Why complicate things? This seems to imply that you will be leaving the inverter function ON all the time, right? Or else the relay wouldn't work. If you are intending to do this when you are away from the boat, then shorepower would either be available, making it moot, or you'd be disconnected from shorepower and want to dump the wind power, but there'd be no need for hot water 'cuz you wouldn't be there.
If you are on board, then it's simpler to simply turn on the heater when your conditions are met.
How are you controlling the inverter function of the Freedom? Link 2000? Remote panel?
The heater element only usually needs about 15 minutes or so to warm up 6 gallons. If you have an 11 gallon heater, maybe half an hour. We never leave ours on beyond that time, and only turn it on again when the hot water runs out when power is available. I've used our Freedom 15 inverter function to run the heater element, but only with the engine running. Only done this twice, since we change our showering and hot water habits to only after engine running, thus negating the need for electricity for hot water. Too many people leave their hot water heaters plugged in all the time.
What you'll find is that you'll draw down the voltage of the house bank so much by using the inverter function to heat the water that I'd bet the relay would start chattering, at best, or only open for such a short period of time as to make the automatic feature somewhat useless.
I would recommend a manual operation. I'd also try it out manually first to see what happens and to see if I'm anywhere close in my evaluation.
Interesting concept though.
Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
Last edited by Stu Jackson; 10-20-2010 at 01:57 PM.