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
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:
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.
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?
A built-in oven and a seperate cooktop on the same circuit is a special
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.
> 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
Brad in Bend OR
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
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.
This is Turtle.
Yes Dropping to a 40 amp breaker on # 8-2 with Nake Ground seems to be good
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.
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