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.......
Doing the Math (WATTS = VOLTS * AMPS)
2400 WATTS = 120 VOLTS * 20 AMP (12 Guage Wire)To my understanding 2400 WATTS is more then the Water Heater can pull
Could someone elaborate on why National Wiring Code would not allow me to use a 12 Guage Wire / 20 Amp Breaker?
Thanks
What do you mean "Much Less Voltage Drop using a #10 opposed to a #12" ?
What would be the side affect for Hooking a #12 Wire pulling 16.7 Amps?
Could someone please explain "Continuous Load" and why a Hot Water Heater falls into this catogory.
Would the Hot Water heater always be pulling the full 2000 Watts or does it only pull 2000 Watts on the highest temp?
I have no problem running #10 Wire but I just ran #12 for a smaller Hot Water Heater and needed to return it because it was too small for its application (Washer/Dryer Room).
Thanks
[snip]
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?
The thicker the conductor, the less its resistance to current, and hence the less the voltage will drop due to the resistance of the conductor -- but #12 wire has a resistance of only two ohms per thousand feet to begin with. To state that #10 wire has "much less voltage drop" in your application overstates the case a bit.
In any event, you need a 25A circuit and hence #10 wire at a minimum anyway, so the difference in voltage drop between #12 and #10 is utterly irrelevant.
Possibly a fire. That's why the Code doesn't permit it.
"Continuous load: a load where the maximum current is expected to continue for three hours or more."
Most of the time, the conditions of use of a water heater would *not* fall into this category, but it certainly could.
The heating element is either on or off.
Well, then, run the #10.
-- 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?
If you are not familiar with the concept of voltage drop, you probably should not be doing your own wiring; it is pretty basic.
Heaters are usually 240v because it wastes less power for a given size of wire.
The main thing is that the wire would get hot, and possibly start a fire. Not likely with such a small overload, but when it happens the insurance company is going to point out that the fire was caused by improper (and presumably uninspected) wiring. I am not a lawyer, but it seems like something best avoided.
The setting affects how long the heater is on. It is always pulling 2000w. It is like your toaster; it is on or it isn't on; darker toast just takes longer.
Good solution would be to get a 240v heater and use the #12 wire. It is good for maybe 3500w, yet will have less voltage drop.
It seems mentally unhealthy to imagine the NEC is based solely on physical reality, vs the interests of wire manufacturers and insurance companies :-) The fusing current for 12 ga wire is 235 amps.
Nick
Well I caved - With a New Born Baby only days away and the reality that Insurance not covering my claim if there was a fire - I splurged the extra money and got 100Ft of 10/2 w Ground Copper Wire.... Strangly enough the Outdoor quality was cheaper then the indoor...... Go Figure
The Wire is run and connected but I have not flipped on the breaker to the Hot Water Heater yet. My plumbing skills have been tested and a small leak has developed on the Treaded Portion of the Hot Water Heater.... Of course I did not let the thread seal cure for 48 Hrs... I am hoping giving it time to seal will do the trick... Anyone have any view on Thread Seal and How long it usually takes to seal the thread?
Thanks you all for the input
This statement is only partially correct. The 80% limitation refers to continuous loads, as defined in the NEC. The Code does not prohibit operating non-continuous loads at 100% of the circuit's rated capacity.
The NEC is based on the desire to avoid fire and electrocution hazards.
Which is, of course, totally irrelevant to the amount of current that can safely be handled by 12ga wire without, for example, igniting its insulation.
-- 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?
You did the right thing
Teflon tape... Only time I ever used pipe dope (if that is what you mean) was on gas, and I don't remember it needing to cure. (At least I didn't do it, and it didn't leak.)
The National Electric Code is written by the NFPA. That stands for the NATIONAL FIRE PROTECTION ASSOCIATION. They write other fire related codes as well. Most of the articles in that code were written because someone died. It is the code so someone does not get hurt or killed.
stretch
I'm guessing you compared the price of 100' of UF to 250' of NM...
If it's leaking, that means you didn't tighten the joint enough. Doesn't matter how long you wait, it isn't going to seal.
-- 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?
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