Solar hot water, elements in series?

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Solar Mike

Joined: 08/02/2015
Location: New Zealand
Posts: 655
Posted: 04:22am 02 Mar 2020      

Electrically ok, see this Time To Heat Water link, if you only have 900w available and heating 330l by say 30c rise, then will take approx 12 hours.

I'm doing a similar scheme at a rental, except the mains power heats the top element only and its on a timer (not on during the day), lower element connects to 3.6KW PV array and acts as a pre-heater or if enough sun, the top element does nothing when it switches on.

At home I have DIY water heating panels on the roof, if its frosty, a valve on the panel opens and dumps the about to freeze water down the drain, replaced by warmer city supply water; approx 3L lost each occurrence, may do this 10x in a night.