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  # 1405897 14-Oct-2015 19:06
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Does anyone know if a system exists where the 12 volts from your solar panels can be directly fed into a HW element (is there such a thing as a 12 volt element?) to eliminate storage batteries?

When there was no solar energy available, the normal 230 volt element could kick in to boost the water temp.

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  # 1405898 14-Oct-2015 19:10
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The panels are in a long string making several 100V DC, not 12V. I guess if it was under 240ish then you could directly connect it to the element, but the thermostat wouldnt handle DC so would need something to switch it off and on.

As you are over 32 or 50 or whatever voltage defines extra low voltage, all the panel wiring has to be done by a sparky, no homeowner allowance for solar wiring like we are lucky enough to have in NZ for other home wiring.




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  # 1405908 14-Oct-2015 19:33
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The voltage output of the panels would depend on whether they're wired in series or parallel.

I was thinking (off the top of my head) of some kind of system with a 12 volt output feeding the current directly through an element. I don't know if there's such a thing as a 12 volt DC element.

You'd probably need some electronics thrown in there to regulate it all.

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  # 1405915 14-Oct-2015 19:53
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3kW at 12v is several 100A, so unwise really. There may be some sub 1kW elements made for other purposes that are extra low voltage, but again, needing to switch DC on and off particularly at those currents is not something to really go DIYing.





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  # 1405919 14-Oct-2015 20:00
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  # 1405923 14-Oct-2015 20:03
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You're right, not something to cobble together in your garage. Cock something like that up and you'd likely get a nice fire.

I know enough about electricity and electronics to realise that I couldn't build something like that myself. I was just wondering if such a system could be made to work and if so, could it be cost effective?

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  # 1405941 14-Oct-2015 20:37
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Why would you do that when you are then limiting yourself to powering a single thing off the panels? Put an inverter on it and power anything you like off it. Small added cost to the panels and brackets and installation to make it totally versitile.

Perhaps if you had a need for constant hot water and would always use it then it may make sense, but if you dont use it all, the tank gets hot, turns off and you are wasting all that energy.




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  # 1405992 14-Oct-2015 22:31
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richms: 3kW at 12v is several 100A, so unwise really. There may be some sub 1kW elements made for other purposes that are extra low voltage, but again, needing to switch DC on and off particularly at those currents is not something to really go DIYing.



3Kw @ 12v is 250A, you are looking at some serious cable size, it would be cheaper (and safer) to use an inverter and take it up to 240AC

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  # 1407699 16-Oct-2015 10:52
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When I looked into this a while ago you could get DC HWC elements in NZ.  From memory up to 48v.  Typically lower powered than AC water elements.  But they were not easy to find.






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  # 1407774 16-Oct-2015 11:42
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These guys do them - designed to dump excess off-grid micro hydro power to HWC.
We use this in conjunction with solar water heating in an off grid setup.

http://ecoinnovation.co.nz/c-80-powerspout-plt-accessories.aspx

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