3-wire to 4-wire conversion for range and dryer outlets

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Our house has 3-conductor wiring for the range and dryer. Would it be OK according to the NEC to run an additional (green) conductor alongside the existing wiring and replace the receptacles by 4-pin ones? If so, what gauge? Or would the existing wiring have to be replaced?
Perce
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Just put 3 wire pigtails on your appliances and get on with life.
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Steve Barker





"Percival P. Cassidy" < snipped-for-privacy@notmyISP.net> wrote in message
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Percival P. Cassidy wrote:

Yes it would be OK, but it's not necessary. (a #10 wire should be adequate for both if you do it anyway) You should not have to replace the old wiring, but that kind of depends on whether the existing neutral wire is insulated.
Bob
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On 06/06/07 01:04 am zxcvbob wrote:

I realize that it's not *required*, but I was thinking that since our new range comes without a cord, I might as well buy a 4-wire one and upgrade the house wiring at the same time. And I assume that the Code change was motivated by safety considerations, not just a desire to sell more copper.
Perce
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wrote:

No, it's not. All conductors for a circuit are required to be in the same raceway or cable. [2005 NEC, Article 300.5(I)]

That's true. Code permits connecting new appliances to *existing* 3-wire circuits, but prohibits installing *new* 3-wire circuits for this purpose.
If it were me, though, and it wasn't too much effort or expense, I'd pull new 4-wire cable.
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Doug Miller (alphageek at milmac dot com)
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On 06/06/07 08:05 am Doug Miller wrote:

Except for a few feet of EMT where the wiring for the dryer outlet come down the wall* (and I could easily get a new ground wire in at the top end to connect to a 4-pin outlet), there are no raceways: the existing wiring comes out of the panel (which is surface mounted, so I could easily run the ground wires out through the same knockout/clamp) and is stapled to the underside of the joists.
*And it's just occurred to me that running Romex in conduit probably wasn't kosher either. I wasn't the one who did it.

That's what I'm trying to decide. Each run is approx. 15ft. What gauge should be used? -- either for a separate ground wire or for whole new wiring runs.
Perce
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I may be wrong, but I thought there were provisions for retrofit to allow for the addition of the ground to existing wiring, Doug?
Myself, even if it weren't _strictly_ NEC, I'd be comfortable w/ adding the ground to the cable and securing it well to the cable every so often so it can't be easily separated nor confused w/ some other cable. Of course, that runs future risk that if try to sell some anal inspector could force you to fix it at the time. Overall, my choice would undoubtedly be to simply continue w/ the 3-wire service unless was rewiring whole house or another major wiring upgrade project anyway.
As for wire size, 10 ga is certainly the norm for the service. What to use is whatever is adequate for the breaker for the existing circuit. I'm not familiar enough w/ the 4-wire code requirements to know if it allows for the "one size under" or not, but for 15-ft of #10 I'd use the full size irrespective.
--


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That was discussed here a few months ago, and IIRC someone posted a Code citation showing that is incorrect.
And even if it were permitted, he still has another problem: the existing Romex cable uses the uninsulated wire as the neutral. This [probably] met Code at the time of installation, but it doesn't meet it now. As long as the circuit is left alone, it's compliant -- but when it's modified, it needs to be brought into compliance with Code in effect at the time of modification. And that means an insulated neutral which he doesn't have.

Not so fast there. He said "range and dryer". 10ga is fine for most dryers, but it is probably NOT adequate for an electric range.

Not correct.
What to use is whatever is correct for the current ratings of the existing appliances. You are assuming that the existing conductors and breakers are properly sized to the appliances. Probably a valid assumption, I grant you, but an assumption nonetheless, and one which ought to be verified.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

I looked it up on Google from where I posted the information about 5 years ago. It's section 250-50:
"For replacement of nongrounding-type receptacles with grounding-type receptacles and for branch circuit extensions only in existing installations that do not have an equipment grounding conductor in the branch circuit, the grounding conductor of a grounding-type receptacle outlet shall be permitted to be grounded to any accessible point on the grounding electrode system as described in Section 250-81."
Of course it's possible that this has changes since 2001. (But I doubt it because it makes too much sense. Without this exception, people would just leave things ungrounded.) HTH :-)
Bob
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The grounding conductor is allowed to be smaller than the hot and neutral conductors for circuits at 40A and higher. Below that, the minimum size for the grounding conductor is the same as the minimum size for the hot and neutral. [2005 NEC, Table 250.122]
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Doug Miller (alphageek at milmac dot com)
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Doesn't matter, it still doesn't meet Code. Note the word "cable" in the part I cited. It absolutely is a Code violation to run another conductor of the same circuit alongside the existing cable.
Moreover, the NEC no longer permits the use of uninsulated neutrals, which is what you have in the existing cable. It met Code at the time it was installed, but if you modify the circuit, you're required to bring it up to *current* Code -- and that requires the neutral to be insulated. You can't achieve that with the cable you have now.

Despite repeated posts in this ng from certain individuals who claim that Code doesn't permit Romex (technically, NM cable) in conduit, it's actually perfectly fine for above-ground installations.

Gauge depends on amperage. For 30A, you need 10-ga copper; for 40A or 50A, 8-ga.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

305-I is underground (buried). You want 300.3-B.

There is an exception in 300.3-B. Separate grounding conductors can be run for receptacles on existing ungrounded circuits (or extensions of existing ungrounded circuits), connected as in 250.130-C.

I agree that the uninsulated neutral is a fatal problem, so to speak.

It is a common practice to run Romex down a wall in EMT to protect it.

Grounding conductors are sized from 250.122. #10 is OK for up to a 60A circuit.
--
bud--


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Of course, "305-I" is not what I wrote. Look again.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

Sorry - my fingers didn't type what I told them to. Should have said 300.5-I - which is underground (buried). 300.3-B is appropriate.
-- bud--
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You're right, my fault -- same provision, but a different part of the Code.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

There's an exception that allows an equipment ground to run separately when upgrading old work. I can't quote the article number cuz I loaned out my code book.
Bob
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wrote:

250.130(C). It's pretty narrowly drawn, but might apply here.
Just the same, what the OP proposes still doesn't meet Code due to an uninsulated neutral. Probably met Code at the time of installation, but won't meet it now, which it needs to if the circuit is modified.
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Doug Miller (alphageek at milmac dot com)
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Doug Miller wrote:

I agree about the uninsulated neutral (I even mentioned that earlier.) My old house had SE cable for range, then at some point they put in a gas range and just rerouted the old range cable to the dryer (and refused it at 30A.)
I think OP should just leave everything alone and use a 3-wire circuit. He could also leave the wiring alone and separate the ground from the neutral at the dryer (remove the bonding strap and run a separate ground wire from the frame back to the panel box.) That way he gets the equipment ground he wants without altering the wiring.
Bob
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On 06/06/07 11:58 am zxcvbob wrote:

The new range was just delivered, and the delivery guy said, "We've got a 3-wire cord here if you want it" (I hadn't ordered or paid for it), so I accepted their kind offer.
Perce (OP)
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That's certainly the simplest.
If it turns out that the power requirements of the new range exceed the capacity of the existing circuit, Code requires that the new circuit be 4-wire.
--
Regards,
Doug Miller (alphageek at milmac dot com)
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