My friend’s new 220V dryer has the 4-prong plug, but her recepticle is the 3-prong type. I respect all eletricity, especially 220V. I offered to change the cord, as long as I’m positive it’s correct. I know how to wire the dryer terminal block, 2 hots on the outsides and the neutral in the middle. My question is, do I also have to run a jumper wire from neutral to ground? No one yet has been willing to advise me on this, rightly so given that 220V can kill, but I promise all of you that I will not go forward with this task unless I am 100% sure that I’m doing it correctly after reading any and all input anyone is willing to give. Thanks- John
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The dryer probably came with instructions on how to wire it for a three slot 220v outlet.
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The dryer probably came with instructions on how to wire it for a three slot 220v outlet.
It probably did, but my friend didn't get the directions with the dryer and I can't get them on line.
Why don't you change the recpetical and the wiring to the distribution panel?
If you know why that extra prong is on the plug, you know why you should do it right.
If you don't, hire an electrician.
Dave
I thought the neutral and the equipment ground met each other back at the panel box? (used same bus bar?)
I thought the neutral and the equipment ground met each other back at the panel box? (used same bus bar?)
This was wired with a 4 wire cord, the ground wire went to a screw on the metal body. I can't see for sure if the neutral bus bar is otherwise grounded... would it be...?
John, as simply stated as possible.
The neutral is a current carrying conductor.
The ground is a wire is a safe path to ground for any fault currents that may energize the appliance cabinet.
Why would you want to make the cabinet a potential part of the current carrying circuit by jumpering the ground to it at the appliance?
If you do not want to change the wiring back to the panel, tell us more about the receptical and wiring you can see. There may be other solutions to the ground issue.
Dave
Just wanted correct a misconception most people have about what a "neutral" is.
The white conductor in a 120 volt standard AC circuit is a current carrying conductor and is actually called the grounded conductor. This refers to the fact that it is terminated to the same buss bar with the system ground conductor at the main panel serving a location. The fact that this white conductor is a path for current flow means that it is NOT a neutral. Everyone calls it this but it's a contradiction!!!!
To have a neutral, you need a 240 volt circuit with two conductors at 120 V each. These 2 black conductors are in different phases so that when connected to a heating coil, motor, etc. they each serve as a return path for the flow of current. Only in this situation is the white (grounded) wire truly a "Neutral". The cabinet of dryers would be connected to the neutral with a jumper, usually at the 3 position terminal block to provide a path of least resistance for stray electricity that may energize the appliance cabinet via a frayed wire (black) coming in contact with it.
This was a better situation than no ground return path but is not as good as the changed code that requires a 4 wire connection which gives a separate groung conductor back to the panel. Often, it was recomended to ground appliances to a cold water pipe serving the utility room to provide an even better ground return path.
Hope this didn't sound too much like a lecture. Just wanted to be of help.......
"Often, it was recomended to ground appliances to a cold water pipe serving the utility room to provide an even better ground return path."
But that is against the code unless the water pipe meets the requiresment for a ground electrode.
To have a neutral, you need a 240 volt circuit with two conductors at 120 V each. These 2 black conductors are in different phases so that when connected to a heating coil, motor, etc. they each serve as a return path for the flow of current. Only in this situation is the white (grounded) wire truly a "Neutral". The cabinet of dryers would be connected to the neutral with a jumper, usually at the 3 position terminal block to provide a path of least resistance for stray electricity that may energize the appliance cabinet via a frayed wire (black) coming in contact with it.
So, in this case, the white wire can indeed be the ground as well, right? I would run a jumper from the ground screw to the middle (white) terminal? (and it didn’t sound like a lecture, even though I could use a few lectures on wiring… I’m always willing and eager to learn…)
Thanks Dave
In answer to your question-yes, jumper the cabinet to the white (grounded) conductor which is most often the middle terminal on the 3 position block at the back of the cabinet. This will provide a suitable if not perfect path for stray electricity to find its way to earth without sending most of it through your body should the cabinet become energized!!! You might want to mark the cabinet that this machine has been converted to a 3 wire type of system with the jumper added to the neutral. It should be disconnected if the dryer is moved to a house with the 4 wire type branch circuit. You will be changing the cord back to the 4 wire newer style to do this of course. The reason you will want it disconnected is to avoid having two separate ground paths which easily could have different potentials, thus providing the possibility of current flow between them.
My 1999 NEC code book shows that this was the year that they changed from the 3 wire to the 4 wire (separate grounding) requirement for ranges and dryers. See 250-140 . This section states that existing branch circuits could be 3 wire if the grounded (white) conductor is minimum #10 copper or #8 aluminum, the grounded conductor is either insulated or type SE (service entrance) wire originating at the service equipment. This is permitted for supply circuits of 120/240 volt single phase 3 wire or 208Y/120 Volt circuits derived from a 3-phase, 4-wire wye-connected system. Also there is a fourth requirement that grounding contacts of receptacles furnished as part of the equipment are bonded to the equipment. I assume this is mostly for ranges with the separate 120 volt receptacles for a coffee pot etc.
