solar thermal pumps [RE-wrenches]

[Smitty]

Kurt, for what it's worth, Richard Lane and I have conducted some tests
of various pumps moving glycol and water at the large Packerland system
(R.I.P.) in Green Bay. I am assuming this system is going to be in
northern Wisconsin. What we found is that in the dead of winter, with
very low temps, the glycol will start slushing and even become a
semisolid ice plug, but not enough to pop anything. At daylight the
panels tend to thaw out, but the glycol in the insulated above ground
plumbing remains semi frozen or very thick. The DC pumps we tested had a
very tough time with this. Sorry Dan, but the El Cid just didn't cut it
with semi frozen glycol. The Hartell did a bit better but in the final
analysis I would use an AC pump and a differential controller if
possible. A few days of the year, we would even have problems with the
Packerland system, and that was with 6"-14" pipes and many 10 hp pumps
(5000 collectors). If you go DC, I would oversize the PV panel to
accommodate morning incident angle, so it at least it has chance of
getting the glycol moving.

The panels should be plumbed in parallel.

The smaller a pipe is, the more frictional wall loss there is. 3/4" is
the smallest I would use. Hope this helps. Smitty.

Kurt Nelson wrote:

> Greetings all (and Smitty?), I'm doing a solar thermal system/in-slab
> hydronics, and though I have done a number of SDHW systems, I'm new to
> moving fluid through larger arrays. The collector is 5  (possibly
> six), 4x8 Solar Kings ground mounted about forty feet from the house.
> I would like to run the pump(s) PV direct and it would seem that there
> is a shortage of pumps to choose from here.  I was thinking two Hartel
> HEH-10's (did I get the model numer right) and would welcome other
> suggestions.  Also, .... 1 - Is it best to plumb (pipes) them in
> series, or parallel?2- Is it best to wire them each to individual
> 18-22 watt panels (my guess) or both to a single 38 to 44 watt panel.3
> - The burried and insulated piping from the array to the house....  go
> with 3/4 inch pipe (or even larger) to accomidate flow, or 1/2 inch to
> reduce heat loss from piping surface area AND the increased time the
> heat transfer fluid spends in the pipe? Thanks in advance for thoughts
> and suggestions.Kurt NelsonSOLutions
>
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