You could use a home water heater 120/240V AC thermostat on 12V DC. I just
needs contact with the inner tank. If the water heater has a 120V
thermostat, disconnect all the 120V wires and use it for 12V.
Lee Haefele
"Sailaway" wrote in message
...
"Geoff Schultz" wrote

You can get elements that have both 120V AC and 12V DC feeds. See
http://www.svhotwire.com/divert_loads.html


GBM wrote:
That's great, but:
- how is the water temperature controlled? Temperature should not
exceed
49C to prevent scalding (used to be 60C)
- Once water reaches maximum temperature, what do you do then?

Seems to be of limited value if engine is also used to heat water. Our
hot water gets up to about 45C after an hour of motoring at low speed. It
is self limiting because of engine thermostat.

Just curious because I'm not familiar that with them - do marine water
heaters have any sort of provision whereby you can insert a temperature
sensor, which can then be hooked up to a limiting circuit?