Washing machine crapped out this week. Nothing seemed amiss, so I grabbed the old multi-meter & checked the outlet. 120 jolts to ground, but nothing to neutral. Surmised a brokrn neutral connection somewhere.
Rooted around in the box of spaghetti called the service panel, checking tightness of all the neutral connections on the buss bar. (That was the easiest thing to check, so did it first.) Lo & behold, found the neutral for the ckt was quite burned & very loose in its hole. Cut off about 4 inches of wire & moved it to the top of the buss bar. Retightened it & all is fine.
Now for the Gotcha! My daughter & I ran all the wires for the house, but I hired a real, licensed electrician to put together the service panel. After he finished, having read a ton of stuff here about the hazards of loose neutrals, I went down the buss & checked every screw. None were loose. About 8 mo ago, added the required AFCI in the bedroom ckts & immediately had som random dimming of lights. Went & checked al the neutrals again & found a few that were loose. Now, two yrs plus down the pike, this happens. Checked all the neutrals again & was able to add a wee bit of torque to about half of the screws. I’m afraid to add much more torque for fear of crushing the soft copper wires.
Why? It’s solid copper wire.
Don
The Glass Masterworks
“If it scratches, I etch it!”
Replies
Don,
Any chance that this is a multi-wire circuit (i.e., two circuits that share a neutral)? The two MW circuits have to come off of opposite poles or legs of the service, or the neutral will carry the SUM of the currents and not the difference (as when wired correctly). That'll burn a neutral pretty quick.
If thats not the case, on the neutral bus bar, is there only one neutral wire per terminal? If two, the expansion/contraction from normal current heating will loosen things up, and arcing ensues. That'll burn a neutral.
Some guys think it's overkill, but I use a torque screwdrive to tighten the terminal screws in the panel (and the breaker terminal screws as well). Not that it can't be done by feel, but once I've torqued those puppies to the mfgrs specs, I don't have to worry about a situation like yours.
It's suprising how much torque the specs call for (typically 25-30 inch-oz for a terminal screw for up to AWG10 wire). More than I'd do by feel. Of course, I have a friend who installed a service panel and really cranked down on the neutral/ground terminal screws. It was one of those "cage" style terminal bars. As he tightened the last screw, the terminal bar split apart. He was "gorilla Bob" after that.
As far as re-tightening the terminal screws, the industry convention is to not re-torque a terminal, for the very reason you mention--deforming the conductor or even cutting it off. The "by-the-book" way is to cut off the old wire and tighten the terminal on "fresh" wire.
BTW, nice work on the troubleshooting.
Cliff
Cliff: I assume that you are the famous author, Cliff Popejoy. I cannot take full credit for all the troubleshooting. I made the basic diagnosis, but asked an electrician-tuirned-glass-artist friend for advice on the simplest way to track it down.It is not a MW pair of ckts. There are a bunch of connections where there are two wires under the same screw. You are correct - they seemed to be guilty of being "Loose" more frequently than any of the single wire connections.I saw the criterion for torque - 25 in-oz, & figured that it could not be a whole lot of torque. I am used to torques in the ft-lb range, and Have a decent feel for when things are too tight. I fear crushing copper & aluminum, so I am careful.Looks like I have a job in the future for my spare time - removing all the neutrals & cutting ther ends off & reinserting them. I'll get a torque screwdriver for this effort. I at least have some vacant holes in the Buss, so I can move them all up one or two slots when I shorten them. I will also reduce the two wire connections.My daughter is a budding surgeon, who started out as an EE. I've had several electricians complimen her on the neatness of her job. She also troubleshot a bad light fixture in a closet, going right to the offending connection in the attic. She is considerably smaller than I am, & was ideally suited to running the wires through the attic spaces. She said that it was more like crawling wires than running them.Thanks.DonDon Reinhard
The Glass Masterworks
"If it scratches, I etch it!"
Don,
You're welcome. Yes, I'm the one who's written a few articles for the magazine.
Well, working in that panel, re-making the connections, will keep you out of trouble! I'd cut power to the panel (if you weren't planning to already). It's too easy to get lax when you've got your hands in a panel for an hour or two. I once fried a torque driver working in a hot panel, and it was a real sobering experience. By some miracle, I wasn't injured.
Anyway, there's no reason to keep the power on (no one in the house is on life support, right?)
Best to your daughter, congrats on her successes both electrical and medical. Maybe a career as a neurosurgeon, and combine the two fields?
Cliff
Cliff, have you got a source for the torque screwdriver?
I have checked every supply house in my area. All I get a blank look when I ask.
