Oven/Cooktop Wiring

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Old 03-28-06, 08:48 AM
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Oven/Cooktop Wiring

Hi everyone, I have a standard oven with a 4 prong receptacle and 50 amp breaker. I am replacing it with a built-in oven and separate cooktop. I was planning to just run another circuit and add another 4 prong receptacle and 50 amp breaker so I will have a circuit for each of the appliances. I have a few questions for anyone who might have experience with this.

Does the new circuit need a 50 amp breaker like the first, or does it depend on the requirements of the cooktop?

What wire should I use, I saw there are different sizes depending on the amperage?

Should the existing breaker remain 50 amps?

I have some experience with wiring but I have never dealt with 220 before so any help would be greatly appreciated!!
 
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Old 03-28-06, 10:24 AM
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Originally Posted by floridagator
Does the new circuit need a 50 amp breaker like the first, or does it depend on the requirements of the cooktop?
Depends on the cooktop, but probably more like 30A. You need to get the installation instructions from the manufacturer. You need to know the amperage and whether or not the cooktop uses pure 240V or 120/240V. If you have a link to the manufactures website and a model number we can probably help you decipher the specs.

What wire should I use, I saw there are different sizes depending on the amperage?
Depends on #1.

Should the existing breaker remain 50 amps?
Depends on #1, but probably not.
 
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Old 03-28-06, 10:26 AM
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Post was duplicate of Bens.....deleted
 
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Old 03-28-06, 11:03 AM
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One thing to note, when you use the old branch circuit for the new appliance: If it calls for a 30 amp circuit, get the 30 amp breaker. There's no crime at all in having an absurdly large wire compared to the breaker it's connected to.

By code, you'll also need to get locks for your circuit breakers, unless you install a disconnect next to the appliance. (That way, the proverbial serviceman can lock out the appliance while it's being worked on.) As it sits right now, to disconnect your range all you do is pull the bottom drawer out and yank the cord, right? Well, with the fancy upgrade, there will be no cord to pull.

Be sure to pull a three-wire plus ground (red, black, white & bare) for the new 240V appliances, and be sure to remove the neutral-ground jumper from the whip on the new appliance. That way, neutral current is flowing only on the neutral, as it should be.
 
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Old 03-28-06, 11:18 AM
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By code, you'll also need to get locks for your circuit breakers, unless you install a disconnect next to the appliance.
Can you give the code reference?

Be sure to pull a three-wire plus ground (red, black, white & bare) for the new 240V appliances, and be sure to remove the neutral-ground jumper from the whip on the new appliance. That way, neutral current is flowing only on the neutral, as it should be
Don't we need the voltage requirements before we can determine if a neutral is required?
 
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Old 03-28-06, 11:28 AM
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Product Info

Thanks for being so helpful. Here are the appliances which have links to the owner manual information:

Oven
http://www.frigidaire.com/products/c...PLEB30S9DC.asp
Cooktop
http://www.frigidaire.com/products/c...PLEC30S9EC.asp
 
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Old 03-28-06, 12:29 PM
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Cooktop: 120/240V, 40A OCPD, minimum #8 conductor

You can re-use your old range circuit for this one but must replace the 50A DP breaker with a 40A DP breaker.

Oven: 120/240V, 30A OCPD, minimum #8 conductor

The oven needs a new circuit run with #8/3 with ground type NM-B (Romex) cable. You need a 30A DP circuit breaker for this one.
 
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Old 03-28-06, 12:41 PM
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Gator: to add to Bens reply

Those were great links with excellent intructions for the electrical.

It also says that you should run 120/240 volts to both units. It makes an exception that if your model only has three wires in the whip that the neutral (white wire) of the branch circuit feeders will be capped off. This is because no neutral would be required as the appliance only requires 240 volts.

You can keep the existing wiring (if its aluminum wiring I would change it out for copper otherwise it will require special connectors).

Also if you have a model that only requires 240 volts and it is the one you are going to put on the new branch circuit wiring then you could run 8/2 copper with ground cable for it. This will not include a neutral since you wouldnt need it and would in turn save you a few dollars. You will have to check the unit when you purchase it.

Conversely if you use your existing 4 wire feeder for a strictly 240 volt new unit you would just cap the white wire as it is unused.

Verify that you actually have the 4 wires in that existing circuit.
 
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Old 03-28-06, 12:42 PM
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Originally Posted by Roger
Can you give the code reference?
See NEC-2005 422.31(B).


Don't we need the voltage requirements before we can determine if a neutral is required?
I don't believe I've seen an oven, cooktop or range that didn't utilize a neutral for a clock, fan, or other 120V portion of the appliance. But that doesn't mean one doesn't exist.

For future use, given the abundance of neutral-using appliances of this sort, pulling a cable with a neutral included would be a prudent design choice, regardless of the actual appliance installed originally, IMO.
 
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Old 03-28-06, 12:49 PM
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Originally Posted by Roger
Can you give the code reference?
NEC 422.31(B). ... within sight or capable of being locked...



