Hello, I have a question regarding 12-2 NM cable sold for residential wiring. The specification says that 12 gauge wire is for 9.3 A maximum power transmission and 41.1 A for chassis power. The copper wires in the cable are bundled, therefore, according to the specs, the maximum current should not exceed 9.3 A. An electric kettle alone takes about 1.5 kW, which translates into roughly 12 A current.

Why is then this cable required by code for wiring kitchen outlets and for kitchen circuits with 20 A breakers?

Or does this mean that this cable is acceptable in 20 A kitchen circuits as long as a thicker gauge is pulled through the house to deliver power from the main board to kitchen?

Thanks, h.

Don't know where you are getting those numbers. 12/3 NMC is rated for 20 Amps. Standard kitchen wiring is 2 X 20 Amp circuits, GFCI protected.

Don't know where you are getting those numbers. 12/3 NMC is rated for 20 Amps. Standard kitchen wiring is 2 X 20 Amp circuits, GFCI protected.

This info is in technical wire gauge tables. This is why the whole business is confusing. Cables are bundled insulated wires with little possibility for heat dissipation. In old houses with original wiring, "hot" and "neutral" 12 gauge wires are pulled separately from the main meeting only at receptacles etc. This makes them individual chassis with a much higher current rating.

Should the feed wire for 20 A kitchen circuits be at least 10 gauge?

This info is in technical wire gauge tables. This is why the whole business is confusing. Cables are bundled insulated wires with little possibility for heat dissipation. In old houses with original wiring, "hot" and "neutral" 12 gauge wires are pulled separately from the main meeting only at receptacles etc. This makes them individual chassis with a much higher current rating.

Should the feed wire for 20 A kitchen circuits be at least 10 gauge?What technical wire gauge table are you referring to? The only ones you need are in the NEC.
Yes, it can be confusing, which is why DIYers should not put such little importance on things like residential wiring. The whole "it's not rocket science" thing is BS. No, it's not rocket science, but it's not that simple either.

In some old houses knob & tube wiring was used, but not many.

No, #12 is breakerd at 20A. In fact, the actual amperage is much higher, but we are limited to 20A.

Why are you asking all this? What are you questioning and why?

What technical wire gauge table are you referring to?? The only ones you need are in the NEC.
Yes, it can be confusing, which is why DIYers should not put such little importance on things like residential wiring. The whole "it's not rocket science" thing is BS. No, it's not rocket science, but it's not that simple either.

In some old houses knob & tube wiring was used, but not many.

No, #12 is breakerd at 20A. In fact, the actual amperage is much higher, but we are limited to 20A.

Why are you asking all this? What are you questioning and why?

Thanks for all the info. I am trying to make an estimate for materials and see if any extra circuits are necessary and what kind for a kitchen in an old house with limited amperage and number of circuits.

Yes, it is confusing because different agencies provide different information, but not because it is so difficult, so it should be left to professionals.

The one I have pulled the specs off is American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies and wire strength (http://www.powerstream.com/WireSize.htm)

Stick with residential building wiring charts. I would not bother with electronics or industrial type sites and charts.

Also, it is not as simple as "what does the chart say?" The NEC says #12THHN has an ampacity of 30A, but there are several other sections that limit it to 20A in NM cable in most installations. The chart is not always the bottom line.

The same #12NM cable for an air conditioner condenser could very well be on a 40A breaker and still be safe and completely within code.

Where are you located?


Or does this mean that this cable is acceptable in 20 A kitchen circuits as long as a thicker gauge is pulled through the house to deliver power from the main board to kitchen?

That statement makes me think that you are possible in UK or EU.