Home AC Outlet - Voltage On 'Off'

You are probably just picking up (electromagnetically) induced voltage. If you are checking the voltage with a digital multi-meter, they have a very high impedance, and will show that voltage.

If you can afford it, or you can borrow one, try using something like this instead.

Thank you for your reply. I have a Fluke T5-600 Will it pick up the induced voltage?

Hard to tell. None of the literature I saw, said that it was low impedance.

Hopefully someone else here is familiar with that model, and will answer.

Is the wall switch the type that is illuminated? If so, you could be seeing a voltage bled. With the wall switch off, what's the voltage between "hot" to ground and neutral to ground? You might also check the neutral to ground with the switch in the "on" position and nothing plugged in the outlets.

Can't find it on the Fluke site, but several suppliers quote the input impedance for voltage measurement as ">1MΩ". This is definitely high enough to give a reading of 35V from a couple of ungrounded wires running near others carrying mains AC.

This is probably an induced voltage. Induced by the one wire laying next to the other. Could also indicate poor grounding. The earth/ground wire should also be laying next to the A and N wire and conduct induced voltage to ground. I had 240V on an earth/ground wire that was all induced voltage. Found that the installer hadn't connected the wire to the terminal block. Gave a huge, loud spark when put near the tin roof. ( about 5mm ) Jim

You didn't mention if the tested voltage was on the switched or unswitched sides of the duplex.

Remember in a system, you have a main panel with circuit breakers. In a simple system, you will have one main circuit breaker ( could be 30-50 amps) and several branch circuit breakers ( 15-20 amps ).

If any or all of the branch circuit breakers are off and the main circuit breaker is on and you detect voltage, this could mean that one or more of the branch circuit breakers are leaking voltage.

If you turn off all of the branch circuit breakers and you turn off the main circuit breaker and you detect voltage, this could mean that the main breaker is leaking voltage.

A voltage leak can be observed by placing your voltmeter leads onto neutral ( white wire ) and ground/earth ( usually the ground is a bare copper lead ) or black to ground, or red to ground - in a 3 wire branch circuit.

Houses are usually wired with Romex. For example, Romex can be 14/2 , this means that there is one black wire and one white wire, then you can have 14/3, this means that one wire is black, one wire is red and one wire is white. Some Romex cables have an uninsulated ground and some have an insulated ground.

In some cases, detected voltages can be between 25-35 volts.

As a matter of safety, when I work on a circuit, I always shut off the main and before i start, I always check for residual or leaking voltage beforehand.

If you believe you have an issue with your system, contact an electrician for assistance.

You may find it useful to review parts of a thread back in February 2013 regarding "LED light bulbs", especially my posts #61 and #71.

http://cr4.globalspec.com/thread/82870#comment1150899

The above link may well take you to some other comment within that thread, but post #61 refers to a set of experiments I did to prove why you are measuring that voltage.

It is capacitive coupling, the insulation is your dielectric, the conductors are your plates. One live conductor (the top outlet conductors) runs alongside the switched conductor for a good distance, providing enough capacitance to build up a measurable voltage on the floating plate.

I've measured voltages as high as 85Vac (phantom) on a system with 120Vac supply max, in a mess of cables buried under the floor in an industrial facility. I used to think the maximum was 60V, half of the supply voltage coupled to ground. We see anywhere from 5 or 6, to the highest I saw at 85V.

The current flow is very low, you see the charging current (as mentioned before), is very low, and any kind of load, including your finger (nightlight SolarEage/Rixter)(Wiggy type meter or ET200(Kilowatt0), will drop the voltage to near zero.

Check voltage between Neutral and earth; should be less than 0.5V AC; if not wiring must be thoroughly checked.

The voltage on the neutral is a function of the neutral current and the earth loop impedance. So you can't say that.

That's the problem with unspoken assumptions, such as neutral being earthed with less than V/I resistance....

Plug in a load while it is switched off and the voltage should disappear. If it does then the problem is simply a failure to recognise that a high input impedance voltmeter is picking up an induced voltage as a result of being close to an AC socket and its wiring. If it doesn't, then you have a faulty socket, which is £6 and 1/2 hour's work to fix.

I didn't know that the, " ( £ ) " was the type of currency used in France.

You probably do not have a problem. Use a "wiggy" to measure the voltage. You will find that the voltage is nonexistant.

You didn't explain completely where you were detecting power. Presumably, between hot and neutral.

But: It is possible for a "backfed neutral" to be carrying power. This happens when two or more circuits share a neutral. For example, one light bulb can be turned on, the current is returning to the panel through the neutral. Another socket sharing that neutral can show voltage to ground on that neutral.

You didn't say how old this building / building wiring is. In the north eastern states , if someone hasn't gotten scared enough of old wiring and replaced it, you can still find houses where they switched the neutral, not the live leg. With a multi-meter, you would notice that live side even with out a true ground, as noted in previous replies from others. (I know from experience at my Grandfather's house - sure jolts you when you think you have a light socket turned off)

You have a digital switch on the wall that uses a triac. Leakage on triacs is the norm rather than the exception. No big deal. If you need to get zero, you need a digital switch using a relay rather than a triac.

I certainly do hope this is "ghost" voltage (EM pickup from nearby wires), and a high impedance measurement, but what if there is a lot of current on neutral somewhere nearby. That could mean there is actual voltage present on neutral that could be a hazard.

Check each against ground, please. Also do the plugged in lamp test. Get back with us.

After further review, I see that my answer is several days and a dollar short of being relevant.