Oven Breaker Size

I noticed the circuit that feeds my double oven is split at a junction box to wire both the oven and a former range top. The wire to the junction box is SER aluminum with a 50amp breaker.
At the junction box the wire is split to two smaller wires (one to the oven, one to the old range top with the wires capped). The wire is brown, solid and unmarked. It looks like 8 gauge.
I'm sure this is not safe. I would like to reduce the breaker size to match the brown wire and remove the unused brown wire from the junction box.
The double oven is marked 120/240 - 7000 watts. I believe that requires a a dbl 40amp.
I just want to verify that I should change the dbl 50amp to a 40amp to match the wire and that 40amp is correct for 120/240@7000watts. I will verify the brown wire is 8 gauge.
Here are a few pictures of the junction box with wires:
http://66.232.129.14/o/oven1.jpg
http://66.232.129.14/o/oven2.jpg
http://66.232.129.14/o/oven3.jpg
Thank you, John
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News wrote:

This is very common and allowed by the electric code. I was going to say it was probably done correctly, but the wirenuts are wrong if the SER is really aluminum -- but it could be tinned copper. If you have aluminum and copper wire spliced together, you need to use a AL7CU or AL9CU rated connector (there's one other rating too, but I don't remember if it's CO/ALR or what.) The aluminum and copper are supposed to be separated by a tin-plated divider that's part of the connector.
Bob
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Thank you for the information. I did not realize that you can reduce the wire size on a circuit and still stay within code.
One more quick question: If the oven is 7000watts at 240v, then it uses about 29 amps. Is that 29amp per leg, or 14.5amp per leg? Thanks again, John
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News wrote:

A built-in oven and a seperate cooktop on the same circuit is a special case.

It is something like 29A on one leg and 29.5A on the other, and 1/2 amp on the neutral (for the oven light.)
If you are sure that the SER is aluminum and not tin-plated copper, you should have the splices redone with proper connectors and deoxidizer goop. (The black and red wires look like they might be done right already.) You might need a large junction box; I can't tell.
Leave the breaker alone; it is OK.
Best regards, Bob
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Thank you very much for your help.
Regards, John
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Bob stated:
> This is very common and allowed by the electric code.
I don't thinks so Bob. Where in the NEC do you find that? The code allows for oversizing a breaker on a circuit running a motor (momentary start-up current draw) but not an oven or range-top...at least not that I am aware. The overcurrent device has to be rated to protect the wire and the equipment. How is a 50 amp breaker going to protect 40 amp wire (assuming its copper)?
Brad in Bend OR
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Brad Behm wrote:

THere is an exception, I think it is commonly referred to as a "tap rule", for wired-in-place cooking appliances fed from a common 50A circuit. (it is very specific.) I'd look it up for you, but I haven't been able to find my code book since I took it to my father's house last summer :-(
The tap wires are relatively short and are protected from overload by the maximum current draw of the appliance. In case of a short, it won't matter whether you have a 40A or a 50A breaker cuz either will trip.
A quick search on google looks like it might be 210.19(A)(3), exception #1, but I can't verify that.
Best regards, Bob
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Well Bob, Hats off to you! The NEC 210.19(A)(3) exception No. 1 says you are absolutely correct! I stand corrected. Thanks I learned something new!
Brad in Bend OR.
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I will

This is Turtle.
Yes Dropping to a 40 amp breaker on # 8-2 with Nake Ground seems to be good here.
Now like ZXCVBob said about the Al. wire in the same wire nut with Cu. wire should have the proper connector to prevent shorts. You might want to do that.
TURTLE
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