replacement wire size

[jamesgang]

n which case the answer is going to be different.

wiring it to a 3 wire outlet then you may do that. If the appliance hardwi res in then no.

o either a 3 wire or 4 wire installation. Every install manual I've seen

pliant and you're not required to run new wiring back to the panel.

newer stoves with electronics often do that. Not sure why since they could just as easily have their switching power supply for the electronics work on 220. In any case they probably need a 4 wire circuit and I'd go with #6 just so I never had to mess with it again.

Some inspectors will consider a hardwired appliance a change to the wiring and require you to upgrade to code. Not all but some.

Sure, they ran the analog clocks on 110 you used to see in the middle of th em.

[trader_4]

ove location.

in which case the answer is going to be different.

r wiring it to a 3 wire outlet then you may do that. If the appliance hard wires in then no.

to either a 3 wire or 4 wire installation. Every install manual I've seen

ompliant and you're not required to run new wiring back to the panel.

e newer stoves with electronics often do that. Not sure why since they cou ld just as easily have their switching power supply for the electronics wor k on 220. In any case they probably need a 4 wire circuit and I'd go with #6 just so I never had to mess with it again.

g and require you to upgrade to code. Not all but some.

Maybe some inspector, somewhere will, but it's obviously the exception, otherwise all the manufacturers of ovens and stoves would not include instructions on how to wire the appliance into either 3 wire or 4 wire. If it was a code violation or not acceptable to most inspectors, it would be totally irresponsible.

[gfretwell]

It probably should be pointed out that the change in the 96 code was simply as an attempt by Phil Simmonds to create uniformity, not because there was a pile of bodies to justify it. The quote was "the war is over" in reference to copper shortages in the 1940s that prompted the exception.

I have a 3 wire dryer circuit and I have no intention of changing it any time soon.

BTW if your dryer is wired with Romex, legally, you probably have 4 wires in the cable anyway so fixing it is trivial. 10/3 without a ground is pretty rare and the neutral is required to be insulated so

10/2-wg was not legal. The one that was legal was 10/2 -wg SE cable as long as it was fed from the main panel (where the service disconnect and main bonding jumper resides). I never understood why that SE cable exception existed but it was there.

[trader_4]

Would you prefer it if it costs $1000 extra to run a new 4 wire cable back to the panel? The comparison with the outlet isn't a good comparison, because it's never been code to wire an outlet with the neutral and ground shared. In the case of existing oven circuits, it's permitted and common. From a technical perspective, a general purpose outlet is typically different than a dedicated hardwired oven or oven receptacle. In the case of outlets, there are typically multiple outlets, lights etc on a circuit, more places for connections to come loose or other problems to crop up. In the case of an oven, the shared neutral/grd is on a dedictaed 8 gauge or better cicuit from the panel to the appliance.

Is 4 wire better and required for new circuit runs? Yes. Would I go changing an otherwise adequate 3 wire circuit to 4, just to replace an oven? No. Apparently all the oven manufacturers agree, because every oven install manual I've seen shows how to connect it to either a 3 wire or 4 wire circuit.

[dpb]

...

The point is, it _IS_ "to Code" and would be highly unlikely imo to find a local Code that isn't as well in this particular regard.

And inspectors have been known to be wrong or overly zealous, too...

[dpb]

...

I, for one...there's 75+ yr of existing practice that hasn't demonstrated any real problem.

When had repair on the well a couple of summers ago, the well service guys used section of 4-wire cable to replace the torn up section because they said the current county Code req'd it as only they could run. Of course, they then clipped the ground conductor on both ends since there's nowhere for it to go, anyways. About as stupid as blindly replacing a 3-wire for a 4-wire in a range/electric dryer app.

[Scott Lurndal]

And anonymous posters on the internet are authoritative?

I'd advise someone to get advice from a local professional, not from alt.home.repair.

[trader_4]

Not always, but I'd say appliance installation instructions from dozens of manufacturers of ovens, ranges, dryers is. And they all say that you can hook it up to an existing 3 wire or 4 wire circuit. Also there is the NEC.

OMG, someone is gonna die!

I guess we should all just pack up and close down AHR, because you don't know the answer. The same could be said of most of the questions on AHR. Good grief.

