Old dryer on 10-2 wiring.

[deckscrew]

I recently bought and older house, (c. 1940's) with the intention to renovate it. The previous and original owner had a lot of time to make a lot of illegal modifications to the house. I had an electrician come in and clean up a few items before we moved in.

We found the dryer had been wired with 10-2 cable. The ground wire used as the neutral wired back to the service. There was a ground wire attached from the dryer's ground screw to the washer's ground screw. The washing machine is on a grounded GFCI circuit.

Ultimately the laundry will be relocated and the dryer replaced with a gas unit, but not for another 9-12 months. The electrician thought it would be OK for the time being. Replacing the wiring would be a pain and involve cutting open a lot of walls. Also there is no disconnect at the service entrance so he'd have to pull the meter.

Is the electrician correct or am I in danger of burning my house down? Your comments are greatly appreciated and always informative.

Thanks.

 

[kwired]

Though it was improper to use 10-2 W gnd, a 10-3 with no ground would have been acceptable. Not really too much difference in performance between the two.

I would lose the jumper wire to the washer though, all that is doing is paralleling neutral current from the dryer to the washer EGC, assuming the dryer has the bonding strap installed properly.

 

[Dennis Alwon]

I doubt you will burn down your house with that install. If the cable originates at the service panel then it was legal to use 10/3 SEU cable. The only difference is the neutral/ ground is stranded and wraps around the other conductors. Not sure why that was okay and not 10/2 nm

 

[deckscrew]

I think it was done by the previous owner. These houses typically have the washer and dryer in the basement. He put them upstairs in a bedroom and probably used whatever wire was available.

 

[curt swartz]

I doubt you will burn down your house with that install. If the cable originates at the service panel then it was legal to use 10/3 SEU cable. The only difference is the neutral/ ground is stranded and wraps around the other conductors. Not sure why that was okay and not 10/2 nm

Up until the mid 70's the grounding conductor in 14-10 NM cable was smaller than the current carrying conductors. The grounding conductor in NM cables 8 and larger are sill reduced sizes. This smaller conductor would not be suitable for use as a neutral conductor. The grounding conductor in 10-6 SE cable is full sized

 

[Dennis Alwon]

True yet they allow a reduction in neutrals for cooking appliances 210.19(A)(3)

 

[GoldDigger]

True yet they allow a reduction in neutrals for cooking appliances 210.19(A)(3)

And in this particular case, I doubt that the neutral load from the dryer will be very large. Heating element should be pure 240 and motor may or may not be 240. Timer controls and lights would be the sure candidates for 120.

 

[templdl]

I believe your installation is grandfathered into the NEC. The most important thing that you can do is to examine the existing combination neutral/EGC to assure that there are no breaks in it and that it is continues all the way back to the panel and not shared with anything terminated securely to the grounded neutral bar.
My range in home was 2w with the combo neutral ground which I replaced with 3w with ground because it was accessible.
One thing to keep in mind is that grounding conductors are bonded to enclosures and neutrals do carry current. As such when you combine a neutral and grounding conductor should that conductor become compromised between the appliance and the panel at which it is terminated you will be turning the neutral current loose on the enclosure on the appliance that will create a shock hazard. As such assuring the integrity of that N/gr conductor is imperative.

 

[readydave8]

I believe your installation is grandfathered into the NEC. The most important thing that you can do is to examine the existing combination neutral/EGC to assure that there are no breaks in it and that it is continues all the way back to the panel and not shared with anything terminated securely to the grounded neutral bar.
My range in home was 2w with the combo neutral ground which I replaced with 3w with ground because it was accessible.
One thing to keep in mind is that grounding conductors are bonded to enclosures and neutrals do carry current. As such when you combine a neutral and grounding conductor should that conductor become compromised between the appliance and the panel at which it is terminated you will be turning the neutral current loose on the enclosure on the appliance that will create a shock hazard. As such assuring the integrity of that N/gr conductor is imperative.

The 3/cdtr may be grandfathered but was 10/2 with bare ground ever legal? I remember my choices being 10/3 (without ground--I would specify "plain" or "with ground" at supply house) or SE cable.

 

[kwired]

The 3/cdtr may be grandfathered but was 10/2 with bare ground ever legal? I remember my choices being 10/3 (without ground--I would specify "plain" or "with ground" at supply house) or SE cable.

That is my thought also, 10-2 with ground was never allowed AFAIK. It had to be an insulated neutral or SE cable.

 

[templdl]

The 3/cdtr may be grandfathered but was 10/2 with bare ground ever legal? I remember my choices being 10/3 (without ground--I would specify "plain" or "with ground" at supply house) or SE cable.

Was it bare ground or a combo ground/neutral. Isn't that cable considered a type of non-metallic consisting of 2 insulated line conductors with bare 3rd conductor for the combo neutral grounding conductor. It is of my opinion that it's just something that I would recommend keeping if it can be updated. I'm surprised that there haven't been more accidental shocks.

 

[kwired]

Was it bare ground or a combo ground/neutral. Isn't that cable considered a type of non-metallic consisting of 2 insulated line conductors with bare 3rd conductor for the combo neutral grounding conductor. It is of my opinion that it's just something that I would recommend keeping if it can be updated. I'm surprised that there haven't been more accidental shocks.

If there is only three conductors you have no choice if you are going to use that particular cable but to use one for grounding and for neutral, and it will not matter if it is insulated or bare.

