line voltage thermostat

[Diehard]

100 watts at the lowest temp setting??

It's been so long I really don't remember the details. But it wasn't at minimum setting.
But I wouldn't rely on my figure(Sounds too low). I would call a couple of water heater manufacturers. I'm sure they could tell you.

 

[fixitron]

FWIW, Dayton has a line voltage thermostat rated at 30 amps at 240 vac, with a remote sensor that can be inserted between the tank and tank insulation, controls down to 30 degF. [A 4500 watt element draws just under 19 amps and a 3500 watt element (not as common) draws just under 15 amps.] It lists for about $186. You would have to set up a means where you can switch the control of the heating elements with either the line voltage thermostat or the thermostats that come with the water heater. That can be done by physically changing the wiring each time or by using a DPDT switch, preferably with a center OFF position.
As noted above, that will only protect the tank (assuming no power failure) and not associated piping.

 

[Diehard]

100 watts at the lowest temp setting??

Thinking about this again, the standby heatloss was equivalent to about 100 watt bulb. Even at that, that's 2.4 kWh per day x (say) $0.20/kWh = $0.48/ day x 30 days = 14.40/month. If you're talking a few months a year, that's $43 a year. Hardly worth it! IMHO

 

[TomFOhio]

somewhere....any other comments??

NONE

 

[Diehard]

Another hit and run OP!
He must be busy practicing his soldering.