In article , "Burhans" wrote:
All,
I recently purchased a 20 Gallon Hot Water Heater (120V) 2000 Total
Watts...... The National Wiring Code stated that it needs a 25 Amp/10 Gauge
Wire.......
[snip]

Could someone elaborate on why National Wiring Code would not allow me to
use a 12 Guage Wire / 20 Amp Breaker?

Because a water heater is a "continuous load" as defined by the Code, and
continuous loads are not permitted to exceed 80% of the rated ampacity of the
circuit. For a 20A circuit, that is a maximum continuous load of 16A. Your
water heater will pull 2000W / 120V = 16.67A, which is 83.3% of the ampacity
of a 20A circuit. Thus you need at minimum 25A and 10ga wire. But don't knock
yourself out trying to find a 25A breaker - you can run 30A on 10ga wire, too,
and it will be much easier to find a 20A breaker.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?