Neutral-to-ground voltage shocked me today; cause?

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maybe this will help explain things better

shocksurge.JPG
 
crossman said:
For a capacitor to provide voltage and current for AC circuits, there would have to be an inverter to convert the DC cap voltage to AC sine wave voltage. I doubt a surge protector would do this. A UPS system, yes. Surge protector = no.

To get shocked from a multi-wire BC neutral, there has to be a load connected to the other circuit. Unplugging the surge protector would have removed the load on the neutral.
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No UPS, but there was a battery on the system. It would've been in the laptop that was plugged into the surge protector.
 
Hmmm...maybe I'll try and re-create the setup of a laptop plugged into a surge protector and see if I measure voltage on the plug. The only thing I can think of is that maybe the laptop battery is reverse discharging through the rectifier, but I don't think that is possible due to the one-way flow properties of the diodes in the power supply.

So you have checked the other existing light box and the outlet box that the surge strip was plugged into and there are no other circuits or wiring in them? You say you measured 100 V on the surge strip plug or where you were shocked?
 
wirenut1980 said:
Hmmm...maybe I'll try and re-create the setup of a laptop plugged into a surge protector and see if I measure voltage on the plug. The only thing I can think of is that maybe the laptop battery is reverse discharging through the rectifier, but I don't think that is possible due to the one-way flow properties of the diodes in the power supply.

So you have checked the other existing light box and the outlet box that the surge strip was plugged into and there are no other circuits or wiring in them? You say you measured 100 V on the surge strip plug or where you were shocked?
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I first measured voltage at the point I received the shock, and then traced it back to this surge protector.
 
It doesn't hurt to measure open circuit voltage, and voltage under load (let's say using a 7-1/2w bulb), to gauge the Thevenin impedance.
If it's voltage through cable capacitive reactance the voltage won't hold up with the bulb across the line.
I carry a 100 ohm 100w rheostat for this type of testing.
 
Long long time ago, it was common to switch the neutrals. This being the case, you'd have a hot wire at the fixture. Did you turn off and lock out breaker or wall switch?
Bob S.
 
bobsherwood said:
Long long time ago, it was common to switch the neutrals. This being the case, you'd have a hot wire at the fixture. Did you turn off and lock out breaker or wall switch?
Bob S.
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guys i appreciate you trying to help me figure out what caused this, but PLEASE read the thread before responding.

This has nothing to do with a MWBC.
This has nothing to do with a hot/neutral reverse.
 
brantmacga said:
I had a situation today that I haven't encountered before:

Job was to install track lighting opposite of existing tracklight. With the circuit off, I found the switchleg in the attic and started to make a tap. When took hold of the cable end going to the existing light, I got shocked. I only had my wiggy in my back pocket and took a quick reading. The cable end going to the switch was dead as it was supposed to be. The cable end going to the light measured just under the 120v line, so lets assume it was somewhere around 100v (it felt weaker than 120v but I could be wrong).

I went back into the room where I was adding the light. I took the bulbs out of the existing track light and had the same voltage reading. Below this light was a receptacle with a computer plugged in through a surge protector (apparently on the switch leg). I uplugged the surge protector and checked voltage at the lampholder again: nothing. The voltage was coming from the surge protector itself. It was called a Panamax Max 4.

Was a capacitor discharging discharging and passing through and MOV or something? I haven't seen this before, so I'm just unsure how it got between the neutral and ground.
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Ungrounded neutral?
 
maybe a neutral is made up in a box along the way that taps into another circuit and backfed to your box.

we cannot see in walls, so there could be a hidden j-box with a neutral cluster that comes from other circuits.

unless you can see the romexes from start to finish, and i did not get that part.

edit: just looked up this product and it does look like it could be full of juice. I was eliminating all possibilities, such as a circuit that was switched on and off at the same time you pulled the plug. Scientific method and all.
 
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