water heater replacement

[kwired]

I have a code book as well. :thumbsup:





4500 watts = 18.75amps or 12.8 ohms

12.8 ohms at 208 volts is 3380 watts or 16.25amps

16.25 x 125%= 20.3125

next size up, 25 amps

150% of 16.25= 24.375


One could argue there is no listing at 208 volts, however some heater do have a 208 volt listing.


Yes I doubt the inspector would care or catch it, most do not and 30 is common at that voltage and wattage, but technically the code would require 25amps if followed to the letter.

I was going to look up information you quoted and comment on it, I knew there was a maximum but wasn't sure what it was - apparently 150%. So if a 240 volt supply then 1.50 x 18.75 amps is 28.13. Can go next standard size device higher - that is probably the main reason you see most 4500 watt water heaters on a 30 amp breaker even though they can also be on a 25. Many not know this is why, they just purchase the 30 because they are often easier to come by then a 25, but if we were supposed to use the 25 they may be a little more common.

Would you agree or disagree that the 30a breaker would do so better than the 40a breaker would?

Ignoring the fact that 30 amp is the max per what I just mentioned above, IMO all it really does is provide ground fault protection, and I don't think what little additional protection would be offered really makes much difference as the instantaneous trip level is still probably significant enough protection even up to a 60 amp breaker.

Overoad protection is basically pointless here, how do you overload a circuit with a fixed resistive load? Fault to ground if somehow developed in the mid section of the element would draw less current then normal operating current. Fault near termination of element draws near same current as direct line to ground fault and instantaneous trip function clears that condition.