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I have a 40 amp breaker for the range receptacle, but the new range specifies a 50 amp circuit.

Can I just have a 50 amp breaker installed or will it require rewiring?

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    I'm afraid I don't know about the wiring. I guess I just need to get an electrician to come and check it out. I have some other stuff that needs work, so it will be what it will be. – user3654185 Dec 6 '17 at 18:17
  • It's good that you're getting an electrician to figure this all out but just to make a quick point in case you were going to deviate from the code. You're better off running the stove on the 40amp breaker if the existing wire is #8 than replacing just the breaker but not the wire. The reason for this is that if you have too much current on the line at least the breaker will trip. While this is annoying it is at least safer than having a 50 amp breaker which wouldn't trip allowing the undersized wire to heat up and potentially start a fire. – Dean MacGregor Dec 6 '17 at 20:16
  • @user3654185 It is no shame to know nothing about wiring. It is shame to know about the lack of knowledge and do the wiring anyway. Your decision is wise. – Crowley Dec 7 '17 at 10:33
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In general, no. Installing a 50A breaker on wiring only designed to support 40A is dangerous and can result in a house fire. 40A circuits need #8 copper wire, whereas 50A circuits need #6 copper.

It's possible, although very unlikely, that the wiring used in the circuit is #6 and thus could support 50A (maybe somebody was planning for the future), but for some reason a 40A breaker was used. The only way to know for sure is to open it up and look at the wiring. The size and other specs should be printed on the sheath; as isherwood mentioned, you're looking for AWG #8 or something similar.

In the more likely case that the existing wiring is #8, you'll either need to pull new #6 wire or get a different (lower-powered) stove that will work with the existing 40A receptacle.

  • There is one possibility of the wire being sized for 50amp that I can think of. When we bought our house the inspector noted that the breaker for our [insert appliance here, I forgot specifically what he referenced] was bigger than the appliance was rated for. If I had jumped to replace the breaker with a smaller one and someone came around behind me they'd find a bigger wire than the breaker needed. – Dean MacGregor Dec 6 '17 at 22:07
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You just have to look

Modern best-practice is to run 6 AWG cable on the stove circuit and then fit a 50A receptacle, which is legal on both 40A and 50A circuits since there is no such thing as a 40A receptacle. Then, once it is known whether the range is 40A or 50A, that correct breaker is fitted.

On the other hand, if it was known the range would be 40A, they may well have fit 8 AWG cable, which is not fit for 50A.

The wire size is written along the edge of the cable jacket, every 12 inches, along with a lot of other useless garf. This can be seen anywhere the cable is visible. On a fully finished house, that may be nowhere. In that case, you'd have to pull the wires out and measure their diameter with a micrometer or other tool.

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Save yourself some money and keep the 40A breaker, as the other answers have mentioned, you're probably looking at rewiring to run a 50A circuit. Worst case, you trip the breaker if you turn on the oven and all burners to high while cooking dinner, but seriously do you ever see yourself doing that?

  • Some ranges have a rather ambiguous spec about this - they are rated for 50A, but there is mention of using on a 40A breaker. It sounds more like lawyer-speak than electrical code, but in general this is not such a bad choice. – Eli Iser Dec 7 '17 at 20:19
  • Thanks to all for the good info. We are closing on the house next week and I'll check the wiring on our walk through the day before. If it is AWG 6, I'll have the 50 amp breakers installed. If it is AWG 8, I'll have it replaced with 6 and install the correct breakers. My wife doesn't take kindly to electrical eccentricities since we had a house with aluminum wiring burn down. – user3654185 Dec 8 '17 at 14:47

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