Is a 10-2 conducutor acceptable for a Clothes Dryer?

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Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
Code section 250.118 Types of Equipment Grounding Conductors list MC as #10 on the list along with EMT, Rigid, Flexible metallic, etc... Just as an informational topic because I did run MC and all conductors are insulated in theory would I be code compliant if the equipment grounding conductor was re-identified with white tape and used as the nuetral conductor? This is merely a hypothetical question and i'm not going to embarass myself any further by asking AHJ if this will fly.

All MC cable is not listed for grounding. The run of the mill type with the aluminum sheath is not. ie":MC Lite by Southwire. It does not have the metal tape in it like AC cable does.
 

ceb58

Senior Member
Location
Raeford, NC
Code section 250.118 Types of Equipment Grounding Conductors list MC as #10 on the list along with EMT, Rigid, Flexible metallic, etc... Just as an informational topic because I did run MC and all conductors are insulated in theory would I be code compliant if the equipment grounding conductor was re-identified with white tape and used as the nuetral conductor? This is merely a hypothetical question and i'm not going to embarass myself any further by asking AHJ if this will fly.

Unless you have the speck. sheet stating
The metallic sheath or the combined metallicsheath and equipment grounding conductors of thesmooth or corrugated tube-type MC cable that islisted and identified as an equipment grounding​
conductor
The only one I am familiar with would be HC (Health Care) MC cable
...in addition to 250.118 does code section 250.134 Equipment Fastened in Place or connected by Permanent Wiring Methods (Fixed) - Grounding pertain to this situation?

I don't see a dryer meeting 250.134 try 250.138
 

goldstar

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
I've seen a lot of 3 prong clothes dryer receptacles. 240V with an equipment ground, I guess my inexperience led me to believe I had a choice between a 3 wire and a 2 wire.
Manufacturers can make this real simple. Run the dryer motor and heater on 240 VAC and if you need to operate your digital displays on 120 VAC install a small transformer in the PC board and re-manufacture whatever voltage you need. That way we we can cut our cost and the cost to the customer down and run 10/2. But, then again mfr's are interested in sales, sales, sales. Why should they care if it costs more for the customer on the back end.
 

kwired

Electron manager
Location
NE Nebraska
Manufacturers can make this real simple. Run the dryer motor and heater on 240 VAC and if you need to operate your digital displays on 120 VAC install a small transformer in the PC board and re-manufacture whatever voltage you need. That way we we can cut our cost and the cost to the customer down and run 10/2. But, then again mfr's are interested in sales, sales, sales. Why should they care if it costs more for the customer on the back end.
The standard of needing a neutral was set many years ago. outside of making everything operate at 240 volts, why would they want to increase costs by adding a transformer when the premesis wiring will include a neutral because they typically always do?

I have not seen a dryer that did not require a neutral, but would not be suprised if I did see one. People install circuits with a neutral anyway for ranges and dryers because the next replacement appliance may require a neutral.

Using the equipment grounding conductor for a neutral was never allowed.

Using the grounded neutral conductor for equipment grounding was allowed, and still is for existing installations where it was once acceptable.

Makes sense yet it doesn't, right?
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
All dryers come ready to run on a 10-2 wo/g. And this is where the big box store installers and electricians screw up.

They show up on a new 10-3 w/g and put the white and green leads on the center lug and never remove the 'bonding strap'.
 

iwire

Moderator
Staff member
Location
Massachusetts
In my opinion 10/2 NM has never been code compliant to supply a dryer.

A 3 wire dryer requires 2 hots and a neutral, all must be insulated.

The neutral was (is) allowed to be used as the grounding means, not the other way around.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Manufacturers can make this real simple. Run the dryer motor and heater on 240 VAC and if you need to operate your digital displays on 120 VAC install a small transformer in the PC board and re-manufacture whatever voltage you need. That way we we can cut our cost and the cost to the customer down and run 10/2. But, then again mfr's are interested in sales, sales, sales. Why should they care if it costs more for the customer on the back end.

I have hooked up a few dryers that only required 240V. However I still ran a 10/3 with ground to cover future installs. I have also wired a 240V washer in a residence.
 

iwire

Moderator
Staff member
Location
Massachusetts
Manufacturers can make this real simple. Run the dryer motor and heater on 240 VAC and if you need to operate your digital displays on 120 VAC install a small transformer

My understanding is that this is not a desirable way to go as they are designing the units to work as well with 208 volt service (as found in many apartments and city homes) as well as 240 volt homes.
 

kwired

Electron manager
Location
NE Nebraska
All dryers come ready to run on a 10-2 wo/g. And this is where the big box store installers and electricians screw up.

They show up on a new 10-3 w/g and put the white and green leads on the center lug and never remove the 'bonding strap'.

You sure you mean what you said. Isn't 10-2 wo/g two hots and nothing else? And probably a little difficult to find new anyway.

We have suppliers that stock 12-2 no ground UF cable on 2800 foot reels - but that is because there is a need for it for a control circuit for irrigation equipment. (Think kill wire or interlock for a well feeding a center pivot located 1/2 mile away from the well and only operating at 12VDC) Extra 2800 feet of one more conductor makes a difference in price if that conductor is not needed.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
You sure you mean what you said. Isn't 10-2 wo/g two hots and nothing else? And probably a little difficult to find new anyway.

