switch grounded outlet combo question.

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I have a single pole switch outlet combo device in my kitchen. The switch started to make a loud pop when the light was turned off, not on. I tried to replace the device and here is what happened. There are three wires in the box. I know the one hot and the other are neutral. No ground wire. I wired hot to hot, and the neutrals to the other two silver and then light brass screw. Powered on and the switch worked, no plug, unless switch was on. Reversed the two neutrals and now only outlet works, no switch. What did I do. There are two screws for the hot, one labeled common and the other unlabeled and they are both connected by a brass tab. Help. The previous combo was not grounded, two pronger, 10A. New is grounded 15A.
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Is this receptacle supposed to have one switched and one unswitched outlet? If so, there have to be two hots - one on all the time, the other controlled by the switch. They're both connected to the "hot" side of the outlet, but you have to break the tab.
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Go hire an electrician before you burn your house down or kill somebody. Seriously, you don't know what you're doing and you really could do some damage.
Why, exactly, would there be two neutrals? Hmmm? Maybe, just maybe, only ONE is a neutral and one is a lead from the light fixture you're wanting to control.
It sounds like the combo unit is set up so that the switch can control the outlet. There should be a tab between the top (switch) and outlet (bottom) on one side. For the switch to control the outlet you would just apply power to the side opposite the tab, preferably to the switch, then connect the neutral to the side of the outlet opposite the tab. Switch controls outlet.
It sounds like you want the outlet on all the time and the switch to control an (overhead?) light. Wire the hot lead to the side of the unit with the tab. This applies power to one side of the both the outlet and the switch. The neutral goes to the other side of the outlet. The wire from the overhead light goes to the other side of the switch. The switch is inline on the hot lead to the light, the outlet works all the time.
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Doesnt matter if the hot is on top or bottom, switch outlet respectively.? The multimeter read hot 120v and the other wire read 85-90v and then neutral. Why is one lower v?
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again, as you were told before, you don't know what you are doing. That's why you are getting the 80 some volt reading. (and the fact that you are using a digital VOM) right?
get someone over there that can do the job before you fry your hand.
s

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You really need to get a book on this at least, get an experienced friend to help, or as someone else suggested, call an electrician. It's hard to give you a sure answer without looking at how it's wired up, there's more than one way it may have been done. If uncertain, you really don't want to be messing with this stuff.
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The white wires are not neutrals (a neutral only occurs in a 240 volt circuit and carries the unbalanced load of the two legs.) And most likely, one or two of the white wires is what is called a switch leg, that is, it is actually a ungrounded (or black) wire run to the switch to be "switched". (But actually it's a "hot" wire in disguise).
As two others have told you, get someone knowledgeable as you could be very well setting up a shock hazard in your home. It's important that certain wires be isolated from the metal of the fixtures and appliances, others intentionally connected to ground, and only someone with experience can tell the difference.
What if someone were to be seriously shocked while changing a light bulb due to your inexperience? It's not worth the low cost of being safe.

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Neutral wires are present in 120V circuits as well, yes neutral and ground busses are bonded together in the panel, but the white wire is still called neutral though it carries the full return current. A white wire can be hot if used in a switch drop or to a 240v appliance receptacle but in that case there should be a band of black or red tape around it to mark it as such, though in most houses I've worked on they've skipped that.
Note that this assumes USA, I'm not as knowledgeable about the electrical codes in other countries.
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A lot of people refer to the white as a neutral, but offically in the NEC is referred to as an "identified" conductor.
A neutral is only present in a 240 v or higher branch circuit or feeder. (I think that's where a lot of confusion comes in as the potential between a 240 volt leg and the neutral is 120 volts, however that's not a branch circuit in and of itself). Because a neutral carries only an unbalanced load, it's allowed to be reduced in size from the ungrounded phase conductors. See 220.61 where the NEC talks about how to calculate the unbalanced load on a neutral. A grounded white wire in a 120 volt circuit always carries the full load of the circuit and is sized the same as an ungrounded conductor.
I pulled this off of Mike Holt's website (read carefully, the 2-wire circuit in the 2nd para is a standard 120 volt circuit): Neutral Conductor. The IEEE dictionary defines a neutral conductor as the conductor with an equal potential difference between it and
the other output conductors of a 3- or 4-wire system. Therefore, a neutral conductor is the white/gray wire of a 3-wire single-phase
120/240V system, or of a 4-wire three-phase 120/208V or 277/480V system.
Since a neutral conductor must have equal potential between it and all ungrounded conductors in a 3- or 4-wire system, the white wire
of a 2-wire circuit, and the white wire from a 4-wire three-phase 120/240V delta-connected system are not neutral conductors-they're
grounded conductors.
Anyway, I believe that the white IS called a neutral in the UK, but not here in the US (not by the NEC anyways).
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Dennis wrote:

Even in side of industrial panels for 120 volt control wire the neutral is white or though, it really does not have to be white in side of panels but it sure make's life much easier. Gray and yellow isn't used much any more..
The neutral is always equal in load capacity and length of the high side. It's tied to ground only in the service panel where the earth electrode is bonded near by. THe neutral shall never make an earth connection else where.
All runs of H/N to each outlet needs to be of equal length. This is very important especially when it comes to CFCI and arc breakers.
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Jamie wrote:

Why do they need to be of equal length? In some cases the hot runs to a switch and then back to the outlet making it quite a bit longer. In a completed circuit I can't see how it could matter... ?
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Er, I don't think they "have to be", other than as a logical consequence of all of the conductors for a given circuit have to be within the same sheathing (or raceway). Part of this is ensuring you don't get confused as to which neutral goes with which hot.
Most of the time that is...
A light fixture with a switch leg has a hot path considerably longer than the neutral path - twice as long as the switch leg.
This is in contrast to knob and tube where the individual conductors were run independently of each other. They often got confused as to which neutral went with which hot.
I don't believe that different H/N lengths make much difference to GFCI or AFCI, except in extreme and unusual situations. Eg: if you wrapped the neutral many times around an operating fluorescent ballast I could see it tripping a GFCI. _Maybe_.
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Chris Lewis wrote:

