Electric Cooktop 3-Wire Connection

[hurk27]

hurk27, you confused me with your last posting.
Can I mount the ground wire from the cooktop to the neutral on the receptacle?

Lets untangle two differant things:

First yes if the circuit is existing, then 250.140 will allow you to use the white to connect the bare EGC to it, also as I pointed out that it is allowed to re-identify a white neutral as an EGC by tapeing it at each exposed place in the cable run with green tape, but like I said since this is an existing circuit then 250.140 will allow it to stay as it is and the neutral can be used for the EGC without re-identifying it.

Now the question of connecting this whip to the receptacle.

Because the cook top came with this whip already installed, it might have been required by the manufature to be hard wired, which would amount to removing the receptacle and installing a juntion box such as a 1100B box or even a deep 4x4" box, If the instructions allow for a cord and plug to be used then you can install a 3-wire range cord, but it has to be listed in the instructions that came with the cook top, but to just wire the whip to the receptacle by putting two wires in the same lug would be a violation if the lugs are not listed for two conductors and these on this receptacle most likely are not, also look in the instructions to see if this cook top is allowed to be connected to a 50 amp circuit, if not then just change the breaker to one allowed by the manufacture, I had one that was only listed to be on a circuit not larger then a 30 amp so you have to check the instructions.

Also I mistakingly said you could only use the exception to 250.140 if the cable was fed from the main service panel, but this only applies to the use of SE type cable where the neutral would be the bare concentric conductor of that type of cable, in your case you have regular NM with no EGC so that part doesnt apply as the neutral is insulated.

The code use to not allow the use of the exception if it was in a mobile home, but I see that was removed in 2005.

 

[mike1061]

If you hardwire the range to a box on the wall, what is the means of disconnect?
Thanks
Mike

 

[kwired]

If you hardwire the range to a box on the wall, what is the means of disconnect?
Thanks
Mike

A lock attachment that remains on the breaker even when not in use allows the branch circuit breaker to be the disconnecting means.

See 422.31(B).

 

[hurk27]

Also as has been stated, if the feed is from a sub panel, you need to move the white wire to the ground bar and also tape it green.

For some reason this is what I thought also, but after reading 250.140(3) it clearly only applies if SE type cable was used, also using the exception to 250.140 I don't think the re-identification is required

Here is the commentary to 250.140 in the 2011 hand book:

Where Type SE cable was used
to supply ranges and dryers, the branch circuit was required
to originate at the service equipment to avoid neutral current
from downstream panelboards being imposed on metal objects,
such as pipes or ducts.

This requirement has not been changed back as far as my 1999 NEC, heres what my 1999 NEC says:

250-140(3) 3. The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.

So this is maybe also why they removed mobile homes from not being able to use this exception because it only applied to SE cable? funny thing is that 550.16(A)(1) and (A)(2) still requires separate grounded conductors and grounding conductors so 3=wire connections on ranges and dryers are still is not allowed for mobile homes.

 

[hurk27]

If you hardwire the range to a box on the wall, what is the means of disconnect?
Thanks
Mike

Nice catch, didn't even think about that one, and Kwired addressed it.

He could also put a small cheap pull out A/C disconnect in place of the receptacle and kill two birds with one stone?

 

[Little Bill]

Also as has been stated, if the feed is from a sub panel, you need to move the white wire to the ground bar and also tape it green.

For some reason this is what I thought also, but after reading 250.140(3) it clearly only applies if SE type cable was used, also using the exception to 250.140 I don't think the re-identification is required

Here is the commentary to 250.140 in the 2011 hand book:



This requirement has not been changed back as far as my 1999 NEC, heres what my 1999 NEC says:



So this is maybe also why they removed mobile homes from not being able to use this exception because it only applied to SE cable? funny thing is that 550.16(A)(1) and (A)(2) still requires separate grounded conductors and grounding conductors so 3=wire connections on ranges and dryers are still is not allowed for mobile homes.

