[Greenbuilding] [BULK] Pex tubing

[Lawrence Lile]

Might copper tubing be a good choice for the solar loop, especially if
it is glycol? Do you have a source for the Pex-Al-Pex?  

--Lawrence   




-----Original Message-----
From: greenbuilding-bounces at listserv.repp.org
[mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of Keith
Winston
Sent: Wednesday, July 19, 2006 9:09 AM
To: Greenbuilder list
Subject: [BULK] [Greenbuilding] Pex tubing
Importance: Low

Regular Pex tubing is somewhat standardized these days. You can use
fittings and tools between many (though not all) brands. It's
temperature rating is well below what solar wants: the top working
temperature of most Pex is around 180F I believe, and to have some
margin for error I'd like my solar umbilical tubing to be capable of
handling something more like 250F. I am currently preparing to
experiment with Pex-Al-Pex, which has considerably higher operating and
burst temperatures and pressures. It consists of alternating layers of
Pex (cross-linked polyethylene) with an aluminum core. It's stiffer, and
holds a shape, and doesn't kink as easily as some Pex'es do. But all the
Pex-Al-Pex manufacturers still have proprietary fittings, tools.

There are several different ways to cross-link polyethylene, which
result in different strengths, etc. Also, in heating systems some people
argue the necessity of an oxygen barrier, which can also be done several
different ways. At least one reputable company, Radiantec, suggests it's
unnecessary. Pex-Al-Pex doesn't require an additional oxygen barrier,
the Al works as one.

Finally, I spec'ed out a house in Pex fairly recently, for the potable
water, and subsequently decided I probably won't again. Upon catching up
on the literature, I was reminded that over and over we discover strange
chemicals that outgas and leach out of plastics, which very subtly mess
with our systems. Polycarbonate is used for laboratory animal cages, and
only when a researcher discovered a slew of results that they couldn't
explain, did they eventually discover that the cages were releasing
hormone-like chemicals. I think it was traced to improper cleaning
chemicals. I will likely continue to use Pex for heating systems. Also,
an experienced plumber running pex for the first time may not move much
faster than they could in copper (learned the hard way). Of course,
copper is getting very expensive, and copper mining is a scourge, at
least sometimes. Complicated world...

Warmly, Keith




> We used the PEX system in a recently built house.  I believe every 
> positive thing Lawrence has to say about it is true (chlorinated water

> is not a problem).  But be aware there are several 'systems'
> out there and the tools required to compress the rings (to hold the 
> fittings together) are proprietary to the specific system.  PEX tubing

> comes in several sizes btw.  I gather it can not be used for solar hot

> water because it won't expand properly.  Let me know please if I'm 
> wrong about this latter point.  Sacie Lambertson
>
>
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--
Keith Winston
Earth Sun Energy Systems
3927 Madison St.
Hyattsville, MD 20781
301-980-6325
keith at earthsunenergy.com
www.EarthSunEnergy.com



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