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Wirsbo PEX for hot water...? - Page 2

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Posted by Steve Shantz on December 7, 2008, 2:54 am
 
John,

I agree with everybody else.  In normal operations, PEX would probably
work just fine, but you system will not always operate normally.
Sooner or later you will almost certainly stagnate with a mid
afternoon 1/2 hour power failure on a sunny day.  That first blast of
hot water will be nasty on your PEX.  You might consider PEX for the
cold line from the tanks to the collectors but you need to make sure
the hot cannot get into this line.

Also, PEX has a much higher thermal expansion coefficient than
copper.  PEX-Al-PEX is not as bad as plain PEX, but it is still higher
than copper. I'm not sure what the Wirsbo product is. A Google search
found a book "Modern Hydronic Heating for Residential and Light
Commercial Buildings" with a table of expansion coefficients (in/in/
F):
Copper          0.0000094
PEX-Al-PEX      0.0000130
PEX             0.000094

So a 50' run of PEX with a 100F delta T would expand:
0.000094 x 100 x 12 x 100 = 5.64"
PEX-AL-PEX would expand just under an inch, and copper would expand
1/2"

Steve

Posted by J. Clarke on December 7, 2008, 3:00 pm
 
Steve Shantz wrote:

If PEX can run 26 years continuously at 201F and 151 PSI I wouldn't
expect a single excursion to 212 to do much to it.


to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)



Posted by Rip on December 7, 2008, 10:39 pm
 J. Clarke wrote:

Since I've just turned my system on, I don't know what it's going to do
next summer. However, with collector stagnation temps of 205 degrees in
New England midwinter, I expect to see stagnation temps at least
somewhere around the factory setting of the "Emergency" temperature
function on the Resol controller I'm using. That setting is 285 degrees
F. (adjustable from 230-400 F). Not a PEX environment.

Rip

Posted by J. Clarke on December 8, 2008, 12:24 am
 Rip wrote:

Uh, you are not talking about a hot water system at that temperature,
you are talking about 53 PSI steam.  Is that your intention?

--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)



Posted by Rip on December 8, 2008, 2:41 am
 J. Clarke wrote:

Hi J. Clarke. I can see that you are one of those jerks that just likes
to argue with no real informational input. FYI, the solar loop on my
system is filled with 50% volume Dowfrost HD, and pressurised to 50 PSI
gauge, yielding a boiling point just shy of 300 degrees Fahrenheit.

I'd suggest you go build your system entirely with plastic tubing, and
get back to us all when your collectors stagnate. The entire point of
this thread was "Is Wirsbo PEX good stuff, and has anyone had experience
with the tooling to install it?"

See you all. My installation is complete and working. I logged into this
newsgroup to see if I could glean, and supply, any useful info, but as
usual on USENET the signal to noise ratio isn't worth the effort.

UNSUBSCRIBING now.

Rip

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