Just got new drop in electric stove which has 4 wire 10 gage hookup. Old stove has 3 wire 6 gage cable per my inspection of breaker box. Do I have to replace with 4 wire cable or can I run a single 6 gage wire to box to for forth wire. Stan
What wiring method was used to run the stove circuit to the kitchen originally?
The stove doesn't give installation instructions for 3wire? Then reply to Mr. Horne.
(Is the #6 copper or aluminum? My stove is aluminum 3wire #6 and I plan on replacing it; when the time comes.)
The new stove should have directions for installing on a 3-wire circuit.
If you ever need to extend the old circuit, you'll have to replace it with a 4-wire. Until then, you should be able to keep using it. If it's aluminum cable, be very careful how you connect the wires (de-ox goop, AL7CU or AL9CU connectors, etc.) Silver color doesn't necessarily mean aluminum, some big copper cables have tin plating.
Are you sure the hookup wires are #10 and not #8? (not that it matters, I'm just curious)
Best regards, Bob
No. Sorry that I don't have the specific article in the NEC that says it, but I recall, all wires in a circuit must be housed in a cabled sheath, jacket or raceway. The forth wire would be independent of the original 3 conductor cable, therefore it would violate this requirement.
I'm guessing from what you wrote the forth wire would be a dedicated equipement grounding conductor(since years ago 120/240volt applances were grounded via the neutral wire), so even thought it isn't normally carrying current of the circuit, it's part of the system.
Please, working from memory, so referr to the actual codes(even local) for performing any electrical work.
hth,
tom @
Last time I checked, the NEC allows an equipment grounding conductor to be run seperate from the current-carrying conductors when you are updating old work. If I'm right, and if the original wiring has a red, black, and white wire (or 3 black wires since it's #6), OP could run a separate green or bare wire and bring the existing circuit up-to-date.
My guess is that the old cable is type SE, and he can't add a seperate
4th wire EGC because the cable's grounded conductor is not insulated except by the outer jacket -- it could short out to the EGC at the metal J-box -- and it's not white, nor black with white tape on the ends.I don't know if that makes sense or not; I'm having trouble describing it. My point is the EGC does *not* always have to run with the other circuit wires, but that's unlikely to help in this situation.
Bob
My apologies to folks who answered my prior post. Stove is new unit and I have not pulled old unit yet as replacement is for cosmetic purposes prior to house sale. I found install manual inside of covered drip pan and have hook up directions. Gives both 3 & 4 wire methods. Wires are in metal sheathing coming out of stove, & labeled as 10 gage and are copper.
Seems like for current code (?) I will have to run 4-wire cable unless I can get along with a separate appliance ground wire. Length of run will be 30-35 feet so can I use 8 gage wire if separate run is not allowed?
For current code, you would have to run a new 4-wire cable. But if you don't mess with the old wires, you don't have to meet the current code. Your old wires met the code requirements when they were installed and you can reuse them for the new stove.
You never said what the amps requirement is for the new stove; probably
40A. My code book is at work, but I think (if you really want to run a new cable) you can use #8 copper cable if it is rated 75°C, or you could use #6 aluminum SER. Eight gauge wire is a lot easier to work with than #6 because #8 is much more flexible (it has small strands.)I would just install the new stove on the old 3-wire circuit and be done with it. You're trying to make this more difficult than it is. :-)
Best regards, Bob
Ah you are right, when replacing an ungrounded receptacle it is allowed in certain 'existing' installations.
In the 2002 NEC (2005 hasn't been adopted yet here):
300.3 -> 300.3(B)2 -> 250.130(C)After you do the connect the dots, you can run it seperate.
BTW, still have to check with the local codes, since they might want proof the existing installation is ok first, or they might force you to run a new 4 conductor line.
Remember check with codes before engaging in any electrical work.
Would be nice if it's metal raceway(MC, AC, etc) so just changing the receptale and grounding to a box would suffice.
IMHO,
tom
I understand that if the old work is left undisturbed that it is ok to use a 3 wire connection when installing a replacement appliance.
What I'd like to learn is just what kind of faults and accidents drove the code to require a separate ground conductor for those kind of dedicated 230 volt appliance circuits, mainly clothes dryers and stoves I suppose. By "dedicated" I mean that the circuit only serves one receptical/appliance.
IME the neutral conductor is always well bonded to the equipment housing when a 3 wire installation is used, and that neutral lead is as large as the power leads. The only fault I can envision creating a hazard with that kind of setup is an open in the neutral lead combined with an insulation failure within the appliance.
It would seem that an open in the ground lead of a 4 wire circuit combined with a similar insulation failure in the appliance would create the same kind of hazard.
So why the separate ground nowadays?
Jeff
First off, note that clothes dryers and stoves are *not* purely 240V appliances: the heating elements are 240V, but the control circuits (and, in the case of a dryer, the motor) are 120V and thus need a neutral.
The neutral in a 120V circuit carries current. When the equipment chassis is bonded to the neutral conductor, any person touching the chassis becomes a secondary, parallel path to ground for the return current. Under certain adverse circumstances (e.g. barefoot on a wet concrete floor) the possibility exists for hazardous levels of current to flow through that person - even when there is no fault in the wiring or in the appliance.
Wiring faults (e.g. a high-resistance connection in the neutral) greatly increase this hazard, again even when there is no fault in the appliance.
These risks are essentially eliminated when the neutral is isolated from the equipment chassis, and the chassis is bonded to ground.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
You're correct of course, I considered that parallel path condition and asumed a maximum of 10 amps of motor current flowing on the neutral lead. With 75 feet of No. 10 wire, 10 amps will create only about 0.9 volt of drop in that neutral lead, and I figured that if you could drive enought current through a human body with that low a voltage, even with wet skin, I would have heard about people electrocuting themselves with a single D cell battery by now.
I can't argue with that either.
Yes, as long as the chassis ground doesn't develop a high resistance or open too.
All that said, I have to agree that the fourth conductor does add another level of protection.
Jeff
The key is that if a separate grounding conductor is used, it takes a double-point failure (the ground has to be open AND a hot lead has to contact the chassis) in order to create a life-threatening situation. Using neutral as ground, all it takes is a single-point failure (floating neutral) to produce a threat to life.
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