One for the old timers; Bare neutral?

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I'm in a discussion on the issue of whether people ever used 10/2 W/G as a feed for a 240V circuit that needed a Neutral. Someone is arguing that it was allowed until 1996 and that lots of dryers were wired with 10/2-w/G. I got my license in 1978 and at that time, Neutral was considered a "current carrying conductor" and had to be insulated. That 10/2-w/G may be true, because on a 10-30R the bent prong is the GROUND, not a neutral and although the neutral (if any) inside of the dryer was often bonded to the Ground to be able to power the time clock, technically the bare copper wire in the cable feeding this was not really considered a "neutral" conductor. Am I wrong?
 

infinity

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Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I believe that Dennis nailed it. SE cable was specifically permitted at one time but NM cable never was.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
on a 10-30R the bent prong is the GROUND, not a neutral and although the neutral (if any) inside of the dryer was often bonded to the Ground to be able to power the time clock
My understanding is the opposite, the bent prong is a neutral prong, and the receptacle is a non-grounding type. NEMA 6 is the hot-hot-ground 240V only grounding type receptacle.

So with a NEMA 10 plug and cord, the case is bonded to the neutral. Aren't dryer motors often 120V? So there's more current on the neutral than just the time clock.

Cheer, Wayne
 

KDough

Member
Location
San Jose, CA
Occupation
Electrician 42 yrs / Electrical Inspector 4yrs
That is not true. We used to use 10-2 romex all the time for dryers All the time. Heck I even bought 10-2 to wire up my dryer outlet about 5 years
My understanding is the opposite, the bent prong is a neutral prong, and the receptacle is a non-grounding type. NEMA 6 is the hot-hot-ground 240V only grounding type receptacle.

So with a NEMA 10 plug and cord, the case is bonded to the neutral. Aren't dryer motors often 120V? So there's more current on the neutral than just the time clock.

Cheer, Wayne
ago. Then when the new dryer arrived I got in place and said oh shirts it takes a neutral. Years ago dryers and ranges did not use a neutral because they were all anolog or mechanical controls. They only needed two hots and a ground. I felt pretty stupid as I drove back to Home Depot and bought some 10-3.
I just went over 250.140 and 250.142. There is an exception for dryers where you can ground the metal parts with the grounded conductor but I did not see anything that says you can do the opposite. Meaning you can not use the equipment ground as the grounded conductor (neutral). But I’m telling you in the late 70’s we used 10-2 for dryers and 6-2 & 8-2 for ranges and stove tops all the time with the blessing of the AHJ.
 

OldSparks

Member
Location
Vacaville CA USA
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Retired: Electrician, Submarine Electronics (21 years), Potable water system maintenance boss (21 years).
"But I’m telling you in the late 70’s we used 10-2 for dryers and 6-2 & 8-2 for ranges and stove tops all the time with the blessing of the AHJ." KDough

Agree. I wired a bunch of houses in the Morro Bay, Cayucus, Cambria CA areas in the late 60's and we ran 10-2 NM for all of them.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
My understanding is the opposite, the bent prong is a neutral prong, and the receptacle is a non-grounding type. NEMA 6 is the hot-hot-ground 240V only grounding type receptacle.

So with a NEMA 10 plug and cord, the case is bonded to the neutral. Aren't dryer motors often 120V? So there's more current on the neutral than just the time clock.

Cheer, Wayne

This matches my understanding.

'Three wire' dryer receptacles were wired Hot-Hot-Neutral, and the _Neutral_ was permitted to bond the frame.

The bare 'neutral' conductor of SE cable was permitted for supplying the neutral of NEMA 10-30 receptacle, but the bare 'EGC' conductor of NM cable was not permitted for the same use.

As a practical matter I don't see a huge difference using the between the two cases (bare SE cable conductor vs bare NM conductor). Perhaps this has to do with the history of the size of the bare conductors.

I am sure that using the bare conductor from NM was common practice in some areas, and that it was permitted by some inspectors, but IMHO it was never actually compliant with the words of the code.

-Jon
 

retirede

Senior Member
Location
Illinois
If the dryer is a straight 240v, yes then you can use 10/2 however if you used 10/2 nm for a dryer that required a neutral then your installation was non-compliant.

When wiring a new house, you wouldn’t have known that. You were simply wiring the receptacle. And back then, it was a NEMA 10-30.
 

readydave8

re member
Location
Clarkesville, Georgia
Occupation
electrician
Never seen straight 240v range or dryer, based on the fact that I've always seen a white hooked to neutral on terminal block

