50 Amp breakers

[Al D. Bolt]

It seems that using #8 wire for 50 Amp breakers is a common practice when so many electrical charts say #6 wire should be used. Any rule of thumb pointers out there for the inspection or report? Thanks.

[Christopher Currins]

you can use #8-3 MC cable with a 50 amp breaker, but not #8 romex, nonmetallic

[Robert Meier]

It also depends on the application. #8 on a 50 amp feeding an HVAC unit or a motor would likely be code compliant.

Although their conductors are rated for 90° C, for NM cable, SE cable, or AC cable embedded in insulation, you must use the 60° C column of NEC Table 310.16 to find their ampacity. The requirements for interior SE cable installations in Article 338 send you over to Article 334 (NM cable) to determine their ampacity.

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor.

320.80 Ampacity.
The ampacity shall be determined by 310.15.
(A) Thermal Insulation. Armored cable installed in thermal insulation shall have conductors rated at 90°C (194°F). The ampacity of cable installed in these applications shall be that of 60°C (140°F) conductors. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor.

II. Installation
338.10 Uses Permitted.
(A) Service-Entrance Conductors. Service-entrance cable shall be permitted to be used as service-entrance conductors and shall be installed in accordance with 230.6, 230.7, and Parts II, III, and IV of Article 230.
(B) Branch Circuits or Feeders.
(a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334.
FPN: See 310.10 for temperature limitation of conductors.

[Al D. Bolt]

So, in regards to a home inspection report, what should be stated (if anything) when there is a 50 amp breaker with #8 wire for a range? AC?

[Joe Farsetta]

Do NOT quote the NEC. It is NOT a code violation unless and until the AHJ has determined it to be so.

I would write it up something like this:

Inspector observed #8 electrical conductor connected to a 50-ampere circuit breaker. It is possible that the current wiring configuration is not properly suited for the application, and further investigation/evaluation by a licensed electrical contractor is recommended, to ensure that the installation is proper and conforms to all applicable electrical codes and requirements.

[Robert Meier]

Originally Posted by abolt

So, in regards to a home inspection report, what should be stated (if anything) when there is a 50 amp breaker with #8 wire for a range? AC?

I'm not an HI so I will defer to Joe's advice. However, for an AC unit the conductor size does not have to match the circuit breaker size. You would need to know the Minimum Circuit Ampacity (MCA) of the unit and the Maximum CB or Fuse size. This information is listed on the nameplate of the unit. The conductors are sized according to the MCA and they can be protected by any size OCPD from the MCA up to the maximum. Take a look at the example nameplate below. [MCA 23.3 amps, Max fuse or CB 30 amps]. It would be permissible to have #12 conductors protected by a 30 amp CB or fuse.