"Bob" wrote in message
...
When I say "only one is on at a time" , I mean only one element in an
electric water heater is on at any given time. This I am sure of.

The label states "maximum allowable rating" and states "240V" with 2 "3000
watt elements factory installed"

And I agree..it will heat up alot faster (4 times faster) with 240v vice
120v but is the only reason it would be hooked up to 120v is that the
installer didn't have a clue?

For this water heater it will draw 12.5A at 240V so you only require a 20A
circuit. The smallest element I've ever heard of in a 240V model was 3600W,
but even that will fit on a 20A circuit. I have a 5500W model, and that
requires a 30A circuit. Water heater circuits must have an ampacity of 125%
of the nameplate amp rating. If you have wires for a 30A circuit (i.e. 10ga
copper), you can porbably install any replacement residential heater that
you want. A 20A circuit will limit you to the ones with smaller elements.

The only reason I can think of someone would have done this was to "save
energy". However, you will end up using the same amount of electricity to
heat the tank back up. You only save when cold water starts coming out of
the shower so you have to get out. Perhaps the previous owner had a person
who liked to take forever hot showers and got tired of paying for it.
Although a properly wired 20 gallon model would probably cure that too and
allow another shower in 15 minutes.

--
Mark
Kent, WA