Call us soft....or getting old, but when at anchor at the beginning and end of the sailing season here in the Mediterranean when temperatures are cooler than in the summer months we don't want a cold water shower at the end of the day. We prefer not to start the main engine (glazed bores, additional engine hours, noise, diesel fuel), or our portable generator (noise, petrol) to warm the water so we decided to install a "Dual Coil Water Heater" from Surecal Surecal-twin-immersion-heater into our calorifier (hot water tank) earlier this year. It was a pretty straightforward job of unscrewing the old immersion element and replacing it with the new one.

twin coil immersion heater installed

From a wiring perspective it was also pretty straightforward.

The 12v circuit was connected through a 12v/70Amp relay adjacent to the calorifier and via our "Victron Battery Monitor" Victron bmv-712

12v & 240v wiring

The Victron battery monitor has a configurable relay built in so we can configure it to switch on and off under various conditions. Currently its configured to use the "High Voltage Relay" facility. It comes on when the battery voltage exceeds 13.6v and off again at 12.7v.

victron battery monitor relay wiring

The 240v circuit which was already in place for the old element so just needed reconnecting.

wiring - 240v left, 12v right with relay

So how effective is it?

Well it's fair to say that we're extremely pleased and we've had hot water every day since leaving the marina. Typically our batteries are fully charged by our solar array by around 11:00 and at this point instead of just dumping the excess current, it is directed to the water heater. Within a couple of hours the water is piping hot and the built in thermostat then takes over switching on and off as necessary to maintain the 65°c. A perfect "green" solution in our opinion and two very happy crew.