I wasn't talking about it not being allowed from a sub panel. I was talking about if it did come from a sub panel, you would need to move the white (neutral) wire from the neutral bar over to the ground bar, since in a sub panel the grounds and neutrals have to be separated.

I know the rule about using SE cable and have had to show more than one person that it only applied to SE cable with a bare neutral.

 

[mike1061]

A lock attachment that remains on the breaker even when not in use allows the branch circuit breaker to be the disconnecting means.

See 422.31(B).

I've herd about this but never seen one.
Thanks
Mike

 

[MAD King]

Hello all, here are more information on the cooktop.

That is the cooktop itself.

This is the installation manual. It says somewhere in it that a 40 AMP breaker should be used. Can't find it right now, maybe it is too early in the morning :blink:

Here is a pic of the circuit diagram of the cooktop

And here a picture if the breaker main panel which has a AMP breaker in for the cooktop or range.

 

[John120/240]

Look Here .....http://www.grainger.com/Grainger/SQ...cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1

These are inexpensive and satisfy the requirement

 

[conmgt]

That is the cooktop itself.

This is the installation manual. It says somewhere in it that a 40 AMP breaker should be used.

Yep, the manual says use a 40A breaker. I wish manuals and online specs would give the actual wattage.
The manual also says wire to a junction box which is what I meant in my previous post about removing the receptacle and installing a box. I wasn't talking about a receptacle on the cooktop itself.

 

[masterinbama]

That particular cooktop has never and still doesn't require a 4 wire circuit. Change the white to green and make sure it's landed on the ground bus if it's fed from a subpanel.

 

[MAD King]

That particular cooktop has never and still doesn't require a 4 wire circuit. Change the white to green and make sure it's landed on the ground bus if it's fed from a subpanel.

All three wires go direct into the main panel.
So no need to replace the white to the ground bar, right?

Thank you

You guys are awesome. :thumbsup:

 

[kwired]

I've herd about this but never seen one.
Thanks
Mike

I'm guessing nearly every breaker manufacturer has one that fits their products. Try looking in the breaker accessories section of catalogs for which ever manufacturer you are interested in. Pretty sure that HD and Lowes sell lock attachments for all the breaker lines they sell, and would guess most electrical supply houses would have some for the lines they sell.

 

[mike1061]

Great, I'll ask at the supply house. I only go to HD when it's necessacery.
Thanks
Mike

 

[conmgt]

All three wires go direct into the main panel.
So no need to replace the white to the ground bar, right?

It should already be on the ground bar and by that I mean any bars with grounds and/or neutrals should already be bonded to each other and bonded to the enclosure. Therefore, your neutral bar and ground bar are one and the same.

 

[kwired]

It should already be on the ground bar and by that I mean any bars with grounds and/or neutrals should already be bonded to each other and bonded to the enclosure. Therefore, your neutral bar and ground bar are one and the same.

You do have to watch for ground bars where the enclosure would become a current path if you are attaching a neutral conductor. This would not really be an issue with the installation in this thread though.

 

[RICK NAPIER]

That particular cooktop has never and still doesn't require a 4 wire circuit. Change the white to green and make sure it's landed on the ground bus if it's fed from a subpanel.

This installation of a three wire feed was only allowed if it originated at the service equipment.

 

[norcal]

This installation of a three wire feed was only allowed if it originated at the service equipment.

If your talking about the OP's photos the neutral is insulated, if my memory serves me the service equipment limitation was when using a uninsulated neutral like in SE cable.

 

[ASG]

Look Here .....http://www.grainger.com/Grainger/SQ...cm_sp=IO-_-IDP-_-RR_VTV70300505&cm_vc=IDPRRZ1

These are inexpensive and satisfy the requirement

Doesn't it have to be pad lockable?

 

[david luchini]

This installation of a three wire feed was only allowed if it originated at the service equipment.

I don't think that is correct. A branch circuit using the grounded conductor as the permitted grounding means for the frame of a range or clothes dryer was required to originate at the service equipment IF the grounded conductor was uninsulated and part of an SE service-entrance cable. If the grounded conductor was insulated, there was no such requirement.

edit: Norcal beat me to it.