The NEC (and I don't know how far back) had for a long time required this grounded conductor to be either insulated with white color, or be the concentric bare conductor of a type SE cable. It never allowed the usual equipment grounding conductor in a 2 wire with ground cable to be used for both grounding and for neutral. I wouldn't get concerned that the OP has something that needs immediate attention, electrically it is nearly the same as a cable that would have been compliant.

 

[templdl]

If there is only three conductors you have no choice if you are going to use that particular cable but to use one for grounding and for neutral, and it will not matter if it is insulated or bare.

The NEC (and I don't know how far back) had for a long time required this grounded conductor to be either insulated with white color, or be the concentric bare conductor of a type SE cable. It never allowed the usual equipment grounding conductor in a 2 wire with ground cable to be used for both grounding and for neutral. I wouldn't get concerned that the OP has something that needs immediate attention, electrically it is nearly the same as a cable that would have been compliant.

I don't believe I implied that it needed immediate replacement. My comments only stated what the importance on maintaining the integrity of that combo neutral/grounding conductor. It should be continuous from the appliance to the panel with no splices. That if that connection is compromised bad things could happen. I'm sure that tens of thousands of these installations exist today without incidence and as such have not posed to be any hazard. The current code just shows how far the respect for separate neutral and grounds have come. Even though I may not be required I updated mine in my home mainly because it was easily accessible as well as the labor was free.
Good discussion though.

 

[jmellc]

The 3/cdtr may be grandfathered but was 10/2 with bare ground ever legal? I remember my choices being 10/3 (without ground--I would specify "plain" or "with ground" at supply house) or SE cable.

I helped wire a lot of new houses & apts in the 70's with 10-2 NM, bare ground and they always passed inspection. Mobile homes were the 1st app I recall that demanded 4 wire dryer and range ckts, several code cycles before house and apts if I recall correctly.

 

[readydave8]

I helped wire a lot of new houses & apts in the 70's with 10-2 NM, bare ground and they always passed inspection. Mobile homes were the 1st app I recall that demanded 4 wire dryer and range ckts, several code cycles before house and apts if I recall correctly.

Yes I believe you that they passed inspection. This may or may not prove that practice was allowed by NEC. When did NEC allow bare conductor in 10/2 wg to be neutral for dryer? I started in late 70's and was never familiar with earlier codes.

 

[kwired]

Yes I believe you that they passed inspection. This may or may not prove that practice was allowed by NEC. When did NEC allow bare conductor in 10/2 wg to be neutral for dryer? I started in late 70's and was never familiar with earlier codes.

I could be wrong, but I don't think it was ever allowed. Even back in the days when you didn't have many 120 volt circuits with a grounding conductor, they always ran either SE cable or three insulated conductors to ranges and dryers.

 

[jmellc]

Truth is, the couple of years I worked in the 1970's, I didn't read code that much. Believe it or not, we were not encouraged to stay up on code & it didn't occur to me to do it on my own. The office managers told us what to use. We commonly ran 10-2 w/g for dryers & 6/2 w/g for ranges. I saw countless older installs done the same way. I did also see older dryer installs with 10-3 no grnd. I can't think code disallowed it for it to be that common on inspected jobs. The inspector in that town was not that lenient. Best I recall, we did install 4 wire dryer & range ckts in mobile homes, the little we worked on them.

 

[readydave8]

Old NEC

Old NEC

I was able to dig out '65 and '75 but nothing inbetween.

1965 NEC:

"250.60. Frames of Electric Ranges and Electric Clothes Dryers

. . .they may be grounded by connection to the grounded circuit conducors. . ."


No mention of bare or insulated, but same edition:

"336.2 . . .the cable may have an . . .uninsulated or bare conductor for grounding purposes only."
(refering to NM cable).


1975 NEC:

"250-60. [same title] . . .(c) The grounded conductor is insulated. . .or. . .part of a service entrance cable and the branch circuit originates at the service equipment."

So using bare in 10/2 for dryer "neutral" was definitely violation of 1975 NEC and probably of 1965 as well?

 

[jmellc]

I was able to dig out '65 and '75 but nothing inbetween.

1965 NEC:

"250.60. Frames of Electric Ranges and Electric Clothes Dryers

. . .they may be grounded by connection to the grounded circuit conducors. . ."


No mention of bare or insulated, but same edition:

"336.2 . . .the cable may have an . . .uninsulated or bare conductor for grounding purposes only."
(refering to NM cable).


1975 NEC:

"250-60. [same title] . . .(c) The grounded conductor is insulated. . .or. . .part of a service entrance cable and the branch circuit originates at the service equipment."

So using bare in 10/2 for dryer "neutral" was definitely violation of 1975 NEC and probably of 1965 as well?

So it appears. I am surprised and humbled by this. In 1976 and 1977 I did this in Wilson, NC all the time and for a short time working around Goldsboro, NC. Inspectors must not have thought it a very important issue for they sure passed them and anyone could see we used 10-2, not 10-3. I recall a few large apt buildings where we did 3 wire with 10-2, space after space. 10 or so apts per building.

 

[jmellc]

Readydave, upon further thought, maybe the inspectors did their own "simplifying". Since bare service cable neutrals were allowed, maybe they didn't see a problem with bare neutrals from NM cable. BTW, I not only installed them in Wilson and Goldsboro areas of NC, I have seen many from the same era in central NC; Durham, Raleigh, Chapel Hill and surrounding areas.