Seen a lot of dryers wired with 10/2 but never been allowed by NEC
 

kwired

Electron manager
Location
NE Nebraska
That is not true. We used to use 10-2 romex all the time for dryers All the time. Heck I even bought 10-2 to wire up my dryer outlet about 5 years

ago. Then when the new dryer arrived I got in place and said oh shirts it takes a neutral. Years ago dryers and ranges did not use a neutral because they were all anolog or mechanical controls. They only needed two hots and a ground. I felt pretty stupid as I drove back to Home Depot and bought some 10-3.
I just went over 250.140 and 250.142. There is an exception for dryers where you can ground the metal parts with the grounded conductor but I did not see anything that says you can do the opposite. Meaning you can not use the equipment ground as the grounded conductor (neutral). But I’m telling you in the late 70’s we used 10-2 for dryers and 6-2 & 8-2 for ranges and stove tops all the time with the blessing of the AHJ.
Just because your inspector let you do it doesn't mean it was in compliance with what NEC said. Fairly certain that the mentioned use of SE cable was allowed then and probably back until at least 1940's or 50's but not the bare conductor of NM cable. I haven't seen many dryer circuits that date back that far, but have seen many range circuits that do and they were always SE cable. Wasn't seeing much for NM to ranges for original installs until into the 1970's, and almost always was 6-3 or 8-3 (no ground) when I did encounter it.

And there wasn't even inspections around here back then.
 

hillbilly1

Senior Member
Location
Atlanta,Ga
Occupation
Field coordinator/ technical support
My understanding is the opposite, the bent prong is a neutral prong, and the receptacle is a non-grounding type. NEMA 6 is the hot-hot-ground 240V only grounding type receptacle.

So with a NEMA 10 plug and cord, the case is bonded to the neutral. Aren't dryer motors often 120V? So there's more current on the neutral than just the time clock.

Cheer, Wayne
You are correct, most dryer motors are 120, the reason is, dryers can be ran on 208 or 240, the heating elements don’t care, just takes longer to dry. Motors on the other hand, may not like 208, so in order to make the dryers somewhat universal, they use 120 volt motors and timers.
 

kwired

Electron manager
Location
NE Nebraska
You are correct, most dryer motors are 120, the reason is, dryers can be ran on 208 or 240, the heating elements don’t care, just takes longer to dry. Motors on the other hand, may not like 208, so in order to make the dryers somewhat universal, they use 120 volt motors and timers.
Might depend on how tightly designed the motor is to the load, if not loaded too heavily many 240 volt designed motors can run @ 208.

Another possibility might be they once used same 120 volt motor on both gas and electric dryer of same product line.
 

Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
It is my understanding that the shared neutral/ground conductor was allowed starting in the 1940s with wartime rationing of materials. In the ensuing decades, dryers were almost always wired that way with a NEMA-10 3-wire receptacle. Only relatively recently (OP said maybe 1996) was it required to use four wires (two hots, neutral, and EGC) and a NEMA-14 receptacle, and not bond the ground to the neutral where the cord enters the dryer.

I, like others here, have never seen one wired with type SE cable. Maybe it's a regional thing, but around here the 3-wire dryer receptacles are always wired with 10/2 NM cable (unless it's in a commercial setting with conduit), and I was unaware that the code required a specific cable type.
 

tesi1

Member
Location
florida
when electric dryers came onto the market in the 1920's or 1930's a very large number of houses still only had 120 volt services, the dryers
where made so they could be sold for use on 120 or 120/240, the only difference was you would move 1 wire over on the terminal block for
use on 120 ( it would take 3 to 4 times longer to dry this way ).
 

kwired

Electron manager
Location
NE Nebraska
It is my understanding that the shared neutral/ground conductor was allowed starting in the 1940s with wartime rationing of materials. In the ensuing decades, dryers were almost always wired that way with a NEMA-10 3-wire receptacle. Only relatively recently (OP said maybe 1996) was it required to use four wires (two hots, neutral, and EGC) and a NEMA-14 receptacle, and not bond the ground to the neutral where the cord enters the dryer.

I, like others here, have never seen one wired with type SE cable. Maybe it's a regional thing, but around here the 3-wire dryer receptacles are always wired with 10/2 NM cable (unless it's in a commercial setting with conduit), and I was unaware that the code required a specific cable type.
That 1996 code may seem recent, but it is starting to get close to being midway between now and that WWII time period.
 

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
When wiring a new house, you wouldn’t have known that. You were simply wiring the receptacle. And back then, it was a NEMA 10-30.

Unless you read the code. hahaha It would have required an insulated conductor for the neutral/ground
Never seen straight 240v range or dryer, based on the fact that I've always seen a white hooked to neutral on terminal block

Seen a lot of dryers wired with 10/2 but never been allowed by NEC
I have wired a few but I always ran the extra conductor in case they changed the appliance. I think wolf has a few straight 240 ranges and ovens. I think Miele makes a straight 240v dryer
 

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
We use to be able to buy rolls of 10/3 NM with no ground and an insulated neutral.
Yep, that is what we used for a long time. I remember I was working in Durham and I ran 10/3 but the home owner decided on a gas dryer. No problem so I taped the red wire green (OMG) and the inspector caught it. I explained that I didn't want to strip the insulation off in case they ever went to an electric dryer. He agreed and allowed the taped red wire, unfortunately now we need 4 wires... hahaha
 
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