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We are moving our range across the kitchen and need to extend the 50a 6/2 line which has an aluminum ground. The only line the home store had was 6/2 wire with 10awg copper ground. Can I use that or do I need to find identical wire? I am planning to use a large junction box and have large wire nuts to join the wires. Really don't want to replace the whole line.

brhans
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Jim
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    There is some disagreement even among inspectors about whether the code allows extending 3-wire range and dryer circuits. The NEC exception refers to existing circuits, and many determine that extending the circuit requires bringing up to current code. – NoSparksPlease Jul 02 '20 at 00:41
  • Is this a very old range? The original builder quality range in our 1970 tract home was 3-wire plus gnd. Are there ranges that do not need a neutral? Is this range operating entirely at 240 V? – Jim Stewart Jul 02 '20 at 01:08
  • @JimStewart -- there are only a handful of ranges that do not need neutral – ThreePhaseEel Jul 02 '20 at 03:02
  • Can you post a photo of the inside of the box where the existing line terminates? Also, is there any way to run a ground wire from that terminating box back to the panel, or to the wire from your panel to the cold water pipe/ground rods for that matter? – ThreePhaseEel Jul 02 '20 at 03:03

2 Answers2

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Completely unusable. It was installed illegally from the start, and it’s illegal even if you didn’t move the range.

Once upon a time (prior to the mid 1990s) it was legal to install a range with certain special 3-wire cables. You could never have used /2+ground cable. You could have used:

  • Cable with an insulated white neutral (i.e. /3 no ground). But of course that quickly went extinct after grounding started to be required in the 1960s.
  • SE cable specifically, which is made for service entrances, and has a “meshed” bare conductor which is actually designed to be neutral. However that stopped having a reason to exist in #8/#6 after power companies stopped offering 60A service and set 100A as minimum.

NFPA’s purpose was to allow suppliers to use up their old stock of the above cables... and after that, everyone would be forced to use /3+ground. Well, some installers thought that gave them permission to use /2+ground. They were wrong.

Not least, the ground wire is too small to be safe as a neutral.

So the whole homerun needs to be dropped in the dust-bin, and re-run from scratch with proper wire.

You can run it in aluminum if you really, really want to... that’s not the issue... but it has to be /3+ground, and it has to be a 4-wire connection. You have no grandfathering and it must be done to modern spec.

Harper - Reinstate Monica
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  • I wouldn't go to the dust bin, I'd make a stop at the recycle bin - that's a fair bit of copper. It will help (a bit) to offset the cost of the new cabling. – FreeMan Jul 02 '20 at 12:54
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3 wire outlets for ranges/dryers are a bit of an anomaly, and were often not installed completely compliant to code initially, so asking if a modification is legal raises more questions than answers.

For at least 20 years the code has required a separate ground and neutral wires for appliances. Dryer and range circuits before that were allowed to be grounded via the neutral conductor. When the code was changed a code exception was written to allow existing installations to remain, providing it met several conditions. Two that come into play are that the minimum size of the neutral be #10 copper or #8 aluminum and the the neutral be insulated or uninsulated and part of Service Entrance cable that originates at the service equipment.

Whether you could extend a circuit that was installed correctly is up to interpretation of the local electrical inspection authority, since the code allows use of 3-wire receptacles only on existing circuits.

Changing from aluminum to copper is not a problem as long as the conductors are of sufficient ampacity, proper aluminum to copper connectors are used, and the circuit was properly installed to start with.

But an issue is you called the wire a ground, that raises questions. If it is a bare wire part of an SE cable or an insulated white wire then it can be used as a neutral, and you can use it on a 3 wire circuit that grounds via that wire, if it's the right size, and you used connectors Listed for use with copper to aluminum connectors.

If the ground is an insulated green wire then it can't be used as a neutral, it doesn't satisfy the requirements of the code exception, and you could not legally extend it.

NoSparksPlease
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