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#1
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Weird electrical problem
I wired my finished basement myself. In general everything was fine, I had
it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: - dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W and 50 W - dedicated 20 A circuit for basement rooms receptacles - dedicated 20 A circuit for sump pump - dedicated 20 A circuit for washer / gas dryer - dedicated 20 A circuit sewer ejector pump - dedicated 20 A circuit for basement bath - dedicated 20 A circuit for garage receptacles - 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220 V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. Can anyone give me a clue what cane be a source of this weird residual voltage in disconnected circuit? |
#3
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You may be using a digital meter that is so sensitive that it is picking
up induced current. Do you have an old analog meter you could try. I suspect it will read 0 -- Joseph Meehan 26 + 6 = 1 It's Irish Math "Alexander Galkin" wrote in message ... I wired my finished basement myself. In general everything was fine, I had it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: - dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W and 50 W - dedicated 20 A circuit for basement rooms receptacles - dedicated 20 A circuit for sump pump - dedicated 20 A circuit for washer / gas dryer - dedicated 20 A circuit sewer ejector pump - dedicated 20 A circuit for basement bath - dedicated 20 A circuit for garage receptacles - 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220 V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. Can anyone give me a clue what cane be a source of this weird residual voltage in disconnected circuit? |
#4
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Alexander Galkin wrote:
I wired my finished basement myself. SNIP When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. If you were reading this voltage at the recept with nothing plugged in on that circuit, then the 8V is perfectly normal reading and is due to stray coupling between conductors. Try the reading again with a lamp or other load plugged in. Jim |
#5
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"Alexander Galkin" wrote in message ... I wired my finished basement myself. In general everything was fine, I had it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: The false indication of voltage caused by a high impedance voltmeter is pretty well known. If that is really the problem, it worries me that the inspector didn't pick up on it. Charlie |
#6
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Alexander Galkin wrote:
I wired my finished basement myself. In general everything was fine, I had it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: - dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W and 50 W - dedicated 20 A circuit for basement rooms receptacles - dedicated 20 A circuit for sump pump - dedicated 20 A circuit for washer / gas dryer - dedicated 20 A circuit sewer ejector pump - dedicated 20 A circuit for basement bath - dedicated 20 A circuit for garage receptacles - 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220 V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. Can anyone give me a clue what cane be a source of this weird residual voltage in disconnected circuit? Are a bunch of your wires running for long lengths in parallel through the same holes in the studs? It is a long shot, but it might be inductive coupling. Were the circuits that had the breakers still on loaded? That is, were lights or other things on such that the circuits had current flowing in them? Typically, if Romex-style cable is used the return current in the white wire should cancel the field from the black wire and thus there shouldn't be any significant net field to affect adjacent wires, however, sometimes strange things can happen. Matt |
#7
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Speedy Jim wrote:
Alexander Galkin wrote: I wired my finished basement myself. SNIP When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. If you were reading this voltage at the recept with nothing plugged in on that circuit, then the 8V is perfectly normal reading and is due to stray coupling between conductors. 8V seems high. I rarely see more than a few hundred mV from inductive coupling alone. To the OP: Did you test every outlet with a tester to verify that all neutrals are connected? I wonder if you have a floating neutral somewhere. Matt |
#8
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Matt Whiting wrote:
Speedy Jim wrote: Alexander Galkin wrote: I wired my finished basement myself. SNIP When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. If you were reading this voltage at the recept with nothing plugged in on that circuit, then the 8V is perfectly normal reading and is due to stray coupling between conductors. 8V seems high. I rarely see more than a few hundred mV from inductive coupling alone. Really? I've often seen over 50 VAC, and still with a load as small as a 7 watt night light, it went down to zero VAC. -- Tony |
#9
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Tony Miklos wrote:
Alexander Galkin wrote: Actually, the problem was accidentally discovered by the inspector that had usual bulb light tester that does not have any scale but just light bulb. What kind of "usual bulb light tester" are you talking about? Are you talking about a little thing with three LED's or neon lights something like this: http://www.inspectortools.com/gfciouttesbu.html If so, it's a worthless piece of crap way to test outlets. I can't believe inspectors are allowed to use them. If the inspector didn't use something like that, what kind of bulb and what wattage is the bulb in the tester he did use? Did you plug in a regular lamp (turned on of course) and at the same time test to see if there was any voltage on the circuit with your multi-meter when the circuit was turned off? I don't see how plugging in a lamp that is switched off should make a difference. The outlet itself is an open circuit. A lamp switched off should also be an open circuit. Please explain how the lamp should affect the open circuit voltage? I'm an EE so don't be afraid to get technical. Matt |
