Home Wiring

1. I highly recommend letting a pro work on the breaker box. 220 does not just give you a poke - it kills.

2. If you don't take my advice at #1 you should at least have a second person watching you and knows not to touch you in case you electrify yourself.

I wonder if you get the same 2.5 VAC between the ground and the two incoming feeds at the breaker box?

GA

To my mind the OP is searching for a problem that simply does not exist....His phases are slightly unequal in loading, as in 99% of most houses......

You do not get 2,5V between neutral and ground anyplace without reason. We can discuss that. What you forgot to tell us, what current will be produce, when measured. Let's say, that 5 mA collapses it to 0V - it is an intense curiosity = who leaks?!?

If it takes 10Amps, you have a serious problem.

If you take the "normal" case of the pole transformer having a ground rod, and your service entrance having one, a few volts difference can arose naturally.

Your measurement will tell the difference.

Which neutral wire, and where? One possibility could be a loose wire nut on some neutrals that are connected together. This could be a bear to track down.

i think your right. thanks

Go to your breaker panel, do not open it! There should be a single bare conductor coming out of it, do not touch it! Visually follow the wire to a ground clamp that is either attached to a ground rod or the street side of your water meter.

Put one hand in your pocket and use the other hand and an insulated shaft screwdriver to tighten both the ground clamp screws and the screw where the grounding conductor is attached.

If that doesn't solve your problem call a professional, you probably have a poor ground in your panel or the meter pan, worst case scenario is your utility has a poor ground on its equipment and you definitely don't want to go there.

If you don't believe that the voltages floating around can kill you just remember why GFCIs were invented, they trip on less than 30 milliamperes and under 30 milliseconds, your heart will stop long before a regular breaker will open, if at all.

First off how old is your electrical system?

Years ago the ground and the common buss bars in the fuse or breaker box were wired separate. Now the ground and common are the same buss bar so all grounds and commons in the whole system all share a common point at the main panel.

The old split systems often time did not have a solid connection between the grounding and common circuits so it was possible to get odd voltage offsets in the system. The simple fix is to just add a solid jumper between the two in the panel.

If you have 120v between the hot wire and ground it is as it should be. So you concerns about the loss of ground is unfounded. Sounds as if you have lost the neutral. It could very well be that the wire has come loose from terminal in the panel. But first you give test voltage is that at every outlet? You need to know as it could be else where.

If you have never done this before seek help from a professional! Take this from someone that has done the work both residential and industrial. You never know what you may find working behind someone else. Their poor work may jump out and bite you.

Doesn't sound like you know what you are doing as your info is vague. 2nd you didn't discribe what was wrong, other than a reading that sounded like a battery test. Regardless: Hire someone who knows what they are doing!!!! People don't be cheap or stupid there are pro's who need work. And don't tear apart something and then call a pro and expect them to reassemble it for cheap either. It is insulting to say the least. Hope you have some common sense-Good luck That's why wives call us to fix what their former husband fixed!

First are you useing a digital volt meter ? if so you may be getting faulse readings try measuring the voltage accross a load of some sort like a light bulb & see what you get typically the earth & neutral are bonded at the switch board & there should be no potential between earth & neutral.

I personally have found digital multi meters have given readings of several volts on wires I knew were not connected to any thing but were in amongst other wires that were in use. This happens when the internal resistance of the digital multimeter is too high to put a load on the supply. The old analogue meters were not so sensitive & lower internal resistance & did not give the faulse readings. I have found digital meters would still read full line voltage from a blown pole fuse when no load was on it

But if you can still measure voltage across the light bulb or it lights up between earth & neutral I would urge you to get assistance from someone qualified as there is a fault in the earth & neutral circuit in your house & this can cause situations of lethal voltages applied to the metal case of earthed appliances

If everything in the house is unplugged and turned off including the doorbell and furnace, how about turning off the main, and then checking for continuity (ohms) between hot and ground, hot and neutral and even neutral and ground for that matter. I'm even thinking it might be helpful to turn off all the breakers, and then turn them on one by one to help troubleshoot.

Sounds like an open in the neutral or the ground. I assume your wiring problem is a recepticle that doesn't work but you have 120v to the hot wire. Sometimes transformer action between the wires generates 2 or 3 volts but the neutral and the ground usually go to the same terminal bar in the panel and there should be no voltage between them unless you have an open as in a failed wire nut, failed gang connection on a recepticle or broken wire. Some recepticles have a push in wire connection that fail to make contact Never assume any neutrals or ground wires are dead as they can have an open and be powered through a 120v appliance and fry you just as easy as grabbing a hot wire and a white neutral or a bare ground wire with a bad connection can start a fire just as easy as the hot conductor. Call an electrician

You are not alone. 9 out of 10 homes will exhibit similar reading. 2.5 volt can be overlooked, without any danger.

<Sigh> Once again for this forum, a voltage betweeen neutral and ground/earth is simply an expression of the neutral current and the earth loop impedance.

Ignore it. It is of no relevance.

If there is any current flowing the neutral will be a volt or 2 higher than the ground. Current will flow in the neutral under normal operation. Current should flow in the ground only during fault conditions. Are there any actual problems with stuff working in your house? You seem to have uncovered a properly working electrical system.

