Solar Water Pump?

[boatboy63]

I plan to build a dhw preheater to help cut my electric bill in the summer. Seems I remember seeing a post from several members on the site who are using solar powered water/circulator pumps. I have searched, but can't find the thread. This would work perfectly to circulate water from a roof coil to a storage tank. If anyone can give any advice or source on where to find these, I would appreciate it. TIA

 

[kenny chaos]

Here; http://www.google.com/search?source..._enUS347US347&q=solar+powered+circulator+pump

 

[peakbagger]

I have a solar powered circulation pump on my solar hot water system. It has been running for three years with no issues. The original system came with a 20 watt PV panel that was inadequate to the run the pump up in northern NH. I switched to a 40 watt panel and it works 12 months per year. The other modification was the installation of a DC pump controller that makes sure that the pump runs only when the fluid in the panel is hotter than the water in the hot water tank.

One source of pumps is

http://www.altestore.com/store/Solar-Water-Pumps/Circulating-Pumps/c490/

Here is a link to the 12 volt controller (runs off the same PV as the pump)

http://www.arttecsolar.com/specs.htm

 

[Dune]

What about gravity circulation? From what I understand, the main thing is to significantly oversize the piping.

 

[boatboy63]

Thanks for the replies. I was wanting to find out what some of you guys use and what is preferred. Seems like I remember someone posting about a solar pump that was less than $100 and several people had purchased them and said they did a great job. Solar powered would be perfect, as circulation would not be necessary at night as the water wouldn't be heated from the sun then. I want to mount the storage tank in the attic area because of the added heat up there in the summer and the 120+ degrees it typically stays, should be a boost also. Thermal siphon will not work because the tank will be lower. A gravity tank wouldn't work either due to this being plumbed into my electric water tank and constantly having full water pressure on it. I plan to put a couple of valves on my existing water heater, take what is now the inlet (cold) water supply going to the heater, run it to rooftop coils and storage tank, then take the water coming from the tank and use as inlet (cold) water side of heater. This should cut probably 75% or more of my electric usage for water heating in summer. In winter, my upcoming install of a gasification type OWB will provide all my dhw.