Solar Fluid Diversion [RE-wrenches]

[Allan Sindelar]

Wrenches,
On the solar thermal topic of a thermally activated diversion valve, I forwarded Peter Talmage's message to Bristol Stickney, a local colleague of mine who has done such work for decades. His response is worth sharing. It follows Peter's original post below.
Allan at Pos E

 > ----- Original Message -----
> From: "Peter Talmage" <ptalmage at yahoo.com>
> >
> > Another solution to draining out solar fluid is to use
> > a thermally activated diversion valve to allow hot
> > fluid to cool of in a loop of baseboard hydronic
> > elements. The valve simply sits in the return line.
> > The amount of diversion increases as the solar
> > intensity rises. We use these in our systems to ensure
> > that during the warmer months or when folks leave home
> > for 2 weeks in the summer the heat transfer fluid
> > stays nice and "cool". Check out   www.fpevalves.com
> >  and  www.rostravernatherm.com/ThermalValve.htm.
> >
> > Yours,  Peter Talmage

Hi Allan,
This is good information, although it is not a new approach. I did not know that these valve models exist, and only the installers can tell us if they are reliable after at least 2 years of operation.

This approach to overheat protection is known as thermo mechanical thermal diversion. Back in the early 1980's, I was involved with the importers of the French "Priosol" valve, which was one of the most accurate and precise thermo mechanical diversion valves ever made. I personally installed dozens of them in similar heat control installations. The problem is that eventually they always fail. The cooling port will stick open or shut. And so the question is: Will the failure be noticed before it causes cascade failure to the pumps, valves and other components? And will the failure occur long before a system designed without this valve, using some other approach?

The most reliable hydronic passive thermal diversion system may have been the Zomeworks "Tide Tank". This design never failed unless the boiler fluid leaked out completely below the level of the "tide tank". No parrafinnic thermal valve can be expected to be as chronically trouble free.

I do not know how reliable these valves are in solar applications, but I would ask anyone with five years of maintenance and repair experience with these valves to respond. I stopped using the Priosol valve after the first two years of enthusiastic promotion, because of maintenance and failure consequences.

Bristol.




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