I have an issue in one room where the electrics suddenly no longer work and this issue is confined to only that room. Checking the wires to the electric and light boxes, the white wire is running at 120V, the same as the hot wire. I assume the issue must be a hot wire touching the white wire somewhere in the circuit, but welcome other thoughts and ideas on how to identify where the issue is, or anything else that may be causing the problem.
White wire running hot
- Thread starter daddyharris
- Start date
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P
Paul_C
I assume you're measuring the voltage on the white wire to ground?
The most likely cause of your problem is a bad connection on the grounded conductor (white wire) somewhere. A short to a hot (black) line would trip the breaker or blow the fuse.
When you get a break in the white somewhere, the end which is still securely connected to the neutral bar in the distribution panel will remain at near ground potential, while the end on the other side of the break will rise to 120V due to the electrical path which is present to the black supply line through lamps, appliances, etc. which are still connected. It could be a loose connection for that branch circuit to the neutral busbar in the panel itself.
The most likely cause of your problem is a bad connection on the grounded conductor (white wire) somewhere. A short to a hot (black) line would trip the breaker or blow the fuse.
When you get a break in the white somewhere, the end which is still securely connected to the neutral bar in the distribution panel will remain at near ground potential, while the end on the other side of the break will rise to 120V due to the electrical path which is present to the black supply line through lamps, appliances, etc. which are still connected. It could be a loose connection for that branch circuit to the neutral busbar in the panel itself.
HI
Check the voltage between the white and the black in that room.
See if you get 0v or 240v.
Check the voltage on both to ground.
Mike
Check the voltage between the white and the black in that room.
See if you get 0v or 240v.
Check the voltage on both to ground.
Mike
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Paul_C
Unless the faulty branch circuit is of the multi-wire type, in which case it would have a red wire as well, the only way to end up with 240V between black & white would be a bad neutral connection on the feeder to the distribution panel. If that were the case, the fault would be affecting more than just this one branch circuit.
But I was taking the original poster's comment about finding 120V on the white wire as well as the black to mean that he was measuring between each circuit conductor and ground, in which case 120V on what should be the grounded circuit conductor is indicative of a break or poor connection somewhere in that conductor.
Yes
The US will bring two or three 110v lines in to a big house.
They will run lights on one line to N at 110v.
They will run big AC units and cookers across two 110 lines to get 220v.
Three phase motors are 3 by 110. Its safer from the point of electric shock, but they have untold fires started by the heavy currents and poor protection.
Mike
The US will bring two or three 110v lines in to a big house.
They will run lights on one line to N at 110v.
They will run big AC units and cookers across two 110 lines to get 220v.
Three phase motors are 3 by 110. Its safer from the point of electric shock, but they have untold fires started by the heavy currents and poor protection.
Mike
P
Paul_C
3-wire 120/240V service has been the norm for decades, even for small homes to provide the higher voltage for ranges, dryers, larger A/C and heating units, etc. Three phase services can be found in some cases, but is relatively rare as single-phase 120/240 will be provided for 200A or even more.
Larger apartment blocks often have 3-phase 120/208V services though, with each apartment being fed from two of the three phases.
Three-phase motors are generally 208V, 240V, or 480V, the first for connection to a 120/208V wye system, the second for use with the different types of 240V delta services, and the third for use on 480V delta or 277/480V wye supplies.
I don't know what you mean about poor protection. An NEC-compliant installation will result in perfectly adequate protection. Current is dependent upon the power involved and voltage. While for a given power it will obviously take twice as much current at 120V than at 240V, 120V loads tend to be relatively small, since even in the domestic environment heavier appliances like stoves, dryers etc. are using 240V.
P
Paul_C
It can be a problem at times, although for heating appliances obviously it just reduces the output somewhat. A lot of appliances such as wall-mounted heaters are dual rated for 208 or 240V by the manufacturer. In the case of a dryer it doesn't affect the motor, as that's normally 120V, as are motors for fan-assisted ovens etc. in ranges plus other ancillary equipment such as clocks, timers, etc.
Air-conditioning units which are intended for a simple 2-wire supply without neutral are probably the main problem, so use of single-phase 208V types instead of the more usual (in residential) single-phase 240V types is common.
Not if they're manufactured to that specification
I'll tell you what I mean by poor protection.
I was in the Bahamas, on US 110v wiring.
I saw a flat twin cable smouldering and the burn pont traveling slowly along its length, as it was drawing over current. It was starting to ignite the wood floor.
The bellend that installed it, had run the twin cable across the floor and a SCUBA tank had been dropped on it causing a high res short.
The 25amp breaker held in and a fire was about to break out.
Look at electrical initiated fire stats in the US.
Mike
I was in the Bahamas, on US 110v wiring.
I saw a flat twin cable smouldering and the burn pont traveling slowly along its length, as it was drawing over current. It was starting to ignite the wood floor.
The bellend that installed it, had run the twin cable across the floor and a SCUBA tank had been dropped on it causing a high res short.
The 25amp breaker held in and a fire was about to break out.
Look at electrical initiated fire stats in the US.
Mike
P
Paul_C
Do you mean SPT flexible cord?
And you haven't seen carelessly routed cords which have been damaged in Britain? Or cables installed which aren't large enough for the job and are running hot?
Any particular national system is liable to have things like that happen if (a) somebody installs equipment without really knowing what he's doing, or (b) apparatus and cords or cables are damaged by careless use or handling and nobody bothers to check them or replace them.
I don't know the specifics about what's considered the norm in the Bahamas, but as far as the U.S.A. is concerned the National Electrical Code restricts 120V receptacles for general-purpose use to branch circuits of 20A maximum, which provides adequate protection for appliance cords unless they're under code size.
Hi Paul
I have worked all over the world with British, US, Canadian, African and European wiring systems and technicians.
As an example of protection and regulations.
One US guy worked for the utility company in the US and told me that if a hot line into a house went to ground, they would just switch the Hot line and N over at the incomer, and call it fixed.
Thus leaving a live wire to every appliance when the all N wires become switched and not the L wires.
This breaks every rule in our book. We could not do it in the UK as the protection would trip.
The US has different standards to the UK.
Did you manage to get the US Electrical initiated fire stats yet, we are all interested to see if I am correct.
Mike
I have worked all over the world with British, US, Canadian, African and European wiring systems and technicians.
As an example of protection and regulations.
One US guy worked for the utility company in the US and told me that if a hot line into a house went to ground, they would just switch the Hot line and N over at the incomer, and call it fixed.
Thus leaving a live wire to every appliance when the all N wires become switched and not the L wires.
This breaks every rule in our book. We could not do it in the UK as the protection would trip.
The US has different standards to the UK.
Did you manage to get the US Electrical initiated fire stats yet, we are all interested to see if I am correct.
Mike
P
Paul_C
I think perhaps you missed something there, maybe swapping over two conductors at both ends, if the service lateral is of a suitable type?
Aside from the issues you mentioned, you can't just swap two of the supply lines over (except for swapping the two outers) on a 1-phase 3-wire system because it's supplying both 120 and 240V. And the neutral will have an earth electrode connected to it at the service entrance as well, not to mention the fact that all the pipework etc. will also be bonded to that point.
I haven't been looking. Why don't you post the comparative statistics you're using?
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