608 reputation
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bio website ericlippert.com
location Seattle, WA
age 41
visits member for 3 years
seen 2 days ago

Eric Lippert develops C# analyzers at Coverity. During his sixteen years at Microsoft he was a developer of the Visual Basic, VBScript, JScript and C# compilers and a member of the C# language design committee; he is now a C# MVP. He is on Twitter at "@ericlippert" and writes a blog about programming language design and other fabulous adventures in coding at http://ericlippert.com.


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comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: That I don't know. I've never seen that behaviour in a multimeter.
Oct
22
comment How do I fix a broken brass drawer pull?
Then I'd go for brazing on new metal as the answer suggests.
Oct
22
comment Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
@speedypetey, well I am glad to see that you posted an answer independently of my encouragement. You're obviously passionate on this subject, which is great. Incidentally though, I did once encounter a shared neutral circuit with a single phase, a mixture of romex and knob and tube, running through blown in insulation that had rats living in it chewing the shared neutral and one hot. It wasn't on fire, yet. How many more things would have to go wrong to cause a fire, I wonder?
Oct
22
comment Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
@speedypetey I have no doubt that a professional electrician would recognize a problem, know what to look for, and do it right the first time. My concern is not for the pros, its for the amateurs who don't have any experience. I'm no pro, but I've seen enough dangerous homeowner wiring to be very conservative when advising novices. Again, why not write an answer you like better and we can all learn from?
Oct
22
comment Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
@speedypetey you will find several questions on this site from people who have miswired gfcis on shared neutral circuits. I had one in my house which I only discovered by installing a gfci wrong, not knowing there was a miswired Edison circuit. If you don't like this answer, why not write one you like better?
Oct
22
comment Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
@ecnerwhal i am well aware of how currents add. you are correct right up to the point where someone figures they can rewire the panel to run both branches on the same phase. Which the previous owner of my house did. Do not underestimate how foolish people will be with electricity. A shared neutral circuit is a trap for the unwary.
Oct
22
comment How do I stop a dimmer switch from humming?
What brand is the dimmer you bought?
Oct
22
revised Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
added 30 characters in body
Oct
22
answered Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
Oct
22
suggested suggested edit on Can I branch off of a 2 pole 30 amp 10-3 wire found abandoned in a junction box?
Oct
22
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: Also, as I always counsel people who are getting into homeowner wiring: if you do not have a solid grasp on what the relationships are between volts, amps and watts, if you can't off the top of your head immediately say that a 60W bulb will draw 0.5A on a 120V circuit, then learn that before you go on. You wouldn't want a contractor to work on your house who was not clear on the difference between pounds, inches and minutes, so don't be a guy working on electrics who confuses current, potential and power.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: More generally, you want the neutrals to have the property that any neutral wire on a given circuit is an uninterrupted path back to the neutral bus on the panel. Similarly for safety grounds; you want there to be one grounding system in the house that all the safety grounds tie into. When I bought my house there were two, and therefore it would be rare but possible to have a voltage difference between them.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: Imagine a light fixture hooked up directly to the breaker. The light is on all the time. Now you decide to introduce a switch to control the light. You can put the switch on the hot wire or the neutral wire; either will cause the light to go off when the circuit becomes open. But if you switch the neutral then the hot is unswitched and is always providing voltage to the light fixture. That is far more dangerous than the alternative, so code is to always interrupt the hot when you add a switch.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: An "open" wire is a wire that is not at present connected to anything, so an open ground is what looks like a ground wire, but in fact is not connected to a copper rod driven into the earth anywhere. An open ground is dangerous because it looks like a safety system but in fact is no such thing. An open wire is called that because normally you make a wire open by opening a switch. Internally the switch has a mechanism that physically moves two wire ends together or apart; if there is a gap, no current flows. If the gap is closed, current flows.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: Not realizing that the ground was open, I tried testing a white wire against the ground, got no voltage, and concluded the white was neutral. It was hot. It was on. I could have shocked myself or others. I should have tested against a known ground rather than assuming incorrectly that the ground was the only correctly wired thing in the box. I have a healthy respect for just how terrible homeowner wiring can be; again, proceed with caution as you learn how to do this.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: Case in point, I recently rewired a friend's bathroom light where the previous owner had a box in which black, white and red wires were all used for hot and neutral; at one point there were red, black and white wires taped together. Everything was held together with tape, the grounds were open, and the switch interrupted the neutral. If there was a way to do it wrong, they did it wrong.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: That's right. The safety ground of course is never interrupted in a correctly wired box, but again, you don't know whether the wiring you are investigating is correct. That's the point of the investigation. So proceed carefully deducing new facts starting from known facts, like "this is a good ground, this is a good hot".
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: There are lots of videos on the internet on how to use a voltmeter; if you're going to be diagnosing electric circuits then knowing how to use this tool correctly is going to be important, so I would start there.
Oct
21
comment Is there a way to change this circuit so that the receptacles are not controlled by switches?
@MarkTraina: A voltmeter will only tell you that there is a voltage when it is part of a circuit. If you touch a voltmeter probe to a hot wire but do not touch the other probe to anything, that tells you nothing because there is no circuit. If you touch it to a piece of metal that is not grounded, that's not different; the probe is already a piece of metal that is not grounded. To test whether something is hot, you need a known ground. And conversely, to test whether something is grounded, you need a known hot.
Oct
21
comment How do I wire a ceiling fan?
Nothing says "dangerous amateur" louder than finding wires wrapped in electrical tape. Use wire nuts.