Author Topic: Piping material from collector to storage  (Read 747 times)

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Offline tomasaur

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Piping material from collector to storage
« on: April 08, 2016, 04:55:21 PM »
I'm building a solar hot water system to help heat our hot tub.  I'm curious about what kinds of piping material would be appropriate from the collector to the tub.  The collector itself is made with copper tubing, and the control center (pump, expansion tank, pressure regulator, etc) is all plumbed with 3/4" copper pipe.  However, it would be handy to have something cheaper and flexible to go from this to the tub itself, and once in the tub cabinet, to loop around to the heat exchanger.  Would Pex be a suitable material?
Thanks,
Tom

Offline rossw

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Re: Piping material from collector to storage
« Reply #1 on: April 08, 2016, 08:50:58 PM »
Would Pex be a suitable material?

There's PEX, and there's PEX. Make sure you get one rated for high temperatures (hot water). Not all are, it seems.

I have a 60-tube evacuated tube solar collector, I run to and from it in PEX. I've lagged it (obviously), and it's not operating under particularly high pressure - just static head plus a circulating pump. It's a pressure-relieved system with a low-pressure relief valve, so only ever sees about 5m of head. Been running constantly for 5 years, never missed a beat.
I frequently have water right on the verge of boiling, running through it.

Offline tomasaur

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Re: Piping material from collector to storage
« Reply #2 on: April 09, 2016, 09:06:49 AM »
Thanks, that's very helpful.  I had seen folks say that Pex would lose any pressure holding ability above 180 deg F and that was a concern.  What I've read about the different types of pex (A, B, C) is that they all have to conform to the same pressure and temperature ratings, but that they differ in how they're manufactured, which in turn affects things like flexibility and of course, cost.  Theory aside, what I'm starting to hear from you and others who have used pex in real world applications is that it does a fine job. 

Offline eraser3000

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Re: Piping material from collector to storage
« Reply #3 on: October 03, 2016, 09:26:48 PM »
I quit using PEX after blowing it up several times.  Went to steel pipe and radiator hose, then moved on to stainless tubing.

Offline Wolvenar

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Re: Piping material from collector to storage
« Reply #4 on: October 05, 2016, 04:24:14 AM »
I have a hydronic heating system with pretty much the majority made with PEX tubing. It's a wood heated system, and has had more runaway conditions than I care to admit (fixed for good now). These have had the water mix well over 180F with no problems.
I have oxy barrier PEX with an encased aluminium jacket so that may be helpful for its resilience.
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline eraser3000

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Re: Piping material from collector to storage
« Reply #5 on: October 05, 2016, 08:39:39 AM »
I think the difference is that most systems run very low pressure. Because of high temperatures I've had to operate at higher pressure in order to get my heat transfer fluid to not boil at 250-275F.  During the blowouts I had, my RTDs registered 425F peak.

I use Pex inside for almost everything though.