Connecting Baseboard to Pex

VT_MJT

Backstory: I will be installing hydronic baseboard heaters in my cabin soon. The local plumbing supply sized the baseboard for me, but primarily sells the Propex fittings. I already have the tools for crimp rings from installing the water lines, so would like to go that route and simply purchase the fittings and rings from Home Depot. I do have some experience from moonlighting with a plumber many years ago, but we ran all the lines in copper.
Questions: I cannot find any information on exactly how to connect the pex to the baseboard. I envisioned sweating a brass 90 to the baseboard, with sweat one side, barbs on the other, but then the pex would have to pop up thru the floor. I did read that this does not always come thru the floor straight. Is this OK, and will the pex make corner below the floor? I could sweat a copper 90 and run copper down thru the floor... and then the 90 sweat x barb within the floor cavity below? What are the recommended fittings for this application? Are there any 90's with a long leg which would help? I have done quite a bit of 'googling' and have not found a good detail or description of the 'typical' install. Thank you much!!

Ironman

PEX crimp fittings should generally be avoided in hydronic systems because they choke flow and allow O2 ingress into the system.

Also, O2 barrier PEX is essential for the same reason. Don't use regular plumbing PEX.

If you just used one, maybe two crimp fittings in an entire loop, that would be okay, but using them in a series loop at each baseboard will produce too much resistance to flow (head). A hydronic system operates with a circulator that produces about a 5 psi differential, not the 60 psi differential that happens in a potable system when a faucet is opened.

I'd see if you could rent or purchase the expansion tool. It's not that much in cost in the whole scheme of the project.

VT_MJT

Ok, so maybe Propex is the way to go after all. There is a lot of advice saying to use O2 barrier Pex across many forums and videos, no problem there. Would you have advise on running pex up thru the floor to connect to the baseboard, or would you run copper thru the floor?

Jamie Hall

Another factor. Even Propex gets floppy when it gets hot, so you will need to support the runs in the basement at very frequent intervals -- perhaps even in a channel -- to avoid that festooned with pipes look.

VT_MJT

Thank you everyone. It would seem that to add sleeves I'm going to need many to run thru all the floor joists and floor itself for the stub up, and the sleeves result in much larger holes. Now I wonder about compromising the joists. I would also need a 1 1/4" hole up thru the floor to account for the sleeve? Do the end caps cover the hole or does it become visible ? Now I wonder if copper stubs ups are the way to go. I'm surprised there isn't a "standard" for this joint, so much of the rest of the system is nailed 100%.

Ironman

PEX through the floor or joist is okay. Drill 1 3/8" holes and use the plastic grip bushings available from any plumbing supply.


https://www.supplyhouse.com/Viega-55140-3-4-Tubing-Insulator

Ironman

The bushing are installed AFTER the PEX is run.

hot_rod

A cabin, what size? Did you do a heat load calc. I've found buying straight lengths of pex makes the baseboard connection easiest, or run copper thru the floor and make the pex connection below.
Allow for expansion and contraction of the pex also, it will work against any holes thru the floor, allow some movement room in the pex. Plan on a lot of expansion if the pex goes from 55- 180° F