With single phase appliances, current MUST flow through the neutral in a correctly connected appliance over the appliance cable, to the wall socket, then via the house wiring, at least till it gets back to the switch box (but that is a further discussion on its own!)....

In countries where 3 phases come into the house like here, we also have some 3 phase appliances, big circular saws for example, where NO CURRENT flows through the neutral, simply because the appliance does not even have a neutral connection as none is needed.....that thought foxes a lot of amateurs.....

I think under theoretical proper working conditions there should be no potential difference between neutral and ground.

If there is, the most likely cause is the ground and neutral connection at the breaker box where all the neutral wires are tied to all the ground wires at a terminal strip.

That being said, there will always be some variation in resistance in the system that leads to some leakage. My own bench has a potential difference of about 1.4 VAC.

Bear in mind, when taking those readings the load (DVM) is an extremely high impedance, so 1.4 VAC will probably collapse to near zero with a lower impedance.

The better way to test the circuit is with one of those socket testers you can buy at the hardware store. They light up and let you know if there really is a fault or not.

<...under theoretical proper working conditions there should be no potential difference between neutral and ground....>

Whenever there is a current flowing in the neutral downstream of the neutral-to-earth/ground connection, there will be a voltage between neutral and ground/earth, representing the neutral current multiplied by the impedance of the neutral conductor between the load and the neutral-to-earth/ground connection point.

<...the most likely cause is the ground and neutral connection at the breaker box where all the neutral wires are tied to all the ground wires at a terminal strip...>

The most likely cause is the neutral current flowing correctly and normally in the neutral conductor.

<...there will always be some variation in resistance in the system that leads to some leakage...>

If all cables and appliances are correctly installed and safe, there will be negligible leakage current between phase and earth/ground and between neutral and earth/ground.

• It is not possible for a leakage current to flow in a double-insulated appliance as there is no earth/ground conductor downstream of the wall socket for it to flow in.
• Were there to be a leakage current in an earthed installation, then any individual touching a disconnected earth/ground conductor attached to and upstream of the leakage point would receive an electric shock.

Neither of these two possibilities has any significant bearing on the voltage between neutral and ground/earth.

What has changed on the installation since the last-dated qualified electrician's Test Certificate was produced?

I agree with posts 13 & 14. The voltage has to be the result of induction. Without current flowing the difference in voltage between the neutral and ground cannot be due to a voltage drop in the wire or connections.

I have rewired three homes including moving the service entries. Most of the time I measure 0V between ground & N. But in one home I was measuring a small voltage between the ground wire and neutral as well as between the ground wire and the conduit. I wasted hours attempting to eliminate the voltage. The length of wire between the receptacle and the service entry was the shortest run in the house, less than 20 feet. Nothing I did could eliminate the 2.5v. I tried turning off all of the circuit breakers except for this one circuit. I tightened the conduit connections. I re-terminated the connections in the breaker panel. I even pulled out the wires and inspected them.

Finally, I had to give up. I connected the ground wire to the J-Box as required by the building code and installed the GFCI receptacle. The GFCI tested good and the building inspector signed it off.

(The one thing that I did not try was to slightly twist the hot and neutral together and then pulling them back into the conduit. If I still lived in the house I would spend a few more hours just to see if I could solve the mystery. It has been over ten years and it still bugs me that I did not solve this one.)

I'll concur with Joshi, lightninglou and PWSlack's diagnoses. I'll also add that the distance from the breaker panel (where the neutral is bonded to the ground) and the receptacle will make this voltage higher. For an outlet close to the breaker panel, you may see no voltage; for an outlet that is 75 or 100 feet away from the panel it will be higher. Either way it's not normally a cause for concern.

Another possibility depending on the length of the run is you are just measuring the voltage drop over the length of the neutral conductor Just like if you have several lamps in series & you measure the voltage drop across 1 of the lamps in the circuit it will be a portion of the supply voltage to the circuit.

A 2.5 volt drop on a cable is very small & not a problem & as many others have said I don't think you have any reason to be worried about this

Please connect two LED in parallel, anode-cathode, anode-cathode of each twisted back to back (perhaps, I am not able to express my thoughts clearly across) and connect these across 2.5 V fault line. If the LEDs glow or go bust, only then, you should be concerned. In the contrary case, you can overlook it and have peace of mind.

thanks guys, all g.a.

How much is the circuit loaded when you test it and what is the circuit rated for?

At this point jl has had many good responses from concerned people and I'm wondering if he had no problem but was concerned about the 2.5 volts shown on the neutral to ground. It is more visible with today's digital meters and I have often seen 2 to 3 volts on the hot wires to ground or neutral even after turning off the breakers. A digital will also show a voltage potential between your car or an aircraft and a ground rod. That's why they ground a plane before refueling. May be static charges, induced charges from other nearby conductors or Tesla's aether LOL. With 60 cycle a 1/4 wave antenna is 4,100 ft long if my math is correct. Just something to think about. It would also be interesting to know if jl's 2.4 volts potential shown on his digital meter is 60 cycle or something else and how many conductors turn into antennas when not in use? 60 cycle carrier wave communication was used also by the power companies if my memory is correct between transformers.

If one holds the prods of a DVM tight between two wet hands, we will get a reading, albeit in millivolts. Similarly when we touch the prod of an oscilloscope on AC range, we would behold 3 phase AC waveform. To get 2.5 V between neutral & earth is not abnormal.