I did exactly as you said and it worked perfectly. Thanks again for all your help. John
Why would you want to make the cabinet a potential part of the current carrying circuit by jumpering the ground to it at the appliance?
Because, I believe that’s the way the dryer was originally wired (a stamp on the dryer reads; “3 wire 120V/240V 60 Hz 28 amp clothes dryer”). That’s why I think it was converted to a 4-wire by the last owner. I want to convert it back to a 3-wire. The reason I think this is possible comes, in part, from reading an article in FHB#153, pg 22 in Questions & Answers, about this. But my question remains, would you always add a jumper back to the ground screw in this situation…? And why do the dryer manufacturers lead you to believe that you can easily have either plug on the same dryer when people in the know seem to think it’s not that simple…?
If you do not want to change the wiring back to the panel, tell us more about the receptacle and wiring you can see. There may be other solutions to the ground issue.
I can’t change the wiring back to the panel, again, out of my league and timeframe, so it’s back to the 3-prong plug if it is indeed possible…
Thanks Dave
That would be nice but is that really cost/benefit wise. If panel were right beside the receptacle it would not be bad but most would be a real cost, probably more than the drier.
How many reported cases of death and destruction because of the standard three wire hookup before the NFPA decided we should wire all houses like trailers? There is no requirement that I have heard of when replacing an appliance in an existing three wire application to retrofit to four wire.
I am surprised that they waited this long to change it, but I belief that a number of locals changed it long ago.
But the code does specifically allow for the continued use of the 3 wire system and even with replacement driers.
If the receptacle is uses conduit or BX then it can be replaced a 4 wire receptacle. For upgrading to grounded receptacles the code specifically allows for an independent ground wire to be run. At least for 120 volt recpt, but I would have to check the wording to see if it could be used in this case.
The trickly part is that it has to be run back to the pannel or another device that is grounded, but in this case it has to be #10 wire and it might be just as difficult to do as to run a new cable.
But look on the back of the drier. There should be a label with a circuit, a label by the connections, or even stamped into the metal the information need to convert to 3 wire.
There will be a bonding jump, strap, or screw that will go from the metal case to the neutral terminal.
But look on the back of the drier. There should be a label with a circuit, a label by the connections, or even stamped into the metal the information need to convert to 3 wire.
There is, what I see is what told me it was a 3-wire to begin with, and was converted to 4-wire by the previous owner. The stamp reads “3 wire 120V/240V 60 Hz 28 amp clothes dryer.”
There will be a bonding jump, strap, or screw that will go from the metal case to the neutral terminal.
I think there was one, when it was originally a 3-prong plug, and that’s my original question, do I add a jumper back to that screw?
Thanks Bill
I am assuming that you have either terminal strip with screws or studs with 3 connection for the 2 hots and the neutral.
Then there is a place either a stud with a nut or a screws that is tapped right into the metal case and the green ground wire is connected to that.
If that is the case then you want to put in a jump from the ground terminal to the neutral one and then connect the 3 wire cable to the hot and neutral terminals.
Also you might take the brand and model number and do a google to see if you can find the insallation info or user's manual. Also alot of the appliance companies have 800 "customer care" numbers that might be able to supply the details.
Yes to your first two assumptions, thank you.
As for the 800 number, I've tried and I'll get more luck tomorrow. On line was no luck with the manufacturer.
Thanks again for you help.
My friends new dryer......,
Led me to think this was a new dryer, not a "new/used" dryer. Follow Bills' advice.
220v dryers are seldom just that voltage alone. The 220 volt is for the heating elements, and correctly stated, does not need a nuetral.
The drum motor and control wiring to the timer, etc. is generally 120v. That is one leg of the 220v lines and a white, neutral, wire.
For those here that advise using the nuetral as a ground. Read the volt/amps on the nuetral to a good ground when the machine is running! While it will not be 120v or very high amperage, it will clearly be something. The neutral wire is a current carrying conductor! Read the "feel lucky" thread .
Dave
I appologize to all, by "new dryer", I meant new to her, but it's 5 or 6 years old. Sorry to mislead from the very beginning.
My concern for connecting the ground to the neutral came from this forum and FHB comments stating exactly what you said Dave about nuetral carrying current, and , as pointed out in the "feel lucky" thread, one amp can kill you.
Thanks- John
Even new, new appliances come with the option to be used either way. Just too many existing 3 wire drier and range connections out there. I believe that it was just in 96 that the code was changed.
But I wonder how it has lasted that long.
But it is probably a relatively low risk, compared with all other potential electrical problems. Once installed and working it is not plugged and unplugs and the the sockets are beefy enough and the with #10 wire and good screw clamps there is relatively low probabilty that that the neutral will be lost.
