I've noticed a design change in terms of electric water heater made in
the last 10 years or less.
Prior to that it seems like that the standard heating element wattage
was 3800 per element. Now its 4600 watts per element.
Why the change? Faster recovery times, I suppose...
With 3800 watt elements, a 20 amp 240 v circuit was fine with maximum
current less than 16 amps.
With the 4500 watts elements, a 20 amp 240 v supply circuit is
marginal with a demand current of around 18.75 amps.
I've got a few places that still have electric water heaters on 20 amp
I recently had to replace one during a weekend that was bitterly cold.
The 20 amp breaker kept tripping, as the heater switched from the top
to the lower element. I suspect that the surge current when the
element was cold was enough to trip the breaker.
Working in the bitter cold within a crawlspace to upgrade the circuit
to 30 amps was simply not, for the time being, an option.
I looked in vain for a breaker that weekend with a longer time delay.
Eventually I installed a 25 amp breaker keep the heater on.
YES, YES, I know, with a 20 amp circuit, on 12 gauge wire, that 25 amp
breaker is a code violation. You don't have to give me flack for
that...However, I'm not worried since it's only a temp solution and
there is no constant demand current over 18.75 amps. Also, an element
short will trip that 25 amp breaker almost as fast as a 20 amp one. In
the spring I'll put in a 30 amp circuit.
I'd never seen 25 amp 240 volt breakers until recently. There must be
a demand for them..
Anyone else have this problem?