3 wire dryer circuit

[phil kaznowski]

In the older style dryer circuit (2 hot/1 neutral) where does the neutral terminate at a sub panel? I am having a brain freeze.

Thanks,

Phil

[Bill Kriegh]

The fact it is a neutral should be a clue.

The rule is that a grounding conductor is never allowed to carry anything but fault current. The neutral (grounded conductor) carries part of the electrical load of the dryer and therefore has to be connected to the neutral buss. See 2008 NEC 250.142 (B) Exception 1

A common violation in sub panels (that there would be non service equipment for at least one guy here) is a bare neutral on a range or dryer circuit. The neutral has to be insulated - you can't have the bare concentric conductor found on type SE cable, for example. See 2008 NEC 250.140 Exception

[phil kaznowski]

Bill,

Thanks for the reply. The thing that threw me was that the circuit was single wire which at first glance made me second guess what I was actually looking at.

[Jerry Peck]

In a 3 wire 220 circuit, is the third wire always a neutral? Or can it be a grounding conductor in some installations? I'm thinking of a water heater as an example.

With a water heater, the third (white) wire is not used. You would use the black, the red, and the bare ground.

Your question started off more complex, but ended with "I'm thinking of a water heater as an example" so the answer is based on a water heater.

[Jim Port]

Not sure why someone would run a 3 wire + ground cable to a straight 240 volt equipment. Maybe they didn't know what they were doing or they had extra money to burn?

The common and code compliant method is to run a 2 wire + ground and re-identify the white as a hot conductor.

[Jerry Peck]

The common and code compliant method is to run a 2 wire + ground and re-identify the white as a hot conductor.

Jim,

That would be the logical way to do it, however, the common and code NON-compliant method of running 2 conductors plus a ground and NOT re-identifying the white as a hot conductor is really "the common" way it is done.

It is extremely rare ... extremely rare ... to find the white re-identified, permanently or otherwise.

Which is why it shows up so much in the photos posted here and in home inspector reports.

[Tony Mount]

Jerry, with your statement is Bill right or wrong?
With a water heater, the third (white) wire is not used. You would use the black, the red, and the bare ground.
The rule is that a grounding conductor is never allowed to carry anything but fault current. The neutral (grounded conductor) carries part of the electrical load of the dryer and therefore has to be connected to the neutral buss. See 2008 NEC 250.142 (B) Exception 1.......you can't have the bare concentric conductor found on type SE cable,

[Jerry Peck]

Jerry, with your statement is Bill right or wrong?

Bill was correct.

Why do you ask? I did not say anything about Bill being incorrect.

You, on the other hand, ...

you can't have the bare concentric conductor found on type SE cable,
... are incorrect in that statement.

You will need to go back and re-read what Bill wrote to find out why he is correct and you are not - it is all in what Bill stated, and what you did not state.

[Jerry Peck]

Jerry, reason I asked- I recently bought a new dryer. The wiring instructions show how to hook it up to a 3-wire or 4-wire receptacle but don't specify if the 3rd wire is neutral or ground.

Fritz,

*IF* (there is that big *IF*) ... if there is a ground present at the box where the plug is, the connection is required to be made with a 4-wire cord and plug set and receptacle, and there will be two hots, one neutral, and one ground.

On an older home, there will be one of two wiring configurations present:
- 1) Older home with circuit supplied from a not-service equipment panel in which there will be two hots and one neutral. Being as that not-service equipment panel (or simply "panel") has its neutral isolated from ground, the circuit to the dryer needs to have its neutral isolated from ground, i.e., "insulated". The third wire is then a "neutral.
- 2) Older home (or even older older home) supplied from a service equipment panel in which there will be two hots and one neutral. Being as that panel IS also service equipment, the neutral is also bonded to ground, thus the circuit to the dryer "could be" EITHER:
- - a) two hots and an UNinsulated neutral/grounding conductor (which is the UNinsulated outer conductor wrapped around two inner conductors in service entrance cable) - the third conductor is a "neutral/grounding" conductor as it comes from the service equipment (this is the wiring MOST OFTEN found in an older home, most often an older circuit, maybe original to the home)
- - b) two hots and an insulated neutral, and a ground where the third conductor would be connected to "neutral" and the ground connected to the cabinet - like in 1) above (this is seldom found in an older home, when found it is most often a new circuit installation in the older home)

[Jerry Peck]