That is why many people have problems with GFCI outlets false tripping.
CFCI's work on load and phase balancing with respect to the race ways.
A while ago we had our electricians replace all the commonly used outlets on industrial machines with GFCI's only to fine that many stations were wedging the reset buttons, having the off shift electricians put noncompliance outlets back in for some area's
They had me go out and examine a few cases to see what was up. over the years, outlets were added, separate runs of L1 was feed from the panel for each to have it's own fuse, sharing the L2 line in various places which throws the balance way off of course... Of course, most of the time a little indifference isn't going to matter I had them install a new 120 outlet service system on the outside of these machines totally isolated from the inner panels of the machines with each outlet having it's own L1/L2 and (G) all the way to the distribution panel.
It was a lot of work for them how ever, in the end, they love it now because they can now use the outlets for their tools while working on the machines when the machine is locked out at the buss and panels wide open.
And of course, lighting has not been allowed to use the same outlet circuit for some time now so that's not an issue any more.
And on a side note, something I saw one day at our facility... Make sure the emergency lightly intended for a room is connected to the lighting circuit of that room and not some main circuit breaker for emergency lighting for lets say a building etc.
Inspectors love catching that one along with insufficient length of wire hanging out of switch and outlet boxes when opened for inspection! :) Also, when requested to open the boxes, the inspector may follow you to watch your procedures of how you disconnected the service before doing so. They love to spot unsafe work practices.. :)
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Remember that by definition, a simple two pole device _cannot_ see "phase differences". There's nothing to compare the phase _to_. All it can see are instantaneous voltage between the two leads plus current in the individual leads. You need three conductors (the ground doesn't count here because a GFCI doesn't care about the ground) to see "phase".
Yours was an industrial situation (likely very noisy EMI), and not knowing exactly how these things were wired and what they fed, it's difficult to tell what was going on. Eg: common ground points on what was being fed with the equipment and a tiny bit of leakage on the other leg. Completely isolating both current-carrying leads of the GFCI (as you ultimately did) from the tool would eliminate much of that, without having anything to do with individual conductor length.
It could have just been severe EMI on the line side of the GFCI overwhelming the device or an imbalanced inductive effect.
I really don't think you'd see anything like this in a residential situation.
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In formal documents such as the NEC, it's referred to as the "grounded" or "identified" conductor. However, everybody (including electricians) call it a neutral most of the time.
Check out:
Subject: "grounding" versus "grounded" versus "neutral".
In the electrical wiring FAQ, section 1.
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Tossing my 2 cents worth in here, in a common switched curcit, the hot and neutral will be of the same length maybe the difference of the switch itself, here is how, the romex comes from the breaker at the main panel , goes to a switch box on the wall, then another length of romex goes to the outlet or fixture and is attached to the leads of the fixture or outlet, back at the switch box, the grounds are wire nutted togetther and a pig-tail goes to the ground screw on the switch, the whites are wire nutted together and the blacks go to the switch screws to make the circuit, so for the most part, the conductors are the same length.

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Switches can be wired in two ways:
1) Power goes to switch first, then switched hot and neutral goes to light fixture. This is what you've described above (in a lot more words ;-).
2) Power feed goes to the light first. The neutral is attached to the fixture. Then, the hot feed goes to the switch, and a switched hot comes back to the fixture. These are called "switch loops", and what I was referring to earlier.
I prefer to do 1, but 2 is perfectly legal, and I've seen some books recommending it. It can be somewhat advantageous in certain circumstances.
In (1) the hot and neutral are the same length. More-or-less.
In (2) the hot is longer than the neutral - by twice the length of the cable going from the fixture to the switch.
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I got wordy for the ones that have never worked with wire, switch, outlet, and fixtures

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I know, it's not really a neutral, but most electricians call it one anyways. (It's why I referenced Mike Holt and the IEEE definition). By definition, a neutral only carries unbalanced loads, hence the white wire in a 120 v circuit (which carries full loads) is defined as an identified conductor, not neutral. You say potato, I say pototo ......
It will catch you on a test though.
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JJBDCB had written this in response to http://www.thestuccocompany.com/construction/Re-switch-grounded-outlet-combo-question-11813-.htm : Dennis i dont where u get your info but NEC is a private company white is neutral on 110 in the USA , i take it your not a elecrtian. whit is not just considered just identified conductor !!!!
World Region, country or other entity(ies) Live Neutral Protective earth/ground EU, Australia & South Africa (IEC 60446) brown blue green & yellow Australia & New Zealand (AS/NZS 3000:2007 3.8.1) brown light blue green/yellow United States and Canada black (brass) white (silver) green (green) Standard wire colours for fixed cable (In or behind the wall wiring cables) Region Live Neutral Protective earth/ground EU (IEC 60446) including UK from 31 March 2004 brown blue green & yellow Australia and South Africa red black green & yellow (core is usually bare and should be sleeved at terminations. In Australia the earth core has been separately insulated with green or green/yellow plastic since about 1980. United States and Canada black, red, blue(brass) white (silver) green (green) or bare copper wire Note: the colours in this table represent the most common and preferred standard colours for single phase wiring however others may be in use, especially in older installations.
Since 1897 the U.S. National Fire Protection Association, a private nonprofit association formed by insurance companies, has published the National Electrical Code (NEC). States, counties or cities often include the NEC in their local building codes by reference along with local differences. The NEC is modified every three years JJB ------------------------------------- Dennis wrote:

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