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

[Tom Lane, Energy Conservation Services]

good work -the key factor is that the pump starts circulation at 200 watts
per square meter and keep the delta t at less than  20 degrees  Fahrenheit-
up trought 1000 watts per square meter   if you keep the pressure high
thier is reduce chance of vapor lockand you can have up to a 25 degree
delta t  this assumes you are using flat plate collectors  gator tom----
Original Message -----
From: "Allan Sindelar" <allan at positiveenergysolar.com>
To: <RE-wrenches at topica.com>
Sent: Wednesday, April 09, 2003 7:56 PM
Subject: Re: AC circulator vs. PV driven DC [RE-wrenches]


> 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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