[dpb]

...

What about "anonymous" posters who happen to have read/know what the NEC actually says?

"250.140 Frames of Ranges and Clothes Dryers

Frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be connected to the equipment grounding conductor in the manner specified by 250.134 or 250.138.

Exception: For existing branch-circuit installations only where an equipment grounding conductor is not present in the outlet or junction box, the frames of electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes dryers, and outlet or junction boxes that are part of the circuit for these appliances shall be permitted to be connected to the grounded circuit conductor if all the following conditions are met.

The supply circuit is 120/240-volt, single-phase, 3-wire; or

208Y/120-volt derived from a 3-phase, 4-wire, wye-connected system.

The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.

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.

Grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment."

[seagirt555]

Ahmen to that brother!

[dpb]

On 7/1/2014 10:37 AM, [e-mail] wrote: ...

Excepting that Cu is so pricey now that folks are ripping up installed AC units and stripping ground wires from power poles and the like...so let's just willy-nilly drive needless usage/demand/price even higher. Makes sense to me... :(

Certainly wasn't rare at all back when many of these installations were put in.

Because SE cable covering is rated for the voltage insulation whereas NM outer jacket may not be; it's an outer sheath to hold the conductors together physically with some insulating property but not qualified as insulated per UL listing/Code.

[dpb]

...

Besides the aforementioned Code exception that doesn't require and expressly permits the continued usage of 3-wire in existing applications, there are a number of alternatives for rework/existing work allowed by Code to add the ground if that is really, really, really wanted besides running a new 4-wire cable the full distance.

These include pulling a separate ground and also exceptions that that added ground doesn't necessarily have to follow the same path or even be grounded at the same terminus. For the specifics see the Code or consult local Code gurus.

[gfretwell]

[dpb]

On 7/1/2014 11:52 AM, dpb wrote: ...

ADDENDUM to this story...

I've not researched this point in detail but I think this is a place where the requirement quoted above is, in fact, a case of misinterpretation of the NEC requirements as there is for the well pump nothing but a single 240V load; there is no neutral current return from a 120V circuit as is the situation trying to be avoided by the update to the Code as there is in the case of the range or dryer.

Turns out we may be forced to drill a new well before long; I'm certain to research this in depth (so to speak :) ) before spending an extra third for 4-wire down a 300-ft hole when there's nothing for that fourth conductor to do anyway except take up space and add to the expense.

If I'd been on the NFPA Code Committee when this came up I'd have voted "no" simply on the cost/material basis of there being no demonstrable real problem being solved that justified the added expense. "Parsimony" is a virtue in engineering, too...

[trader_4]

I would agree that the well situation is a misinterpretation of the code by someone. Even in cases where you think the code section is excessive on some point, I've always been able to see some point to doing it. To insert a section of 4 wire cable in the middle of a 3 wire and leave the 4th unconnected, obviously does nothing. Also, 240V loads are routinely connected and are code compliant without a neutral all the time. That's how wells are done here. So, I'd say either this is the well guys that don't know what they are talking about, or else some local inspector type that issued some edict either incorrectly or incorrectly interpreted, etc.

I agree.

Do you have any reason to believe it's part of the NEC?

A, as you say, it makes no sense at all from any physics

B, wells here are put in with 240V, 2 hots + ground all the time and they pass electrical inspection.

[dpb]

...big snip...

...

I was mixing both topics here and switched back once too quickly, apparently... :)

No, I do _NOT_ think there's likely anything in NEC that justified the

4-wire cable in the well-hole; I have yet to discover from whence came the supposed edict referred to by the well service guys...

What I was speaking of in the "voting against" comment is the new section that requires the 4-wire for the grounding of the oven/dryer branch circuit. There as you I do see there is at least an issue; I just don't agree that the disease is worth the cost of the cure given the history (or more correctly, the lack thereof) indicating it is a safety issue of any magnitude at all.

I obviously wasn't in the room but I'd have had to seen an impressive litany of cases where it had been the root cause of a problem and if that were to have been demonstrated then I don't see how it could have been justified to leave the exception standing. Making the change was, imo, just bureaucracy doing what it does in this case. Most of the time NFPA does a pretty good job but I think they misstepped on this one.