sizing pex home runs to radiator

Home Depot Employee

Excellent idea Scott on adding a few plates here and there on the returns. I would imagine a few chosen spots such as in front of sinks, outside entrances are appreciated.

Mike F

sizing pex home runs to radiators

I would like to run 3/8 pex home runs to a mix of ci and panel rads. the largest of which is 7500 btu's . Am I making a mistake not running 1/2.

Timco

I run 2-pipe zones all in 3/4 to CI rads.

Tim

Home Depot Employee

Unless it is a rediculous long run, I don't see why 3/8" wouldn't work in your application as the rad requires less than 1 GPM.

Save your money on the larger PEX

Brad White_200

I use 5/8\" Pex-Al-Pex

and not just to be different...

The OD is the same as 3/4" copper so is easy to support with clips. Holds it's shape and the flow characteristics are wide enough to handle the smallest to the largest radiators. I even have served two large radiators via a 1.25" old gravity riser from a single 5/8" circuit.

Everyone has choices.

hot_rod

3/ 8 or 1/2

would carry ,75 gpm easily. 100 feet of 3/8 flowing .75 gpm of 160F water would have a pressure drop of 8.5 feet of head. easily within reach of a typical 80 w circ.

At a 35 degree delta T in the circuit, common in Europe, you could move 15,000 BTU/ hr @ 10.7 feet of head pressure drop.

Consider TRV's and a delta P circ for the best efficiency on the distribution side.

Unknown

and PEX-AL-PEX to reduce noise issues!

It's pretty rare to need more than 1/2" pipe for any single, dedicated radiator.

scott markle_2

Nothing pulls or handles quite as nice a 3/8. Two pipes pull smoothly through a 1.125 inch hole.

Noise is not much of an issue in constant circulation systems. Temperature changes are gradual and don't cause the rapid expansion noises that can occur in on/off regulated systems. Full reset constant circ. also makes me more comfortable with the possibility of long term pex chaffing issues.

I'm doing a 3/8" home run panel radiator job right now. On some of my shorter runs I'm extending my return leg a bit and doing extruded plates for a little bonus radiant in selected areas.