AC circulator vs. PV driven DC [RE-wrenches]

[Allan Sindelar]

----- Original Message -----
From: "Jeffery Wolfe, Global Resource Options"
<jeff at globalresourceoptions.com>

And who needs to remember to get the brushes replaced
> BEFORE the collector stagnates?
Good point, Jeff. In this case, we are handling ongoing electrical
maintenance on this job, so that issue (brush wear) will be our
responsibility.

And then when the unskilled plumber goes to "fix" it in 5
> years, he'll have a clue.
And the installing plumber is also on contract for plumbing maintenance, and
we have a good history with this plumber.
>
> Guess we've found that to be less of a problem than the DC pump non-power,
PV panel covered by snow, PV panel
> clear/solar thermal collector covered by snow...
Both collectors and PV are set to 75 degrees off of horizontal, in order to
maximize winter gain and control summer gain. Snow won't stick. New Mexico
is a very different climate than Vermont, and with anything solar, one size
never fits all.

> ...flat plate panel running at low startup temps while full sun is on the
PV, etc. problems.
This issue has been discussed here previously. We could have added a
low-limit snap switch for this, but chose not to in the interest of
maximizing simplicity and thus reliability. Even a snap switch is simpler
and thus has potentially less to fail than a differential controller.
>
> Certainly for a larger system, getting enough DC pumping will be a
> challenge, unless the tank and pumps are right at the collectors. This
will
> result in a "small plethora" of DC pumps and PV's. Just seems simpler to
put
> in an AC pump.
For us the DC centrifugal covered our needs, one pump and 150W of PV per 8-9
panels. There are a total of four systems on this client's ranch, spread
over three separate buildings. Two of the systems are all AC, *except* for
the PV-direct primary loops. The other two are part of an integrated 48V
power/heating system. The AC systems have been in for two heating seasons,
the DC most of one. OK so far--we'll see.

Always many solutions, and no one clear best and only way to do something...
>
> Enjoy spring!?
Yes! Hope you are too.
>
Allan @+E

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