The house I'm in how has 2. MAIN on a panel inside, and one for the central A/C.
Strangely, a neighboring house which was built at the same time and also has a Square D panel, has no MAIN (and no double-pole breakers either).
You're referring to the situation when the neutrals become somehow disconnected from the neutral busbar, but remain connected to each other. One specific instance of that problem happens in a shared neutral circuit, and is why shared neutral circuits are "bad." However, you're referring to a situation with a fault.
The GP is warning that if the OP's house has shared neutral circuits, the neutral is live, even without any fault, when only the breaker for one side if turned off.
"Allowed up to six main disconnects"?
Yes. I did find that other wording strange. The first time I saw it, I thought it was saying that some services REQUIRED that many (like they'd be illegal with only 5, even if that shuts off everything).
If you have a very small service that's only for lighting a
10-square-foot outhouse, that may just need one breaker BUT YOU MUST STILL HAVE SIX MAIN DISCONNECTS :-)
I apparently have Spambait plonked, as I don't see his posts, only Nexus replies. Perhaps his responses indicate why I have him blocked.
Residential romex circuits tend to have separate circuit neutrals only because of the nature of the wire. Commercial will nail you to the wall. Very few circuits have their own neutral. In my original reply to the OP, I would rather preach chapter and verse. Always check for a back fed neutral or shared neutral.
The number required is equal to the maximum load in amps, divided by
30 and limited to six. For loads not over 15A, the required number is
Yes. The important thing about teeth is often that you have them with you.
12V it getting strong for that (using the tongue as a voltage tester). It works OK with 9V batteries. And that's DC. IIRC I've never tasted AC, but I hear it's even stronger.
I have described the feeling of such voltages as "a thousand hyperactive ants just under the skin".
I've had such a thing happen (unintentionally) before. There was a problem (since fixed) with the cable here. If you disconnect the cable, you get 30VDC between the shields. This disconnection was at moth level and the loose end hit me (I really don't remember how BOTH ends did at the same time).
It might be useful if the meter had a button you could press to add a load and see if the voltage changes.
Here, I've measured 50VDC on a phone line with no load. I don't have any current measurements for it, but I do notice the impedance to be high (any load will lower the voltage you see). The ring signal is
75VAC superimposed on the DC so it varies from -25V to 125V. I think the impedance of the ringing signal is much lower, allowing significant current.
Maybe it's the breaker you THOUGHT was off, or there's another circuit in there and you don't know it.
And don't forget that 50V line voltage is present too. Since that is DC and the ring is AC, the voltage on the line is varying from the difference to the sum of those.
I know what was referred to and some person reading that would assume that ALL panels were dead inside when the breakers/fuses marked main were off/pulled, which is just not so in thousands of both old and new homes. killing the Main and then sticking a had in the box is asking for death and people that know little or nothing about electrical distribution panels need to be aware that there are differences.
Tom J
20+ years ago I needed a new svc. panel. I looked at such split buss panels and recoiled. Installed the simplest imaginable 200a panel with "The One True Main" breaker and never regretted it.
As I recall, such panels weren't much more expensive than split buss. A professional electrician would do much better than I with split buss, but it's hard for me to imagine a complex job being easier with split buss, regardless of training/experience.
Just curious. Why were (residential) split buss panels so extensively used?
Cheers, Puddin'
"Life is nothing but a competition to be the criminal rather than the victim." - Bertrand Russell
Haven't got a clue. I hate the damn things, not to mention how potentially dangerous they are. With a single main disconnect, say 200 amp, when your load reaches that point, it trips. With a split buss, you "could" have six
100 amp main disconnects on the same 200 amp service, depending upon the actual load in the building, presuming it's less than 200 amp. Thirty years goes by, countless DIY's , handy men, etc, and who knows what's actually being drawn through the service conductors
As in, the vast majority of residential circuits in the United States.
Yes, of course -- but the question asked was whether it was possible to get shocked with the breaker turned off. Turning off the *wrong* breaker is not the condition specified in the original question.
Sorry -- I'll try to make the explanations a little simpler for you.
I haven't seen this mentioned yet, and wait for others to confirm before you attempt repairs. If you touched your voltmeter to the wires on the dimmer, I wouldn't expect to see any voltage at all. The two wires there are the load side of the circuit (black wire) and you won't show voltage there. You need a neutral or ground to complete the circuit with your multimeter.
In some houses, touching the metal box provides a ground. Something I do is to plug in an extension cord and use the ground portion of the plug (having tested it for polarity and ground) to complete the circuit, along with the switch.
If you weren't touching both wires to the switch, but the power pigtail and the neutral pigtail, then nevermind.
That depends on whether the dimmer is on or off -- if it's off, I'd certainly expect to see voltage between the two terminals on the dimmer, wouldn't you?
The circuit is completed through the light bulb(s).
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