Replacing 30 circuit w/40 amp

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  #1  
Old 05-15-11, 11:07 AM
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Replacing 30 circuit w/40 amp

Hello all,

We're planning on upgrading our cooktop to an induction cooktop and need to upgrade the current 220-30 amp circuit to a 40 amp circuit. Is this as simple (or difficult) as replacing the current 10/3 wire with 8/3 gauge from the breaker box to the range and replacing the breaker or is there something I'm missing? The cooktop is about 30 feet from the breaker box.

I've run new 110v circuits many times, but not 220v.

Thanks,

Bob
Garland, TX
 
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Old 05-15-11, 11:29 AM
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Yes, it is that simple to run a 120/240v circuit. Since this is a cooktop it may be 240v only. In that's case you could run 8-2 w/g instead of 8-3 w/g. Of course 8-3 might be useful if you ever upgrade to a 120/240v cooktop or decide to install a range.
 
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Old 05-16-11, 10:40 AM
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Are you sure the induction cooker only needs 40A? Those are only of the few types of high-end ranges that occasionally require 50A and #6-3/g cable.

Yes, the basic method of running the cable is the same. You need cables clamps on the boxes, staples to support the cable, run along framing members to protect it. The cable does not need to be stapled where it is fished through a finished wall. Unlike normal 120V circuits, the #8 cable is heavy enough that you do not need to run it through bored holes in the framing. It can be stapled directly to the underside of flooring joists as long as it is otherwise away from harm. If you go through an attic you still need to run alongside a 2x4 for protection from footsteps.
 
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Old 05-16-11, 07:14 PM
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He said a cooktop, not a range. 40A seems right.
 
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Old 05-16-11, 07:19 PM
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We're planning on upgrading our cooktop to an induction cooktop and need to upgrade the current 220-30 amp circuit to a 40 amp circuit.
Have you checked the installation manual for the proper amperage and voltage/voltages required for the new cooktop?
 
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Old 05-17-11, 06:28 AM
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Thanks for the responses.

We haven't purchased the cooktop yet, but in looking online, all of the 30" induction ones I've seen show 40 amps. The 36" cooktops may be more. I'll wait until it's purchased before actually running the cable.

The cable has a 8' run between floors, but since I have to pull the cabinet above it for modifications for a microwave, I should have plenty of access, especially if I use the old cable to pull the new one through.
 
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Old 05-17-11, 07:57 AM
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Originally Posted by bob.w View Post
I should have plenty of access, especially if I use the old cable to pull the new one through.
The old cable likely will be fastened with staples unless it was fished.
 
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Old 05-17-11, 09:26 AM
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Originally Posted by bob.w View Post
since I have to pull the cabinet above it for modifications for a microwave
Based on current code the microwave will probably require a dedicated 120V 20A circuit too, in case one isn't there already or you weren't already planning for that.
 
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Old 05-17-11, 05:50 PM
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I plan on pulling a 12/2 20a circuit for the microwave at the same time. Since all the spots in the panel are full, I'll have to switch one of the current 20a breakers out for a tandum 20a breaker (Sq.D QO box).

I'm hoping the current wire won't be stapled between the floors, but if it is, I'll just have to leave it and snake a new one. I've done it before to about the same area in the kitchen for a ceiling fan, so hopefully it won't be a problem. If it is, I'll be back for snaking tips.

Thanks for all the help.
 
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Old 05-17-11, 07:17 PM
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all of the 30" induction ones I've seen show 40 amps. The 36" cooktops may be more. I'll wait until it's purchased before actually running the cable.
And......what is required voltage? It could be 240 volt or it could be 120/240 volt. If you have the model number you can look up the information online.
 
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Old 05-17-11, 08:12 PM
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Replace the breaker for the MW with one on a circut not requiring AFCI protection.
 
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Old 05-17-11, 09:08 PM
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Originally Posted by Justin Smith View Post
Replace the breaker for the MW with one on a circut not requiring AFCI protection.
If it is dedicated and in the kitchen that would be an NA statement about the MW receptacle.
 
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Old 05-18-11, 12:09 PM
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Kenmore #4380
Voltage: 220/240V
Total Connected Load: 7.4 kW @ 240V / 6.7 kW @ 208V

So I'm assuming a 8/2 w ground and a 40A double breaker is all that's needed for the cooktop...is that correct?

Actually, since it would only be about another $20 for 8/3, I'm considering it. That way I'd be set if we upgrade the cooktop again in another 10-15 years or decide we don't like the induction stuff.
 
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Old 05-18-11, 12:45 PM
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Originally Posted by bob.w View Post
So I'm assuming a 8/2 w ground and a 40A double breaker is all that's needed for the cooktop...is that correct?
Correct.

Actually, since it would only be about another $20 for 8/3, I'm considering it.
A very good plan.
 
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