Dave
Speaking of this subject, I have a customer putting in a new kitchen that is ready for his new electric range..I go to install the 4-wire cord and a new 50 amp receptacle and find there is no neutral in the box...just two awg 8 conductors and a frazzled, braided ground wire inside. Looked at the old range he'd pulled out and saw they'd just wire-nutted the neutral to the ground and tied the whole thing to the braided ground back to the panel. SO he'd had a bare copper acting as his neutral conductor for his 240/120 range. I told him he needed another (insulated) conductor ran back to the panel for the neutral and I wasn't hooking it up the "way it was".Question is: yea, it seemed to work fine for the old stove. But how dangerous was it? And what specifically was the danger?
That sort of hookup used to be legal, more or less. The rule changed in the 70s, I believe.
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No electrons were harmed in the making of this post.
3-wire range and dryer connections where legal until 1993 (or was it 96) in most cases. Mobile homes, connections from sub-panels, and some city required 4 wire connections.And it is still legal to connect new equipment to exessing 3 -wire supplies. It would be up the the AHJ to tell if the adding a receptacle would be require that the circuit be updated or not.All ranges and dryers that I have seen have the connections and labels on the back how to connect them for both 3 wire and 4 wire installations.For 3 wire the metal case of the appliance is bonded to the neutral and the neutral serves as the equipment grounding conductor.That is not the best system in the world, but apparently it is not that dangerous it is still allowed for connecting new appliacne installations.
Bill, are we talking about the same thing? This fixture had no NEUTRAL at all..only two hots and a bare ground..the old range was using the ground as a neutral, not visa versa..The new range definetly needs a neutral conductor to run the 120v portions of the appliance (timers, lights, etc.). You're not saying it's (or was) kosher to use a ground as a neutral conductor, are you?
It was.--------------
No electrons were harmed in the making of this post.
This is kinda of technical, but here is what the code says."Frames of ... clothes dryers ... shall be permitted to be GROUNDED to the GROUNDED CIRCUIT CONDUCTOR if all of the following conditions are met....(3) The GROUNDED CONDUCTR is insulated or the GROUNDED CONDUCTOR is uninsulated and part of a Type SE service entrance cable and the bre branch circuit oringinates at the serice equipment."...The GROUNDED CONDUCTOR is codeze for Neutral. What is commonly called "the ground" is the Equipment Grounding Conductor, EGC.There are several different styles of types of SE cables. But one common one has 2 hot conductors and they are wrapped with a spiralled bare GROUNDING CONDUCTOR or neutral.Now if this is NM (Romex)(with a bare ground) then it is not properly wired. But it has been know to happen. If it was older NM, before grounds, then you would have 3 insulated conductors and it would be OK.
Edited 10/28/2005 12:20 am by BillHartmann
Gotcha.. Thanks for clarifying.
Tool supply house like Tech Tools and Jensen have themhttp://www.tek-tools.comhttp://www.jensentools.com/But they are full of asembly tools so it might be hard to find the basic torque screwdriver.
Thanks Bill
> have you got a source for the torque screwdriver?
Another good place to try: http://www.fastenal.com
-- J.S.
This reminds of something I ran into last summer.I have done a bunch of "handyman" repair work on a house (replaced burned out lights, dimmers, photocells, leaking toilets, broken DG, etc).Got a call that the dryer was not heating, but it was running and that I should check it out to see if a service man is needed. (One of my other "fixes" was the washing maching - apparently he had gotten a phone call or something that districted him and he had pulled out the switch in the middel of a cycle and forget it and came home latter and found the washer in mid-cycle and full of water).So I check the breakers and found that 1/2 tripped (2 pole Zinsco with a tie-bar between sections). Reset it and removed the lint from the filter (don't know if it had every been clean) and the dry was find.About 6 weeks later same problem.So this time I had a clamp on amp meter. Checked the one leg and it was right on.Pulled the wire out a little on the other leg to get the probe around and the wire just comes out. The terminal screw on the breaker was down tight. Best I can tell that for 25 years that wire was just pushed up against the terminal on the breaker.Put it UNDER the terminal and it has been OK for the last 4 months.
In a thread in the WoodNet forums there was a discussion about 3/4 wire dryer connections.MattM, an electrican, posted this comment;"The topic in this thread can be a tough one. Why was a 3-wire dryer or range installation legal for years, and now suddenly its not. Its kind of like Cheech and Chong talking to their children about the dangers of using drugs."
I figure why worry about it. I've got a bunch of loose neural connections and they don't seem to cause any problems.
Oh, NEUTRAL connections ... never mind.
No electrons were harmed in the making of this post.