Electrical Circuit Larger Than Needed

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Greenthumb77

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I am planing a kitchen remodel and my wife wants a Bosch single wall oven, undercounter installation. The instructions say a 30 A breaker 240/208V. I checked the panel and the circuit has two 40 amp breakers to serve the existing wall oven.

We would like to replace the exiting cooktop with a Bosch induction that requires a 30 amp breaker 240/208 V. The existing circuit that services the old cooktop has two 40 amp breakers.

Here is my question. Can i use the existing circuits that are 40 amps for the new appliances that need 30 amps?

Thank you for your advice

Jim
 

Texas Wellman

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Please note that I'm not an electrician. That being said the breaker protects the wire as much as the appliance. You can always downgrade the existing breaker to a two pole 30 amp and use the same wire.
 

Jadnashua

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Yes. The CB is there to protect the wiring up to the device. If you really wanted to, it would be legal to install a smaller breaker in the panel, but it is not required. You can use wire larger than necessary for any protection device (within reason...the wire must still fit the attachment point), but you can never use a bigger breaker with a smaller wire than required. Think of it like this: you may have a 15A circuit in your living room, and only plug in a 60W (~0.5A) lamp...things work fine. Generally (there may be exceptions), a CB on a circuit is sized for the wiring, but more importantly so that the wiring in the wall doesn't overheat and cause a fire. A short in the device will cause a 40A breaker to trip about the same time as a 30A breaker.
 

Cacher_Chick

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What should be confirmed is the actual wire size that is installed. Don't make the mistake of assuming anything.
 

Onokai

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That wire size for your existing 40 amp breakers should say #8 on it?.

If that's a yes just wire them up with 30 amp breakers.
 
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JWelectric

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The appliance calls for a 30 so a 30 must be used, nothing bigger. As some has said just change the breaker to a 30 and move on
 

Speedy Petey

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I am planing a kitchen remodel and my wife wants a Bosch single wall oven, undercounter installation. The instructions say a 30 A breaker 240/208V. I checked the panel and the circuit has two 40 amp breakers to serve the existing wall oven.

We would like to replace the exiting cooktop with a Bosch induction that requires a 30 amp breaker 240/208 V. The existing circuit that services the old cooktop has two 40 amp breakers.

Here is my question. Can i use the existing circuits that are 40 amps for the new appliances that need 30 amps?

Thank you for your advice

Jim
Even if you could, WHY would you bother???
I agree with JW, Just change the breaker.
 

Jadnashua

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You need to read the installation instructions, there's a difference between it saying you need at least a 30A breaker, and one that says you require a 30A breaker. Regardless, though, you can never use a bigger breaker than the wiring supports, but can use a smaller one (as long as the wire will fit into its terminals).
 

WorthFlorida

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If your kitchen remodel requires a permit, you'll definitely need to upgrade the electrical. For one, all counter tops outlets must be 12 gauge wire, 20 amp breaker and you must have TWO circuits. I do not have my NEC book with me to give you the section number. It is also a good time to run a separate circuits for the refrigerator, microwave, dishwasher and disposal if it is not already wired that way. NEC code dos not require a separate breaker for the refrigerator but you do not want a toaster tripping the breaker with the refrigerator and not know it.

If you new stove states a 30 amp breaker then it must be a 30 amp but you need to read the installation manual. Some internal wiring of the stove may not be designed to handle a 40 amp load and do not forget that most new stoves have electronics that need protection.
 

WorthFlorida

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... I checked the panel and the circuit has two 40 amp breakers to serve the existing wall oven....he existing circuit that services the old cooktop has two 40 amp breakers.Jim

You have two 40 amp breakers, not four. These are 220v circuits. A 40 amp 220v breaker is actually two 20 amp breakers tie together with a pin.
 

Reach4

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You have two 40 amp breakers, not four. These are 220v circuits. A 40 amp 220v breaker is actually two 20 amp breakers tie together with a pin.

A 40 amp 220v breaker is actually two 4o amp breakers tied together with a pin.
 
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