I don't think wattage is the independent variable in the equation V*I=Watts. By your reasoning, if the voltage dropped towards zero then the current would rise to an infinite level which is not possible with fixed resistance in the heating coils. Perhaps it might be better to think of the wattage as being calculated from (V*V)/R = Watts. Then if you knew the resistance, you could see the power drawn at different voltage levels and then relate that wattage to the current at each voltage level.
Yes this is correct. Most water heaters are 4500 watts (18 amps), but some are 5600 watts (23 amps). Some are even less than 4500 watts (rare). National electrical code requires #10 wire and a 30 amp breaker. Another issue recently occurring in Texas at least is that the power companies are lowering the voltage causing an appliance to pull more amperage. Watts divided by voltage gives amperage so less voltage gives more amperage. 126/252 volts was once common, but now it is 120/240 volts.
--- In DoIt_Yourself@yahoogroups.com, "petey_racer" <petey_racer@...> wrote:
>
> Because it is Drawing 23 amps and WILL trip a 20A breaker eventually.
>
> The old one may not have been 5500 watts. It may have been 4500 watts.
> No matter, even a 4500 watt unit must be on a (25A or) 30A circuit with at least #10cu wire. Yours MUST be on a 30A.
>
>
>
> --- In DoIt_Yourself@yahoogroups.com, "waspangle" <waspangle@> wrote:
> >
> > Hello learned DIYers,
> >
> > I've got a 6 month-old 80 gal. elec water heater that tripped the double-pole 20 amp breaker. It may have happened twice over a 24 or 48 hour period, the facts are a little unclear here.
> >
> > This unit is rated at 5500/4130 watts, which means it should probably be on a 30 amp circuit. The similar 80 gal heater that this one replaced operated trouble free on this circuit for 7 years. It appears that the wire from the "little gray box" timer to the heater is 10 guage...if it is 12g, replacing with 10 will be no problem. Hopefully a 10g runs from breaker to timer.
> >
> > So, any theories on why it would start tripping this (undersized) breaker now?
> >
> > Many thanks for your input,
> >
> > -Wayne
> >
>
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