Greetings! I live in the Philippines. Where I live uses 220 volts for everything.
Two black wires only, no neutral, and no ground.
I hooked up an American type dryer after the local installer tried to use a fifty cent lamp plug instead of the normal pigtail. Cant find one anywhere, it on order from the states.
I hooked the normal two black wires to the two hots, and installed a ground wire and connected it between the cabinet green and an extra telephone grounding ? ( cant remember the name for the big 8 feet long metal pole coming out of the ground) electrode ????.
IS IT SAFE? :confused: Don't worry about any code here.:p

Roger,

Sounds like you would have a grounded system if you have a 8 foot ground rod, and, with a grounded system (even 240 volts only) there should be a ground/grounding wire run with the system. Thus there would be no need to run that grounding wire back to the ground rod, when you install the cord and plug set it will have three prongs, as will the receptacle - two hots and one ground, and the green should go to that ground, and that ground from the receptacle should go to the ground on your wiring system run with the circuit conductors, which, yes, does make its way back to that ground rod ... but the way you did it is not the correct way to do it.

[John Steinke]

The older style 3-wire ranges and dryers didn't have a neutral ... they had grounds. They used the ground as their neutral.

In all fairness, the NEC only prohibits 'objectionable' current on the ground wire. There are numerous instances even today, where the electronic components in some devices continue to use the ground as a neutral.

Often lost in the debate is the fact that, using romex as the wiring method, there is no way for there to be multiple return paths. Therefore, none of the concerns voiced in advocating the code change (to requiring 4-prong plugs) apply. It's something to lose sleep over.

I'll edit to add: If you decide to use a GFI breaker, then the ground will have to be isolated, and treated like a neutral.

[Jerry Peck]

The older style 3-wire ranges and dryers didn't have a neutral ... they had grounds. They used the ground as their neutral.

Those were ONLY allowed when fed from a panel which was part of the service equipment.

Those were not allowed when fed from a panel which was not service equipment.

You will see that in the posts above by Jim, Bill, and myself, and (in other posts on other threads) Fred.

[Gerry Martin]

Howdy. Another issue is the connection at the appliance. In a 3 wire connection, the neutral is required to be bonded to the frame of the appliance, whereas in a 4 wire connection, the neutral is isolated from the frame. In this instance there is a 4th. (grounding) conductor which is connected to the frame. The dryer should have been factory equipped with a bonding strap to facilitate either type of connection. :D

[Bill Kriegh]

The older style 3-wire ranges and dryers didn't have a neutral ... they had grounds. They used the ground as their neutral.

I'm afraid I need to disagree. The wire present in these old circuits is the neutral. The fact the conductor needs to be insulated when connected to other than service equipment proves this out. The neutral conducror has always been required because of the design of the appliance.

"Objectionable" current on a ground is confined to "ground loops" that may cause problems, usually with electronic equipment. It has no bearing on the fact that the ground is NOT to be used as a current carrying conductor in any circumstances but a fault.

[Robert Mattison]

To: Phil Kaznowski; greetings. My name is Robert.

My reply to your question don't have a brain freeze while working
with electric power.


Bill, Gerry Jerry & John have given you all good answers.
But most D.I.Y. will never understand the NEC code box fully.
AND inspectors spend their life trying to makes sense of it.

And person can connects wires to an electrical panel and get the
lights to work.

Many people don't under understand how the service to your home
works.

Much electric stove and clothes dryer can work off the 3-wire circuit.
Using L1 (hot to ground) @ 120 volts. L2 (hot to ground) @ 120 vots
to ground. Measure across L1 AND L2 and you have 240 volts.

Electric stoves and electric clothes dryers don't care about how their
wired, get the proper voltage to them and they will performed their
job.

What does matter is the, NATIONAL AND STATE AND LOCAL ELEC-
TRICAL CODES, which for safety requires that you wire your electric
clothes dryers to their rules. If you don't could be criminal prose-
cute Or fined.

If your job as an inspector to see if the job is wired correctly.
By placing your question in this forum, means your care.

Now that you have the answers from the other guys, I suggest you
contact your local or state AHJ, THEY can also be helpful. If not write
back and I will give the answer for what the AHJ in my area requries.
Good Luck!

[Rollie Meyers]

A 3-wire feed was allowed to be fed from a subpanel, a 3-wire SE cable w/ a uninsulated neutral conductor was only allowed to be fed from service equipment.See 250.140(3) 2005 NEC. 250-60 in the 1996 NEC changed the rules in no longer allowing 3-wire in anything other then existing installations.

[Robert Mattison]

May 13, 2009

Nice post Rollie Meyers, I couldn't agree with you more. But feel free to
correct if I'm wrong.

