[Greenbuilding] Solar Hot Water System

[Frank Flynn]

I have an older Open loop, drainback system.  Where the domestic  
water is circulated through the panels under normal house pressure  
and at night the system shuts off and the drain down valve is  
supposed to allow the water in the panels to drain out and (with an  
old hose) into my garden.

These were popular in the '70's and this one was working well until a  
week ago.  I have had problems with freezing over the years; I live  
in California where freezing is rare but possible.  We have just had  
a major freeze - and again one of the collectors has sprung a leak  
(hopefully in  the coupling not the panel itself).

I have read articles on other websites which agree that the drain  
down system is prone to this particular failure after some years.   
The problem is you don't notice that the drain down has failed until  
you wake up to a leak on your roof.

My thought at this point is to switch it to a recirculating system  
where the panels stay full of water and when close to freezing the  
system will pump warm water into them - loosing some heat from the  
tank but saving the panels.  I think this will work for me because  
freezing is very rare here; many years it will not freeze at all.

I have friends here who have the integral collector storage system  
and they seem to work well here.  But from what you describe I'd be  
more inclined towards something with antifreeze in the panels and a  
heat exchanger.

Good Luck,
Frank

On Jan 22, 2007, at 10:01 AM, Dusch, Jim E wrote:

> Although I realize a superficial question on this is not necessarily
> helpful, I need some opinions on solar hot water systems.  The project
> is intended to preheat domestic hot water and radiant floor water  
> prior
> to sending it through an LP fired Takagi Mobius (which currently does
> all the work).  The project is in Maine, where it gets cold for  
> extended
> periods of time.  What preferences/advice do folks have:
>
> Closed-loop or Open-loop?  Drainback?  Integral Collector Storage?
> Others?
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