We have suppliers that stock 12-2 no ground UF cable on 2800 foot reels - but that is because there is a need for it for a control circuit for irrigation equipment. (Think kill wire or interlock for a well feeding a center pivot located 1/2 mile away from the well and only operating at 12VDC) Extra 2800 feet of one more conductor makes a difference in price if that conductor is not needed.

Yes I posted 10-2 w/g incorrectly. TY.
 

templdl

Senior Member
Location
Wisconsin
If memory serves, 10/2 was never legal.

I believe that the OP reference to 10/2 omitted to state that there was also a grounding conductor.
Didn't they used to allow 10/2 w/grd where the grd double as a neutral years ago until someone saw the light and decided that it wasn't such a good idea? They did the same with range installation.
 

iwire

Moderator
Staff member
Location
Massachusetts
I believe that the OP reference to 10/2 omitted to state that there was also a grounding conductor.
Didn't they used to allow 10/2 w/grd where the grd double as a neutral years ago until someone saw the light and decided that it wasn't such a good idea? They did the same with range installation.

No

For many years we were allowed to use the neutral to ground dryers and ranges.

Being a neutral and in NM it is required to be insulated, that forces us to use 10/3 and abandon the bare EGC.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I thing there are 2 issues here. The op is talking about MC cable. So 10/2 MC has an insulated grounding conductor and would have been compliant years ago if the green wire could be compliantly taped white. Even as a green conductor it would function perfectly well back in the days of 3 wire dryers but again technically not compliant.

As a 10/2 NM cable-- that was never compliant. Not sure why since 10/2 seu cable was compliant if the circuit originated from a main panel.
 

templdl

Senior Member
Location
Wisconsin
No

For many years we were allowed to use the neutral to ground dryers and ranges.

Being a neutral and in NM it is required to be insulated, that forces us to use 10/3 and abandon the bare EGC.

As such understand that the 'no' means that ther is n grounding conductor.

And for as many years I have always wondered why the neutral was allowed to share the grounding conductor. Doing so makes it possible for the neutral current to be let loose on the appliance itself. Should that grounding conductor become compromised then the appliance is not longer grounded providing you with the privilage of getting an electric shock if you were unfortunate to come into contact with the appliance. That's probably why the appliance was often bonded to the water pipe with the ground provisions of the appliance and a ground screw clamped to the water pipe as a safety net.
 

kwired

Electron manager
Location
NE Nebraska
No

For many years we were allowed to use the neutral to ground dryers and ranges.

Being a neutral and in NM it is required to be insulated, that forces us to use 10/3 and abandon the bare EGC.

The Bare outer conductor in SE cable was allowed to be used though, don't really know why that was any different but that is the way it was - and still is where the exception for three wire circuit applies.

As such understand that the 'no' means that ther is n grounding conductor.

And for as many years I have always wondered why the neutral was allowed to share the grounding conductor. Doing so makes it possible for the neutral current to be let loose on the appliance itself. Should that grounding conductor become compromised then the appliance is not longer grounded providing you with the privilage of getting an electric shock if you were unfortunate to come into contact with the appliance. That's probably why the appliance was often bonded to the water pipe with the ground provisions of the appliance and a ground screw clamped to the water pipe as a safety net.

Best explanation I have heard, yet it's validitiy has been shot down before, is that it was for conserving copper back during World War II times, this condition only applied to electric ranges and clothes dryers. Pretty much all other branch circuits were required to have separate neutral and equipment grounding conductors when and where equipment grounding conductors were required, it was not until sometime in 1960's or so that equipment grounding conductor was required for pretty much every branch circuit.

If it is true that this rule started for that reasonand at that time I wonder why it took 50-60 years to get it changed to be consistant with the grounding rules for everything else, other than there probably was no significant number of bad instances involving that type of installation.
 

jxofaltrds

Inspector Mike®
Location
Mike P. Columbus Ohio
Occupation
ESI, PI, RBO
Non-engineer here. Does the range need a 'neutral'?

Didn't we use to just run H-H-G (black,white,bare) to dryers and ranges? It's been so long I don't remember!
 

templdl

Senior Member
Location
Wisconsin
If it is true that this rule started for that reasonand at that time I wonder why it took 50-60 years to get it changed to be consistant with the grounding rules for everything else, other than there probably was no significant number of bad instances involving that type of installation.

That what is so strange as there hasn't been a significate number of instances. That may be the reason that it has taken so long to revise the code.
 

kwired

Electron manager
Location
NE Nebraska
Non-engineer here. Does the range need a 'neutral'?

Didn't we use to just run H-H-G (black,white,bare) to dryers and ranges? It's been so long I don't remember!

There has been ranges and dryers that have neutral loads for long time. Ranges usually had at very least a 120 volt oven light, and maybe a 120 volt timer or clock. Dryers almost always have had 120 volt motor and 120 volt control timer, and sometimes a 120 volt light inside the drum. When you do run into one of these appliances with no neutral load they still have a neutral terminal on the main power block - I suppose partly because most of them will still have a 125/250 volt cord cap installed on them and that gives you a place to land the neutral even though it isn't needed.
 
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