1st. Phil Kaznowskie doen't say if there an existing circuit that he plans to
used. But your post with give food for thought. Thanks for bring it his
attention. Robert

[Robert Mattison]

May 13, 2009 Robert her again, sorry for my previous post with all the type-o mistakes. 8:22 P.M.

[Tom Edwards]

Is there an important difference in 240 appliance outlets?
I inspected a condo built in 1998 in NC and the dryer outlet has 3 vertical blades and one round prong, I assume to be the grounding conductor.
The client is being told by a GE appliance tech (bought a new dryer) that he must change the outlet installed at construction as it is intended for a range, not a dryer. He states that the outlet installed is a 250V outlet and he must install a 240V outlet.
My client is asking me whether this is neccessary and I am unable to speak to this with technical info and authority. I have not found any reference to this issue in the IRC. Did I miss something?
Any help is appreciated.

(I may have posted this same question in another thread. If you haven't answered the other thread I would appreciate your answering here. Thanks again.)

[Jerry Peck]

Is there an important difference in 240 appliance outlets?
I inspected a condo built in 1998 in NC and the dryer outlet has 3 vertical blades and one round prong, I assume to be the grounding conductor.
The client is being told by a GE appliance tech (bought a new dryer) that he must change the outlet installed at construction as it is intended for a range, not a dryer. He states that the outlet installed is a 250V outlet and he must install a 240V outlet.
My client is asking me whether this is neccessary and I am unable to speak to this with technical info and authority. I have not found any reference to this issue in the IRC. Did I miss something?
Any help is appreciated.

(I may have posted this same question in another thread. If you haven't answered the other thread I would appreciate your answering here. Thanks again.)

That installers is off his meds.

NEW DRYER circuits have four conductors: 2-hot, 1-neutral, and 1-ground.

OLDER dryer circuits have three conductors: 2-hots, 1-neutral/ground.

Clothes dryers are manufactured and designed to be adaptable to either circuit, the difference is the cord and the connection at the dryer end.

There is no need to change the receptacle, NOTHING will be gained, that installer needs to install a dryer cord with 3-prongs.

My guess is that the installer ONLY brought 4-prong dryer cords with him, and could not install the dryer, so the excuse for their incompetence of knowing about the two types of installations for older dryers and newer dryers and not carrying both types of cords was ... need to change the receptacle.

That installer is only doing what he was trained to do, which is from lack of training, otherwise he would have recognized that there is no benefit from changing the receptacle - he would have had to re-wire the circuit too.

Give the installer an 'A' for doing what he was trained to do, give him a 'F' for not knowing what he should do, and give his trainer an 'F' for improper training.

[Tom Edwards]

the dryer outlet has 3 vertical blades and one round prong, I assume to be the grounding conductor.
The client is being told by a GE appliance tech (bought a new dryer) that he must change the outlet installed at construction as it is intended for a range, not a dryer. He states that the outlet installed is a 250V outlet and he must install a 240V outlet.


I may not have been clear, Jerry.
The outlet has 4 prongs as it was built in 1998.
The question is whether the outlet is designed and acceptable for a dryer. The GE tech states that the installed outlet is intended for a range only.
It's all about the blade configuration and whether different outlet design (all four prong) are different to meet different requirements between the two different appliances.
Thanks for answering.

[Jerry Peck]

I may not have been clear, Jerry.
The outlet has 4 prongs as it was built in 1998.
The question is whether the outlet is designed and acceptable for a dryer. The GE tech states that the installed outlet is intended for a range only.

Okay, I follow you now, I thought you were talking about 3-prong receptacles. Got it now.

Both the dryer receptacle and range receptacle (talking about 4 prong receptacles here) have the same voltage rating.

The difference is that the clothes dryer receptacle configuration rating is only 30 amps while the range configuration rating is 50 amps.

He could install a range cord on the dryer and use that receptacle, but would need to make sure the breaker was only 30 amps.

Or he could replace the receptacle with a 30 amp rated one to match the dryer cord and plug, BUT WOULD STILL need to make sure the breaker was only 30 amps.

I would recommend replacing the receptacle and making sure it was only a 30 amp breaker.

[ken horak]

......

[ken horak]

a 50 amp receptacle is not allowed on a 30 amp circuit. So using a range
cord and the range recptacle is incorrect even if the breaker is changed to a 30 amp.

[Jerry Peck]

a 50 amp receptacle is not allowed on a 30 amp circuit. So using a range
cord and the range recptacle is incorrect even if the breaker is changed to a 30 amp.

