Solar hot water, elements in series?

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Joined: 05/06/2004
Location: Australia
Posts: 4808
Posted: 02:57am 02 Mar 2020      

I currently use a 330 litre hot water tank and a couple of thermal solar panels for my hot water. Its got a controller and a 12v circulation pump. The plumbing is leaking, and in winter I need to cover the panels to stop them freezing, its a bit of a crude setup.

I was thinking of just heating the water with my existing off grid power, using 230vac and a timer so its only heating during the day, plus the tanks own thermostat.

Problem is my inverter is only good for 3kw to 4kW continuous, so if I'm running the air conditioner, and flick on the kettle, I really only have a 1000 watts to spare before the inverter starts beeping and shuts down.

I cant find a source of 230vac hot water elements under 1000watts. This hot water tank does have two elements, one near the top and another near the bottom. If I fit 2 1800 watt elements, wired in series, that should be 900 watts.

I'm guessing this would take 4 to 5 hours hours to heat up the tank, which should be OK. Plus the hottest water will be near the top outlet, and I'm living alone so dont need that much hot water.

Thoughts? Are there any issues with running elements in series?
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