Solar Hot Water Systems - PV vs delta T control [RE-wrenches]

[Todd Cory, Mt. Shasta Energy Services]

David,

Since you have an antifreeze loop you probably have 2 pumps in the system, unless you can get
enough convection on the potable side of the heat exchanger to effectively circulate. Anyway,
I have a 2 pump glycol system, and it is run PV direct. The glycol circulation pump is DC, pv
direct. The potable side of the loop also uses a DC pump off the same PV panel, but is
switched through a differential controller. Works great.

Hope this helps,

Todd



David Blittersdorf wrote:

> Question:
>
> We are in Vermont which gets real cold in the winter and SHW systems are antifreeze
> loop types. I have a Heliodyne system with AC pumps and a differential temperature
> sensor controller. I am looking at the trade-offs of going to the PV powered pump
> system vs the delta T control. I like the temperature sensor system as it will not turn on
> the pump when the stored hot water is warmer than the collector temperature. I have
> noticed in the very cold winter months that the pumps cycle on and off to make sure the
> incoming collector water is at a higher temperature than the tank.
>
> I can forsee a problem with the PV powered pump happly pumping cold water into a hot
> tank because the PV panel is very efficiently running the pump (cold temp.) but the
> collectors are not warm yet. I also notice that my PV panels shed snow quicker than my
> hot water collectors.
>
> Any experience out there?
>
> Thanks,
>
> David Blittersdorf
> NRG Systems, Inc.
> 110 Commerce Street
> Hinesburg, VT 05461 USA
> Tel: 802-482-2255
> Fax: 802-482-2272
> email: davidb at nrgsystems.com
> Web:http://www.nrgsystems.com
>

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