Ken,

Please explain this to me.

(bold and underlining are mine)
- 210.21 Outlet Devices.
- - Outlet devices shall have an ampere rating that is not less than the load to be served and shall comply with 210.21(A) and (B).
- - - (A) Lampholders. Where connected to a branch circuit having a rating in excess of 20 amperes, lampholders shall be of the heavy-duty type. A heavy-duty lampholder shall have a rating of not less than 660 watts if of the admedium type, or not less than 750 watts if of any other type.
- - - (B) Receptacles.
- - - - (1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.
- - - - - Exception No. 1: A receptacle installed in accordance with 430.81(B).
- - - - - Exception No. 2: A receptacle installed exclusively for the use of a cord-and-plug-connected arc welder shall be permitted to have an ampere rating not less than the minimum branch-circuit conductor ampacity determined by 630.11(A) for arc welders.
- - - - - - FPN: See the definition of receptacle in Article 100.

Repeat:
- - - (B) Receptacles.
- - - - (1) Single Receptacle on an Individual Branch Circuit. A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit.

The circuit is 30 amps, the RECEPTACLE is 50 amps, the RECEPTACLE "shall have an ampere rating NOT LESS THAN that of the branch circuit".

Explain why you said "a 50 amp receptacle is not allowed on a 30 amp circuit".

[Tom Edwards]

The circuit is 30 amps, the RECEPTACLE is 50 amps, the RECEPTACLE "shall have an ampere rating NOT LESS THAN that of the branch circuit".
So, Jerry, the 50A, range-rated, outlet is in compliance with code and there is no reason regarding safety or non-compliance that anyone would need to replace the outlet if they could just as easily use a 50A appliance cord. Are the voltage ratings different between the two different outlets discussed here?

[Jerry Peck]

Are the voltage ratings different between the two different outlets discussed here?

Same voltage ratings.

[Tom Edwards]

Thanks.
The GE appliance tech is telling my client that a 50A range outlet, which is installed in all 12 units in this building, is rated at 250A and must be replaced with a dryer outlet at 30A/240V. Sounds like bunk to me.
You agree?

[John Kogel]

In fairness to everybody, the 50 amp receptacle will not accept a 30 amp dryer cord and vice versa because the pins are configured differently on purpose.
Changing the breaker and cord will make the dryer work, but down the road, someone might plug in a range and overload the 30 Amp breaker. I think that would be Ken's and probably the appliance installer's objection to doing that - it ain't right.

That other thing about 250 volts is indeed bunk. He's right about the wrong receptacles being used, just confused about electricity. I think?

[Tom Edwards]

Thanks, John.
This is an outlet in a laundry room in a condo with 12 units in the building all wired the same in Winston-Salem, NC.
I originally told them to simply use an appliance cord that met the outlet config but the appliance tech has them convinced that that will risk safety somehow in its operation as a dryer.
Thanks.

[Jerry Peck]

Thanks.
The GE appliance tech is telling my client that a 50A range outlet, which is installed in all 12 units in this building, is rated at 250A and must be replaced with a dryer outlet at 30A/240V. Sounds like bunk to me.
You agree?

Tom,

Go here: http://www.hubbellonline.com/wiring/bryant/pdf/b/b5.pdf

Scroll down to 3-pole 4-wire grounding.

Look at B-33/14-30P (clothes dryer plug) and B-33/14-50P (range plug), then go back to the left column and you will see both are rated 125/250V.

[Tom Edwards]

Outstanding, Jerry!
That, along with your earlier NEC references, which I looked up, clear the issue up for me.
Yes, the outlet installed in the inspected property is a 50A/250V device that is in compliance with the NEC.
If the appliance tech wants to change it he is using his own reasons that are unrelated to the NEC. Right!
Thanks very much for all the info.

[ken horak]

my bad

Just a bad idea then!

Just think you say to change breaker and use the 50 amp receptacle and cord set.
In a few years another HI will be there and see it. Then post the findings here.
Then you will will beat up on an electrician for not doing it right

[Jerry Peck]

Just a bad idea then!

Just think you say to change breaker and use the 50 amp receptacle and cord set.
In a few years another HI will be there and see it. Then post the findings here.
Then you will will beat up on an electrician for not doing it right


I completely agree, but then code is "minimum" isn't it? It pre-supposes that people working on the systems are "qualified" and we know they are not, many so called "qualified" people are not *qualified*, let alone home owners and the "handyman" working without a license and even less knowledge.