I am replacing a 30" kitchen range with a new 48". The existing wiring is approximately 30' of romex NM-B 8/3 on a 40 amp breaker. The new range requires as follows:

Maximum connected load: 10.2 kW for
48".
Required power supply: 240V/208V/50A/60Hz for 48".
Minimum supply wire size: L1 and L2 – 8
AWG, neutral – 12 AWG, ground – 10 AWG
For 48".
Total electric rating: 10.2 kW at 240V, 8.8 kW at 208V for
48".
Total amps: 43 amps.



Will the existing wire work for the new range with a new 50 amp breaker? Or do I need to upgrade to 6/3?

Thanks in advance for any input.

You may leave the #8-3 Romex only if you leave the 40 amp breaker.

Of course, you will not be able to use the range to it's fullest capabilities.

To have a 50 amp fully rated circuit, you will need to install the #6-3 Romex.

Now this may confuse the issue, but you may install #8-3 Metal Clad (MC) cable and use the 50 amp circuit breaker.

You can compare the price difference between the #8-3 MC and the #6-3 NM-B.


The reason is that NM-B cable is limited to using the 60 Deg C column of the NEC wire ampacity table #310.16, which is 40 amps. If something other than Romex is used, then #8 wire can use the 75 Deg C column, which is 50 amps max.

Thank you very much. You confirmed what I suspected. Excellent board and resource.

Not only Answered the Question but fully explained why. Extremely helpful to me on my project. Unfortunately, my work network blocks me from leaving a rating.