutes to help even out the slab temperature.

Zman

If you are one of the unfortunate folks that ended up with a 700' loop and are trying to find a fix, there is a trick where you use a 4-way reversing valve to help solve the problem.
You should never intentionally run a loop that long, it is very difficult to get enough flow, and most of the BTUs are dissipated at the beginning of the loop, leaving you with uneven heat.