I did measure across the 2 input wires at the upper limit switch on the
water heater (it's a 2 wire system) and did read 120v.

I am pretty sure the wire is 10 guage but I will verify that.

The elements are 3000 watt and read 20 ohms. By my calculation (it's been
awhile but i think I remember) 240 volts across 20 ohms is just under 3000
watts (2880) and since only one is on at a time.....the math works out.

On the side of the heater it does state 240v but I believe this to be a
maximum applied voltage only.

As I said the water is fine once it is heated up but if I do use it up...it
takes much of the day to get it back....estimate 4 to 5 hours. This doesn't
happen very often since there are only 2 people living here most of the
time.

I am not sure if there would be any reason to hook up 120 vice 240. It works
obviously other than the recovery time. Any ideas other than installation
error? It was installed 2 years before we moved in, which was 2 years ago.

So to recap, If I do revert to 240v the wire size must be 10 guage and there
must be 30 amp fuses?

Thanks for all the help and the quick replies.It's piquing my curiosity more
than anything.

Bob

"John Grabowski" wrote in message
. net...
Read the other responses to your question as they provide some good
insight.

If you have 120 volts powering 240 volt elements, it must take several
hours
for you to get warm water. There is a lot of resistance in those elements
and hot water seems unlikely at 120 volts.



"Bob" wrote in message
...
I have an electric water heater (40 Gallon) that is hooked to 120V. 240V
is
run to a shut off switch (fused) just above the heater (3 feet away) but
for
some reason the installer ran 120 to the heater (black and white wires,
the
red is disconnected, and yes I can measure voltage). The main fuse panel
has
2, 15 amp fuses for the circuit.

I was thinking of changing the water heater to 240v for the purpose of
quicker recovery time. Is there a reason the person used only 120V? If I
did
this what would the fuse size in the panel need to be?