Quote:
Originally Posted by Minimac
It's been my experience that there are much better ways to do this-especially in an older home - than using Pex. Pex itself is cheap but by the time your done with a mixing valve, clips, pans, manifolds, etc., it isn't inexpensive. IMHO, a much better way is to run fin tube(without enclosures) in the space between the floor joists. Even if you only do every other joist, you'll end up with a well heated floor. I divert a line off of a return before it goes back to the boiler and hit 4 or 5 joist spaces, then back to the boiler return line for that loop.
You're pulling heat from the return that would normally just dump back to the boiler. Your heating line should be leaving the boiler @ somewhere between 180*-190* and even if it's returning at 140*, that's better than you can do with Pex.
I don't mean to offend anyone,especially in my first post here, but to me, Pex is glorified garden hose.
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Boilers are not intended to have such as high dT (20F is the norm and 30F for commercial DHW boilers is norm) and any boiler that needs to run at 180F is not as efficient as can be. Copper fin boilers will have more expansion than designed for if they run at such as spread. Not good for cast iron either.
The goal with any heating system is to run as low temp as possible to be efficient. That said, I once did 20 houses using copper fins as you talk of, and they were up in Fort Francis, Ontario (-40C no problem) and run off a water heater. We placed them in the perimeter joist spaces and let them radiate up. They were low energy houses and I can't remember how many feet of fin tube there was per house but it worked (it was 20 years ago).
PEX has its place which to me is in an embedded slab although I have used it for almost everything short of steam. Wirsbo tubing (Uponor now) used to talk about taking a piece of PEX (in the late 60s when it was developed) and
which was placed in a steam heat test at steam pressure. Every month it was removed and measured and since that first test till the mid 90s when I talked to them, it had lost 5% of its wall thickness. This is an extreme example of how a good cross linked tubing can be so in a floor application at 100-120F..........no worries. The biggest issue is O2 barrier.