Current in Neutral wire?? Is that normal?

[JohnW2]

Yes I agree I was assuming he was working live, ... My only point was that it is extremely dangerous and in a domestic situation totally uneccessary to work on a live circuit and that one should never assume its dead. ... I have no doubt we all agree that working safely is paramount.

Yes, no argument there. IF he was working live, that is extremely foolish/reckless (aka 'ridiculous/daft') and, as you say, would have been totally unnecessary in the situation concerned.

I was also assuming that a 13 amp appliance was being wired into a radial with no regard as to anything else that may be on that circuit.

As I wrote before, I'm not sure why you regarded this as 'so dangerous'. In terms of what you now say, I don't really understand what you mean by 'with no regard to anything else that may be on that circuit'. Provided the cable is adequately protected, 'what else is connected to the circuit' is of no consequence. It would be theoretically possible to plug at least 100A worth of loads (each with appropriate 13A fuses) into a standard 32A sockets circuit, but that does not make the circuit, per se, 'unsafe'!

Kind Regards, John

 

[DetlefSchmitz]

To answer the question in the thread title...

It is perfectly normal for the neutral wire to have almost exactly the same current as in the line wire, but in the opposite phase.

Hope this helps, but I suspect that this was not the question that the OP intended to ask.

 

[EddieM]

what I mean is if you draw 100 amps through a 2.5mm radial or indeed ring cable, then assuming theres no MCB protection or its faulty (agreed assumptions) then this will be grossly overloading the cable, no?

 

[JohnW2]

what I mean is if you draw 100 amps through a 2.5mm radial or indeed ring cable, then assuming theres no MCB protection or its faulty (agreed assumptions) then this will be grossly overloading the cable, no?

Yes, of course. However, we (you) were talking about a "16A radial", which I take to mean a radial protected by a (non-faulty) 16A MCB. That being the case, 2.5mm² cable (or, indeed, in many cases even 1.5mm² cable) would be adequately protected by that MCB, regardless of what loads were connected (even if they added up to 100A!). It is, of course, not acceptable (or compliant) design practice to have the 'design current' of a circuit (the total of all fixed loads, if it's a fixed-wired circuit) greater than the In ('rating') of the MCB/fuse - but, even if one breaks that rule, the cable will still be adequately protected, provided the MCB/cable combination is correct.

Kind Regards, John

 

[EddieM]

what I mean is if you draw 100 amps through a 2.5mm radial or indeed ring cable, then assuming theres no MCB protection or its faulty (agreed assumptions) then this will be grossly overloading the cable, no?

Yes, of course. However, we (you) were talking about a "16A radial", which I take to mean a radial protected by a (non-faulty) 16A MCB. That being the case, 2.5mm² cable (or, indeed, in many cases even 1.5mm² cable) would be adequately protected by that MCB, regardless of what loads were connected (even if they added up to 100A!). It is, of course, not acceptable (or compliant) design practice to have the 'design current' of a circuit (the total of all fixed loads, if it's a fixed-wired circuit) greater than the In ('rating') of the MCB/fuse - but, even if one breaks that rule, the cable will still be adequately protected, provided the MCB/cable combination is correct.

Kind Regards, John

Yes agreed of course.

 

[JohnW2]

To answer the question in the thread title... It is perfectly normal for the neutral wire to have almost exactly the same current as in the line wire, but in the opposite phase. ... Hope this helps, but I suspect that this was not the question that the OP intended to ask.

I think that we can probably agree that such was probably not the question the OP intended to ask!

However, even if that had been his intention, I think you may need to reconsider your answer - that the current in the N is 'in opposite phase' to that in the L. I think you may be confusing 'phase' with 'physical direction of travel' - if I bent the L conductor into a U-shape, would you say that the currents in the two 'arms' of that 'U' were 180° out-of-phase?

Kind Regards, John

 

[GMan51]

Hi guys,

Sorry, I was working live. Stupid I know now. It won't happen again. I have survived, I'm not dead. But I know that I took a big risk. It won't happen again.

Let's move on..

It was actually in a relative's new house that I was working in. A fairly new build, just a few years old.

The fuse box has a switch saying 'utility spur', that disconnects the power in the utility - I tested it and it does.

There are two white face plates in the utility, one for a tumble dryer and one for a washing machine. That's what they were used for when the previous occupier owned the house. Behind each face plate is connections for live, earth and neutral. And spaces for the appliance wires to go - so the correct wires join together if you know what I mean.

