Looked closer -- the water heater is on a 20 amp circuit! Man, that's dinky.
I'll have to dig up the specs on the heater or take of the insulation and check out what it's supposed to be installed on, but given that in the winter the circuit will sometimes go a month without breaking (if it lucks through the laundry cycle), I'm guessing it's actually rated at 20 amps.
I wonder, though, if it's not tripping during low fluctuations of voltage coming off the grid? W = VA, volts go down, amps go up, breaker trips?
Damn it, though, looks like I'll have to have someone put in a new breaker box before modernizing the water heater...
I hope you're in hot water, Patiodog, of the good kind.
20 amps isn't dinky, if the load matches the circuit rating.
Near as I can figure, and I may well be wrong, but I think that the H2O heater elements were too large for the 20 amp/[12 gauge wire ?? circuit]
20Amp x 240 volt = 4800 watts x 0.8 = 3840 watts
30Amp x 240 volt = 7200 watts x 0.8 = 5760 watts
My guess, and it's only a guess. In winter, with the cooler temps, the 20 amp circuit was better able to carry the "overload".
When more load was put on it ---> more laundry being done ---> more hot H2O required ---> longer H2o heater run times ---> more chance for an overload and then the breaker pops.
High humidity --> higher ambient temps --> circuit wire heats up more --> more chance for a breaker tripping.
I hope you replaced the 20 amp breaker with a 20 amp breaker.