> Don't we need the voltage requirements before we can determine if a neutral is required?

No.
 
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Old 03-28-06, 12:55 PM
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Thanks for the code reference. I wasnt up on that one.

I would agree that there a few cooktops and wall ovens without the need for a neutral. There have been enough posts on the forum where they had units that didnt need a neutral that prompts me to ask.... I also agree running a neutral regardless is a good design for the future.

Hope my questions didnt appear to be questioning your knowledge.... more for my education than anything else.
 
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Old 03-28-06, 12:59 PM
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Originally Posted by Roger
Hope my questions didnt appear to be questioning your knowledge.... more for my education than anything else.
I wouldn't mind if you were.
 
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Old 03-28-06, 12:59 PM
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NEC 422.31(B). ... within sight or capable of being locked...
Yes.... thanks


> Don't we need the voltage requirements before we can determine if a neutral is required?
I understand that you are saying... just run a neutral for good future design and both bases are covered... correct?
 
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Old 03-28-06, 01:21 PM
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Originally Posted by Rocky Mountain
I wouldn't mind if you were.
I agree. Just saying "It's Code, or it's in the Code" doesn't help.

Actual NEC articles have an article number and section.

No one should be afraid to ask for the reference.

Definitely no one should be offended when someone asks.
 
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Old 03-28-06, 07:23 PM
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Thanks!

What great information. I appreciate your help. Can you let me know if this sounds right?

I will re-use the existing range circuit for the cooktop and will replace the 50A DP breaker with a 40A DP breaker. This existing circuit is 4-wire (white, black, red, and bare copper)

For the oven I will run a new circuit with #8/3 with ground type NM-B cable using a 30A DP circuit breaker.

I need to hardwire a plug to both the oven and cooktop. I purchased 2 of the following:

Angle Plug 30/50A 125/250V, 3-Pole, 4-Wire

Will this work?

The oven has 4 wires (white, black, red, and bare copper) while the cooktop has 4 wires (white, black, red, and green)

When I hardwire these to the plugs, do I need to make sure black/red of the plugs align properly with the black/red of the receptacle? Does it matter?

Thanks for the great advice!
 
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Old 03-28-06, 08:25 PM
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I will re-use the existing range circuit for the cooktop and will replace the 50A DP breaker with a 40A DP breaker. This existing circuit is 4-wire (white, black, red, and bare copper)
Yes
For the oven I will run a new circuit with #8/3 with ground type NM-B cable using a 30A DP circuit breaker.
Yes, that is what the instructions noted
I need to hardwire a plug to both the oven and cooktop. I purchased 2 of the following:
Angle Plug 30/50A 125/250V, 3-Pole, 4-Wire
Will this work?
No, You dont need plugs... hardwire means to purchase junction boxes and connect the appliance whips wires with wirenuts to the branch circuit feeder wires. I would recommend 4" x 4" x 2 1/8" metal jb's (30.3 inch squared vol.)with covers. Wirenuts that will accomodate the #8 conductors and #10 ground of the NM-B and the appliance whip wires they connect to.. NM-B cable clamps for securing cable to the the JB's. Clamps for the metal flex cable whips of the appliances.

The oven has 4 wires (white, black, red, and bare copper) while the cooktop has 4 wires (white, black, red, and green)
You dont use plugs, but to answer it wouldnt matter if you connected black to red and red to black. However, since this is a hardwire it would be conventional to connect red to red, black to black white to white and bare to green or bare to bare. Dont forget to ground the JB box if metal.
 
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Old 03-28-06, 08:55 PM
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I agree with Roger.

Also, be sure of the exact location where the romex is to stick out of the wall. Wall ovens are persnickety about where the junction box can go - it's usually a tight fit.
 
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Old 03-29-06, 10:17 AM
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Wow, my thoughts of how this should be done has been completely transformed after learning how it should really be done!

The wire from the circuit is much thicker than the wire coming from the appliances. Is it still OK to just use a wirenut to connect these?
 
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Old 03-29-06, 10:32 AM
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Yep, that's perfectly normal. Appliance manufacturers don't have the same rules we do, they can use taps (too small of conductors) for their connection to the house wiring.

Twist the stranded conductors with your fingertips, until the appliance conductor is firmly twisted on the end. Lay it together with the romex conductor. Slide the smaller wire forward a little bit, so that the smaller conductor enters the wirenut slightly ahead of the larger one. Twist on the wirenut until it's good and snug.

You're probably using a blue or blue/gray wirenut, right?

Be sure to ground the junction box, if it's metal.
 
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Old 03-29-06, 09:27 PM
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Great, I'm gonna give this a shot this weekend. Are there cover plates for the junction box that have knockouts to connect the whip to?
 
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Old 03-30-06, 08:04 AM
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Raco makes a model 8753 4 x 4 flat cover with 1/2" center knockout. I believe you should be able to find them at the home centers.
 
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