There are no fuses behind either face plate. There's no switch either. The only way to switch the appliance off is to use the controls on the appliances themselves.

So basically, I don't know where the fuse is.

Gareth.

 

[JohnW2]

Sorry, I was working live. Stupid I know now. It won't happen again. I have survived, I'm not dead. But I know that I took a big risk. It won't happen again. Let's move on..

As you say, that's history, but I'm sure you realise that it was plain stupid - and the fact that you survived doesn't meant that you necessarily would if you ever did it again. There are situations in which it is tempting ('for convenience') to work live (even though one really must/should resist that temptation) but it this case it was totally unnecessary - so particularly stupid! Sermon over

The fuse box has a switch saying 'utility spur', that disconnects the power in the utility - I tested it and it does. ... There are two white face plates in the utility, one for a tumble dryer and one for a washing machine. .... Behind each face plate is connections for live, earth and neutral. And spaces for the appliance wires to go - so the correct wires join together if you know what I mean. ... There are no fuses behind either face plate. There's no switch either. The only way to switch the appliance off is to use the controls on the appliances themselves. ... So basically, I don't know where the fuse is.

I imagine that the 'fuse' is probably the "switch in the fusebox saying 'utility spur' " (which is what you probably should have used to avoid working live) - but it sounds as if you have some sort of unusal and unsatisfactory arrangement going on there and I would strongly encourage you to get an electrician to check it out, find out what is going on and do whatever is necessary to make it safe.

Kind Regards, John

 

[EddieM]

Listen to johnw2 sage and courteous advice. Please never work live again!

 

[GMan51]

If you connect the Live of the machine to the Live in the wall and the Live in the wall is switched ON then the Neutral from the machine will be live as it is connected to Live via the electrical items in the machine. When you connect the Neutral from the machine to the Neutral in the wall then it will have a neutral voltage on it.

[1] NEVER work with the power to the circuit still switched ON. ( there are exceptions but NOT for DIYers.

[2] Connect the EARTH first

[3] Connect the Neutral next

[4] Connect the Live last

[5] Switch the power on

Ok - I'll not work live again!!

Does the above quote not explain why the neutral wire was live? Because, as the writer said, I connected the live first, then the earth, then the neutral. (I noticed that the neutral was live before I connected it).

Thanks, Gareth.

 

[ban-all-sheds]

I did not test it for dead. I thought it was a simple case of connecting the three wires together. Is it potentially serious that I did not test this.

Not at all.




Unless you consider death serious.

 

[EddieM]

If you connect the Live of the machine to the Live in the wall and the Live in the wall is switched ON then the Neutral from the machine will be live as it is connected to Live via the electrical items in the machine. When you connect the Neutral from the machine to the Neutral in the wall then it will have a neutral voltage on it.

[1] NEVER work with the power to the circuit still switched ON. ( there are exceptions but NOT for DIYers.

[2] Connect the EARTH first

[3] Connect the Neutral next

[4] Connect the Live last

[5] Switch the power on

Ok - I'll not work live again!!

Does the above quote not explain why the neutral wire was live? Because, as the writer said, I connected the live first, then the earth, then the neutral. (I noticed that the neutral was live before I connected it).

Thanks, Gareth.

Look if you don't know get an electrician in, live flows from to... in layman's terms.

 

[ban-all-sheds]

Up there with all the other horrific things is that he's doing this ignorant and dangerous bumbling about in someone else's house....

 

[DetlefSchmitz]

To answer the question in the thread title... It is perfectly normal for the neutral wire to have almost exactly the same current as in the line wire, but in the opposite phase. ... Hope this helps, but I suspect that this was not the question that the OP intended to ask.

I think that we can probably agree that such was probably not the question the OP intended to ask!

However, even if that had been his intention, I think you may need to reconsider your answer - that the current in the N is 'in opposite phase' to that in the L. I think you may be confusing 'phase' with 'physical direction of travel' - if I bent the L conductor into a U-shape, would you say that the currents in the two 'arms' of that 'U' were 180° out-of-phase?

Kind Regards, John

I think it's something we could argue about all night. If I weren't too tired. But I stand behind the idea that if a a.c. current flows in the opposite direction to another, it is equivalent to a 180 deg phase shift. It's all a matter of frame of reference. But let's not go there.

 

[JohnW2]

Does the above quote not explain why the neutral wire was live? Because, as the writer said, I connected the live first, then the earth, then the neutral. (I noticed that the neutral was live before I connected it).

Yes, it does explain that. However, please take heed of the other things which I and others have said.

Kind Regards, John