#10
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Tony Miklos wrote:
Matt Whiting wrote: Speedy Jim wrote: Alexander Galkin wrote: I wired my finished basement myself. SNIP When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. If you were reading this voltage at the recept with nothing plugged in on that circuit, then the 8V is perfectly normal reading and is due to stray coupling between conductors. 8V seems high. I rarely see more than a few hundred mV from inductive coupling alone. Really? I've often seen over 50 VAC, and still with a load as small as a 7 watt night light, it went down to zero VAC. Something doesn't jive here. The voltage shouldn't go to zero unless you short circuit the wires. Any light has resistance and any resistance that has current flowing through it will have a voltage across it. The only way the voltage can be zero with current flowing is if the resistance is also zero (a dead short - with a very short piece of wire!). How are you measuring the voltage? Across what terminals? Matt |
#11
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Matt Whiting wrote:
Tony Miklos wrote: Matt Whiting wrote: Speedy Jim wrote: Alexander Galkin wrote: I wired my finished basement myself. SNIP When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. If you were reading this voltage at the recept with nothing plugged in on that circuit, then the 8V is perfectly normal reading and is due to stray coupling between conductors. 8V seems high. I rarely see more than a few hundred mV from inductive coupling alone. Really? I've often seen over 50 VAC, and still with a load as small as a 7 watt night light, it went down to zero VAC. Something doesn't jive here. The voltage shouldn't go to zero unless you short circuit the wires. Any light has resistance and any resistance that has current flowing through it will have a voltage across it. The only way the voltage can be zero with current flowing is if the resistance is also zero (a dead short - with a very short piece of wire!). Are we mixed up again? I thought we were talking about inductive coupling, not a transformer. To keep it in layman's terms, "the voltage ain't got no balls" or *amperage* to back it up. So the slightest load across the outlet will bring it to zero VAC, (close enough for this forum anyway). I've even simply touched across the two meter leads by accident, with no other load on the circuit, and the voltage went from close to 50VAC to below 1 volt. Remember, this is with the circuit off of course, and inductive coupling, not a short or an open neutral, and me as the only load, even with sweaty hands, still probably over 10K ohms. How are you measuring the voltage? Across what terminals? In the outlet, from hot to neutral, with the night light in the other socket of the same outlet. -- Tony |
#12
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Tony Miklos wrote:
Matt Whiting wrote: Tony Miklos wrote: Alexander Galkin wrote: Actually, the problem was accidentally discovered by the inspector that had usual bulb light tester that does not have any scale but just light bulb. What kind of "usual bulb light tester" are you talking about? Are you talking about a little thing with three LED's or neon lights something like this: http://www.inspectortools.com/gfciouttesbu.html If so, it's a worthless piece of crap way to test outlets. I can't believe inspectors are allowed to use them. If the inspector didn't use something like that, what kind of bulb and what wattage is the bulb in the tester he did use? Did you plug in a regular lamp (turned on of course) and at the same time test to see if there was any voltage on the circuit with your multi-meter when the circuit was turned off? I don't see how plugging in a lamp that is switched off should make a difference. The outlet itself is an open circuit. A lamp switched off should also be an open circuit. Please explain how the lamp should affect the open circuit voltage? I'm an EE so don't be afraid to get technical. This time you misread my post. I wrote that the lamp would be turned ON. To quote myself "(turned on of course)" I don't think we need to get technical! Oh crap, now I think I see what you meant. My last line "when the circuit was turned off?" What I had meant, was that the breaker to that circuit of outlets was turned off, but the lamp circuit on. -- Tony |
#13
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Alexander Galkin wrote:
I wired my finished basement myself. In general everything was fine, I had it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: - dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W and 50 W - dedicated 20 A circuit for basement rooms receptacles - dedicated 20 A circuit for sump pump - dedicated 20 A circuit for washer / gas dryer - dedicated 20 A circuit sewer ejector pump - dedicated 20 A circuit for basement bath - dedicated 20 A circuit for garage receptacles - 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220 V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. Can anyone give me a clue what cane be a source of this weird residual voltage in disconnected circuit? Hi, Tried using both DVM and analog meter? Tony |
#14
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Matt Whiting wrote:
I don't see how plugging in a lamp that is switched off should make a difference. The outlet itself is an open circuit. A lamp switched off should also be an open circuit. Please explain how the lamp should affect the open circuit voltage? I'm an EE so don't be afraid to get technical. Betcha the lamp was on and the circuit off. Osmotic voltage (hope you don't mind technical jargon) does something I call "drains." |
#15
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JerryMouse wrote:
Matt Whiting wrote: I don't see how plugging in a lamp that is switched off should make a difference. The outlet itself is an open circuit. A lamp switched off should also be an open circuit. Please explain how the lamp should affect the open circuit voltage? I'm an EE so don't be afraid to get technical. Betcha the lamp was on and the circuit off. Osmotic voltage (hope you don't mind technical jargon) does something I call "drains." Ha, ha, ha... Good one. Matt |
#16
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"Alexander Galkin" wrote in message ... I wired my finished basement myself. In general everything was fine, I had it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: - dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W and 50 W - dedicated 20 A circuit for basement rooms receptacles - dedicated 20 A circuit for sump pump - dedicated 20 A circuit for washer / gas dryer - dedicated 20 A circuit sewer ejector pump - dedicated 20 A circuit for basement bath - dedicated 20 A circuit for garage receptacles - 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220 V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. Can anyone give me a clue what cane be a source of this weird residual voltage in disconnected circuit? voltage is being induced in the disconnected circuit due to its close proximity with live current carrying wires.. the electro magnetic effect created by an conductor. I am currently revamping a 20 year old control system, no big deal, a few pumps, a boiler and a cooling tower... very nice control job these guys put in... 24vdc, the wires are all bundled nicely.. and the job as worked more or less fine for 20 years with a few bugs no one has figured out. in checking out I noticed all kinds of 2 to 9 volt reads in open circuits. Fortunately there were no electronics or logic controllers in this old system so the stray voltages were not sending bogus signals to the electronics... but at 9vdc, and sometimes AC.. and relays operating at 24vdc... I think they got a little sticky at times and is the source of the unfathomable bugs. However moi here is adding a PLC to the mix (dinky solid state computer that does simple logic functions, 256 various combinations)... and If I am not careful the wiring I install will be next to higher voltage conductors that will induce current in my PLC feed wiring.... and the PLC will go nutz... and produce all sorts of bogus output. a bad thang. Fortunately I am putting this low voltage wiring in a separate cabinet and not bundling the wire as the other stuff is bundled so I wont get stray signals. I almost decided to run some 110 vac transformer power wire in the same conduit as the 24 vac control and alarm wiring some of which would go directly to dialers.. no relay in between. that could have been a mess because both the dialers and the PLC are AC voltage.. *any& AC voltage... so say 15vac or 120 vac signal is acceptable as an input to the plc. That would have been messy. The instructions with these particular devices even say you can use DC inputs over a wide range to trigger the PLC switching actions even though they are rated for AC only and sell a strictly DC unit if you want one. So what does that tell a person? That all those trace stray voltages will create havoc in yer electronic gismo's. Sigh. Getting back to your case. Dont worry about it...while there is voltage in the disconnected circuit, its induced and not capable of pushing much amperage, so its harmless in a home wiring sort of scenario/... just a faint distortion to a circuit under load. Phil Scott |
#17
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Phil Scott posted for all of us....
I almost decided to run some 110 vac transformer power wire in the same conduit as the 24 vac control and alarm wiring some Which would be a code violation. -- Tekkie |
#18
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JerryMouse wrote:
Matt Whiting wrote: I don't see how plugging in a lamp that is switched off should make a difference. The outlet itself is an open circuit. A lamp switched off should also be an open circuit. Please explain how the lamp should affect the open circuit voltage? I'm an EE so don't be afraid to get technical. Betcha the lamp was on and the circuit off. Yes, I guess I'll have to learn English! ;-) -- Tony |
#19
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Following advise I plug-in the load (TV) into one of receptacles. Residual
voltage dropped to zero immediately in switched off circuit even when measured by digital multimeter. To verify this I unplugged the TV and voltage jumped to previous ~8-9V. Now I am convinced it is inductive voltage induced by other hot circuit wires running close to the disconnected one. I am calling the electrical inspector to re-inspection. "Alexander Galkin" wrote in message ... I wired my finished basement myself. In general everything was fine, I had it inspected before insulating walls and ceiling and putting drywall. I have been using power in basement for over the year and nothing was wrong. However, on final inspection the electrical inspector and I found a very weird problem that I need now to correct. I have the following wiring diagram in basement: - dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W and 50 W - dedicated 20 A circuit for basement rooms receptacles - dedicated 20 A circuit for sump pump - dedicated 20 A circuit for washer / gas dryer - dedicated 20 A circuit sewer ejector pump - dedicated 20 A circuit for basement bath - dedicated 20 A circuit for garage receptacles - 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220 V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit When I switched off basement room receptacles circuit breaker while all others except sub-panel which does not seem to affect the problem were on we found there is 8 V power in that circuit. Switching off some of other circuits reducing this voltage to about 2 V and only switching off all new circuits brings disconnected voltage to zero as it should be. Can anyone give me a clue what cane be a source of this weird residual voltage in disconnected circuit? |
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