Any Pro electrians on here?

[icicle]

I have a rant about electrians in general so I'm Sorry to the pro's that really understand where I'm coming from.

Here is my small rant.

Last month while I was installing my hot water heater I had a simple question about wire size for my hot water heater.

I have a small 40 gal, 220 ac volt 3800 watts water heater and the wires coming out of it is 12/3. I called three different places and they all said I need 10/3 wire, which seems a little more than I needed and I thought that the old rule of thumb was if a wire was 12/3 your not supposed to run the next size up makes logic.

So I went digging though a box and found my little pocket referance book.

well I just had to look up the wire size and for 12 gauge wire it will hold 20 amps.

and if my math is right 3800 watts/220 v. Ac = 17.2727 amps. and again if my math is corect: 17.2727 amps / 20 amps = 0.863635 amp useage

And when I called one of the places back to question them one of the guy finaly ask me what size I was using and told him 3800 watts. and he finaly ask someone else if 12/3 wire was ok, then he said yes it was fine.

So why in gods green earth do they want me to use 10/3 wire rated for 30 amps.

Do they want me to burn up my hot water heater from the inside out for running too heavy of wire.

The National Electrical Code [NEC] requires their own cable sizing for premises wiring. Refer to the NEC rules to determine building wiring, as this page relates to electronic equipment wiring. For reference, the ampacity of copper wire at 300C for common wire sizes

14. AWG may carry a maximum of 20 Amps in free air, or 15 Amps as part of a 3 conductor cable.
    
12. AWG may carry a maximum of 25 Amps in free air, or 20 Amps as part of a 3 conductor cable.
    
10. AWG may carry a maximum of 40 Amps in free air, or 30 Amps as part of a 3 conductor cable.
    
8. AWG may carry a maximum of 70 Amps in free air, or 50 Amps as part of a 3 conductor cable.
   
   

Sorry if this is in the wrong spot.



Whats the point?

[spinningmagnets]

I am still learning, and I clearly know less than you already do. While you are waiting for an answer, could you answer a question for me?

I have learned from this forum (and also the electric bike forums) that if you go to a higher voltage, you can get the same Watts from lower amps.

This allows you to use thinner (less expensive) wire without fear of the wire overheating.

I would have thought ONLY the resistive heating element inside the water heater would get hot. If the power supply wire was thicker than neccessary, it may have been a waste of money, but would not have caused problems by allowing too much flow to the elements?

"...Do they want me to burn up my hot water heater from the inside out for running too heavy of wire..."

If I misunderstand this, I apologize, and I merely want to learn. Thanks in advance!