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

Allan Sindelar allan at positiveenergysolar.com
Wed Apr 9 16:56:38 PDT 2003


Peter,

You have a smart customer.

We did this very thing using 9 4X10 collectors, two systems. For each bank
of 9 collectors we used a Dankoff SunCentric 12V centrifugal pump, model
7323 with high temperature option, running array-direct without LCB on 150W
of PV, with the array tilt angle matching the collector tilt angle.
Insulated 1" copper buried lines. No disconnect, I don't think there was
even a fuse, as we never want the pump to stop if the sun's shining on the
collectors. Size the pump carefully to optimize head and flow, and note
voltage drop at 12V with that motor--centrifugal pumps have specific
requirements to run optimally.

One of the two pumps was stiff when new--some quality control issues with
Dankoff. It would stick on morning startup, and once allowed the collectors
to stagnate and blew off the PRV. Whatta mess of expensive Cryotek! The pump
was fixed or replaced under warranty and it's been OK since.

I would not recommend an AC differential controller if you're on grid. One
daytime grid power failure and you;ll stagnate and blow a PRV--or worse.

Hope this helps.
Allan @+NRG

----- Original Message -----
From: "Peter Talmage" <ptalmage at yahoo.com>
> I am designing a solar heating system which will use
> 10  4'x10'collectors. I had planned to use a single AC
> pump operated by a differential controller. The system
> uses antifreeze so there is only modest head to
> overcome. My customer likes the reliability of a DC
> pump driven by a PV. I usually do this with small
> systems, but this one would need 4 Hartell pumps to
> get adequate flow, considering head loss. Anyone have
> any thoughts ?  Thanks.

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