RCD earth potential

[poni]

you can take a horse to water, enough I am out of here!

Why is this so hard? You are all experienced electricians. We had a potential difference between neutral and earth, the thinking was the nail had cut through the installation of the line and was making a connection between line and earth, making the earth live

 

[Stringy75]

You are being attacked, but why? Firstly I would presume that you have not listened to any advise. If you are truly new to the game, then take a deep breath.

My advise is never assume anything, besides the old adage, it really does serve you well in later life. Any fault, intermittent or otherwise can be found, it just takes in depth testing that most people do not do.

For instance I was called out to a school this week that had an intermittent tripping fault, 4 electricians had been previously to try and find the fault. I spent an hour and located a damaged leg on a ring circuit. How?? I tested everything and did some hard dismantling something that the previous guys never did. Am I better than they? not really just more diligent.If you really want to learn never assume that after a couple you know everything, I don't and I am nearly ready for retirement.




 

Thank you very much for your advice. I have listened to advice related to the actual fault, if you look back when polarity was mentioned, I commented that reversed polarity made allot of sense. Most of the other "advise" has just been insults and telling me how wrong and stupid I am

When I go in the field on my own I will most certainly follow your advise and follow the testing procedure straight from the go. It is difficult for a trainee to tell a qualified electrician how to do his job, so for now I will continue to do as I am told and take it all in.

On which side of the isolator was the incorrect termination incoming or outgoing?




 

To be honest I am not sure, I didn't ask

 

[steptoe]

you can take a horse to water, enough I am out of here!

You having a drink @poni :slap

 

[Stringy75]

Stringy,

Think about this please.

How can that happen, IF, the installation, and supply are correctly wired, without operating a protective device?




 

It was noted the RCD did not trip, there would have been a leakage current from line to earth, if greater than 30mA, the RCD should have tripped. I dont think necessarily the MCB would trip, this would depend upon the resistance between the bridge the nail was making and the value of Zs

 

[steptoe]

On which side of the isolator was the incorrect termination incoming or outgoing?

That's fairly irrelevant IMO,

Always verify polarity before you connect something, then verify again before energising 

 

[Sharpend]

That's fairly irrelevant IMO,

Always verify polarity before you connect something, then verify again before energising 

I agree, I was merely trying to establish whether this was a result of meter monkey or installer. However it was irrelevant as stringy unfortunately did not know the answer himself

 

[Stringy75]

which one of you would have spotted if you had done a Ze when you started or shortly after. I'm STILL confused as to why you were there .....

I've just come in from an evening call out - the call out was due to a "noisy" fuseboard. After checking ALL the connections inside, and finding the incoming neutral very loose, I then checked the Ze. This confirmed the polarity and the quality of the suppliers earth. Simples.




 

If you think Ze confirms polarity you need locking up

 

[Doc Hudson]

Why is this so hard? You are all experienced electricians. We had a potential difference between neutral and earth, the thinking was the nail had cut through the installation of the line and was making a connection between line and earth, making the earth live

Possibly because if you go back and read GN3 polarity is a fundamental part of both dead and live testing. the symptoms you suggest with a nail, do not match anything you have described. e.g. 230v between N & E when earth continuity has been verified back to the MET. I cannot believe that three others plus yourself do not have enough noggin to figure out that a reading of 230v N-E and 0v L-E is a sure fire sign of reversed polarity. Even a basic plug in polarity tester would have shown this. http://www.screwfix.com/p/lap-ms6860d-socket-tester/91596  only £10 may save you hours of wasted work and return visits.  (£2.50 each if the four of you chip in and share one)

Doc H. 

If you think Ze confirms polarity you need locking up

You probably need to invest in a better meter then, as I know mine will indicate reversed polarity once I put the correct probes onto L N & E.

Doc H.

 

[Stringy75]

Some of you seem to want to discuss electrical stuff and offer helpful advise. A question to thoes people, is it just me, or do you think there are some people who come in here just  to troll others?

 

[Murdoch]

Mine won't do the test if you connect the leads to the incorrect terminals, and it won't test if there isn't a live, or a neutral or an earth. It needs all 3 to work

 

[Manator]

Go to bed, it is far past your comfort zone. Your not a troll, just a light hearted amusement.