Last year I did a bunch of work on my friens "new" house. It was built in 1950's and it appeared to have very good electrical for the time, but then there where a couple of remodels and an additon and the electrical system "suffered".
Among other things it had a 3 wire service for a sub-pannel for the addition (I wonder if that was code at the time 1970's, I have seen other older sub-pannels like that), but I know that the lack of connectors on the romex, 30 amp breakers on #14 circuits and much more where not code.
Aslo the HO was going with an electric range (the gas system has similar "issues) so a whole new 200 amp service was needed. I knew if I tried it that the house would be without power for 2 weeks So an electrican was brought in to do the new service and install the range circuit while I worked on other problems.
This was a brand new range. Now I was too busy to watch all of the details of what the electrican was doing, but everything that I saw, from the new ground rod, to labeling all of the circuits, to converting the sub-pannel to isolated ground, to routing the wiring in the CB pannel I did not have any hints that he was doing anything less and a 100% job and was up on everything.
But when he went to hook up the range he said well this has electronics (just a digital clock) and he had "heard" that the neutral shoudl be grounded. I lightly protested, but he ended up connect the 4 wire cord set to the ground, neutral, and 2 hots, but left the grounding strap in place.
So as soon as he left I redid it.
I agree with all you pointed out about the older three wire connections.
I wish someone at NFPA or NEC would give some good sound reasoning for some of the code changes.....i.e. arch fault circuit interupters. I found the best explanation for that one at Square D web site, although a little biased.
I think it best when trying to help others here to stay with the strictest interprtation of the code. That is why I am so quick to point out that the neutral is a conductor, in addition to having been zinged once or twice by a nuetral.
Dave
The realy strange thing about this is that on the 3 wire system the 3rd wire has to be a designated Neutral (white) wire unless SE cable is used then it is a ground wire (bare).
Now my 1979 house was wired with NM, so it is the ground wire. Does not meet the letter of the code, but is just as safe/unsafe as if SE was used. I bet that is a very common way of doing it.
Thanks to everyone for your help. We added the jumper, wired on the three-prong plug, and she runs like a top. And live customer service at Sears was a dead end as I feared, so thanks again to all for your help. John
"And live customer service at Sears was a dead end as I feared"
I was thinking of a someone like GE or Maytag when I suggested contacting them.
Glad I could be of help.
If it was a Sears housebrand I would bet on Whirlpool.
Bill, et al.,
The 1940 NEC included a change that allowed the use of the grounded conductor of a 240/120V circuit (the "neutral") as the equipment grounding conductor for clothes dryers and ranges. This was allowed because the war effort needed the copper. And the U.S. economy was on a full war footing by 1940, though the U.S. hadn't entered as a combatant. Shell casings, brass & bronze for ships, wiring for machines of war--all needed a lot of copper.
A dedicated run like a dryer or a range branch circuit is different from a general lighting branch circuit. If the terminals of the dryer or range circuit are made up properly, the chance of the neutral coming loose or otherwise being compromised is very low. Consequently, the chance of a simultaneous fault to the appliance case and the loss or impairment of the neutral was considered to be so small that it was acceptable. Compare that to a general lighting and convenience outlet circuit--maybe a dozen or more splices in the neutral, many made by the receptacle terminals.
I think it's better that the Code now requires separate equipment grounding and grounded conductors. But I can see why it was done.
Cliff
Have you seen a pre-1940 NEC to see if they did require an separate equipment ground. I have heard that explaination before.
But, to me it sounds too much like an "urban legend". Two reasons, first equipment grounds where not used for any other household equipment why ranges require one? And Second how much copper went into that one wire for that one circuit?
A while back I was in the local hardware store. Guy had a dryer recptacle in his hand and was talking to the clerk. Don't remember what he was asking. But after the clerk left I asked him what he was trying to do.
His daughter moved into a NEW, new house and her drier would not plug in. He wanted to change out the 14-30 (4 wire receptacle) and replace with with the older 3 wire.
I went and handed him a new 4 wire cord set. Explained how he need to install it on the drier. Even tried to explain the difference on the a paper sach using the little pencils on a string for selling bulks screws and nuts.
No response, just repeated the that 4 wire was the "new" and safter way of doing thing and to DO IT.
But as I left the store he still has the 3 wire recptacle in his hand and I am sure someplace in Eastern Jacomo that there is a laundry room with 4 wire cable connected to a 3 wire drier receptacle.
Why don't you change the recpetical and the wiring to the distribution panel?
That's out of my league and out of my timeframe, already spent 8 hours getting to this point for her, but that's another story.
As for the extra prong, I thought both 3 and 4 prong plugs were grounded, just done differently, hence the possible jumper wire.
And I wish she had hired an electrician, but stupid me offered... she's my old highschool sweetheart, how could I say no...?