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Forum Index : Solar : Solar Hot Water
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VK6MRG Guru  Joined: 08/06/2011 Location: AustraliaPosts: 347 |
Hello everyone. Firstly, hoping that everyone had a Merry Christmas and that you all have a fantastic and safe New Year! I've been following Chris from Justin Case YouTube channel and he has been showing off a product that he is trialing that is a MPPT controller for a standard electric hot water service. Product website here . YouTube link here . Just found the price of the product and it's not cheap! But I think it will work well for my place.... Just need to save up for it! Regards, Matthew VK6MRG & VK3MGR Its easier to ask forgiveness than to seek permission! ............VK6MRG.............VK3MGR............ |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I think this is the original solar hybrid hot water booster I'm confused, no wait... maybe I'm not... |
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| VK6MRG Guru Joined: 08/06/2011 Location: AustraliaPosts: 347 |
Hi Yahoo2, WOW, big difference in price! Would be good to get one to test. Regards, Matthew VK6MRG & VK3MGR Its easier to ask forgiveness than to seek permission! ............VK6MRG.............VK3MGR............ |
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Tim_the_bloke Senior Member  Joined: 15/11/2009 Location: AustraliaPosts: 105 |
Interesting. I hope more such products will soon appear on the Australian market. Today (01-01-2017) is the first day thousands of households in NSW lose their solar feed in tariff subsidy, meaning a likely 90% drop in price the electricity sold to the grid from roof top solar panels. So, there is now a real market for such gadgets. Presumably this gadget feeds DC into the water tank heater element. I note this gadget uses the hot water tank's existing mechanical thermostat. I wonder what happens to such a thermostat switching off DC current. Will there be a flash each time it switches off? |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Only the first couple times if it even survives the first switch off. Those thermostats are not capable of switching high current DC, first time it turns off under load will be like striking an arc with a welder. A couple MOSFETs controlled by the thermostat would be a far better solution. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| VK6MRG Guru Joined: 08/06/2011 Location: AustraliaPosts: 347 |
Hi Tim, From what I have read the unit puts out modified square wave so like an old school inverter output not straight DC. Regards, Matthew VK6MRG & VK3MGR Its easier to ask forgiveness than to seek permission! ............VK6MRG.............VK3MGR............ |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If you already have grid tie solar the only hardware you need is a timer to turn on the power to the hot water system during the middle of the day when there is sufficient solar power. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Tim_the_bloke Senior Member Joined: 15/11/2009 Location: AustraliaPosts: 105 |
Where in the circuit would you put the timer? 1: Divert the inveter output to the hot water tank? Would not disconnecting the inverter from the grid stop it working? Perhaps leave the inverter grid connected but use the power before the feed in meter. Would this cause problems? Why have a timer? 2: Between the main supply and the hot water tank's secondary element? This would bypass the off peak switch without interfering with it. Mmm, as I type I reckon option 2 would work well for tanks with multiple elements. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Just connect it to your AC mains and set the timer to work in the hours where there is sufficient sun. If you have off peak you could use a contactor to disconnect that and connect to the same circuit as your Inverter is on. No need to disconnect the Inverter from the grid, when the hot water is up to temperature it will turn off and all excess power will go back to the grid. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
Gday Maddness, we are useing the timer switch that you decribe ,it works well, we just set it to come on during middle of the day for a hour or two, when theres max solar output. This time of year(summer) the hotwater cylinder and timer are switched off because our solar water is doing the heating. Fred |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If the water is hot enough the thermostat should be off so anyway. My charge controllers on my off grid solar has a function called waste not which controls a solid state relay to connect AC power from the inverter. Instead of reducing power as the batteries get to the absorb voltage it diverts the excess power to the solar hot water system. However with plenty of sun the thermostat is usually off by the time the batteries reach absorption and therefore no power is used by the hot water heater. When we build a new house shortly I am wondering if I will even bother with solar hot water panels and just run it all from solar PV with a coil on the back of a wood heater as a booster in very cloudy weather. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
Yea that sounds like a good system. The one thing we don't have is a wetback on our fire, they are brilliant, I was thinking of adding one next year. The fire is nearly 10 meters from the cylinder,but its below the cylinder so with insulation on the pipes it should work fine. |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
You can always add a circulation pump if needed, I have built my own controller using and Arduino for my solar HW. It would work just as well on your fire if needed. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| flc1 Senior Member Joined: 20/11/2011 Location: New ZealandPosts: 242 |
yep, good idea,thanks |
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