 

[Stringy75]

Possibly because if you go back and read GN3 polarity is a fundamental part of both dead and live testing. the symptoms you suggest with a nail, do not match anything you have described. e.g. 230v between N & E when earth continuity has been verified back to the MET. I cannot believe that three others plus yourself do not have enough noggin to figure out that a reading of 230v N-E and 0v L-E is a sure fire sign of reversed polarity. Even a basic plug in polarity tester would have shown this. http://www.screwfix.com/p/lap-ms6860d-socket-tester/91596  only £10 may save you hours of wasted work and return visits.  (£2.50 each if the four of you chip in and share one)

Doc H. 

You probably need to invest in a better meter then, as I know mine will indicate reversed polarity once I put the correct probes onto L N & E.

Doc H.




 

Testing Ze does not prove polarity, Ze is the resistance of the incoming earth. Dead testing is not just testing the resistance of the incoming earth. The continuity dead tests prove polarity of the internal circuits  and the polarity live test proves the polarity of the incoming supply. You are really embarrassing yourselves

 

[Sharpend]

Some of you seem to want to discuss electrical stuff and offer helpful advise. A question to thoes people, is it just me, or do you think there are some people who come in here just  to troll others?

I would have to disagree with your question here, when you attend the forum regularly you will gain knowledge of the individuals and the essence and tone of their personalities which shines through in their posts. It is fair to say that some are more direct than others, some more eloquent than others and this clearly picked up by new comers and often misinterpreted for aggression, negative, etc however I can assure you aggression I don't tolerate and I've been here a while, so I'd generally say that the majority of members are very willing to help and probably nice people outside of the forum. 

 

[Stringy75]

Put your multifunction tester onto volts, and hold the probes on the incoming terminals of the main switch on the consumer unit. Look to see if L and N are indicated as correct on the display 

I would have to disagree with your question here, when you attend the forum regularly you will gain knowledge of the individuals and the essence and tone of their personalities which shines through in their posts. It is fair to say that some are more direct than others, some more eloquent than others and this clearly picked up by new comers and often misinterpreted for aggression, negative, etc however I can assure you aggression I don't tolerate and I've been here a while, so I'd generally say that the majority of members are very willing to help and probably nice people outside of the forum. 




 

Thank you for the heads up

 

[Sharpend]

Put your multifunction tester onto volts, and hold the probes on the incoming terminals of the main switch on the consumer unit. Look to see if L and N are indicated as correct on the display 

Yes you can test polarity by voltage measurements, as your tester will tell you if leads are incorrect, similarly your tester tells you the same thing when you do a Ze test.

 

[Stringy75]

Yes you can test polarity by voltage measurements, as your tester will tell you if leads are incorrect, similarly your tester tells you the same thing when you do a Ze test.




 

Ok I am sorry for saying he needs locking up then, I am new to testing, I tested for polarity using the method I outlined. I will see if my tester indicates polarity tomorrow, I had not noticed that before. I thought they were trolling me

 

[Stringy75]

Thinking about it if polarity is not correct you would not have a voltage when you touch the probe on the incoming line, so you could not do the test. This is not the recommended live polarity test though

 

[Sharpend]

Please do and report back your findings, what tester do you use?

I'll accept your apologies on behalf of our esteemed colleagues. 

I glad that you are now recognising that perhaps it was your approach that inflamed others, it's an important skill to recognise going forward in life.

you will gain more respect if you continue in this vein. 

 

[steptoe]

Testing Ze does not prove polarity, Ze is the resistance of the incoming earth. Dead testing is not just testing the resistance of the incoming earth. The continuity dead tests prove polarity of the internal circuits  and the polarity live test proves the polarity of the incoming supply. You are really embarrassing yourselves

Ze does NOT measure the RESISTANCE of the suppliers earth,

have a look at the definitions part of the big (whatevercolouritisthisweek) comic

Terms and definitions are VERY VERY important,

Surely getting 41/50 you should know this?

 

[Sharpend]

Thinking about it if polarity is not correct you would not have a voltage when you touch the probe on the incoming line, so you could not do the test. This is not the recommended live polarity test though

The mere fact that your tester will not do the test, should indicate to you that something is wrong, fortunately with the tester indicating the problem you do not need to test for polarity unless you wish to confirm the testers indications.