Testing Problems

[needasparks]

Hi Guys,
Had a strange issue i have never come across on a domestic job before and made testing a nightmare.
Was a couple of new circuits in a bathroom, new CU and earthing upgrade gas/water, new blah, blah, blah.
Did some quick continuity and IR checks prior to the CU change all came out ok so ripped the old out and in with the new one.
Went to do final testing and meter will not earth loop Ze or any Zs readings. Meter comes up with error 5 every time and will not test, now up till now whenever this happens it usually means neutral missing so head scratching started, checked meter instruction book (felt a bit of a girl at this point, no real man reads instructions) and error 5 in noisy earth, thought this a bit strange as this was a council estate and no where near industrial areas so checked with Fluke uk and they confirmed this. told me how to get round the noisy earth problem when testing so sorted.
Still cannot understand how these houses can suffer such a problem. any ideas ?

 

[Octopus]

Did you do a Ze before you started?

 

[needasparks]

Did you do a Ze before you started?

Don't be clever ......

 

[Octopus]

Don't be clever ......

Not being clever!!!

 

[AP Electrical]

How did you get round the ERR5 in the end ? - out of intrest - had it myself

 

[Jabbajaws]

Have you ruled the meter being itself faulty by getting a successful Ze/Zs reading elsewhere? (as in not the place you are currently working).

 

[needasparks]

Must admit i've never come up against this before. Yes, can understand it in a idustrial location but not here.
So my point is How can a housing estate suffer with this type of issue.

 

[needasparks]

How did you get round the ERR5 in the end ? - out of intrest - had it myself

after you get error 5 press down on the scroll button and the reading comes up.

 

[needasparks]

Have you ruled the meter being itself faulty by getting a successful Ze/Zs reading elsewhere? (as in not the place you are currently working).

See what your saying, and TBH did not even think of the meter being an issue.

Should have given the supply also really. Its a TN-S supply cable installed about 1954 so the owners said, quite an old service head, old yellow box jobbie, still good condition for its age though.

 

[i=p/u]

you could of caalculated it with max values of ze...... but suppose just another why is this happening..

 

[needasparks]

you could of caalculated it with max values of ze...... but suppose just another why is this happening..

How can you calculate Zs and Ze just from an assumption on supply, not very proffessional.
In saying that, I now know how to use meter in this situation.
Which brings another question, do other meters suffer this problem or are most people unaware of this at an installation.


Is this something to just ignore or inform DNO. ?

 

[i=p/u]

well you could of used max ze value and just take your reading on R1+R2 and add together..... but i see you point a strange one..

 

[MarkieSparkie]

after you get error 5 press down on the scroll button and the reading comes up.

You are correct it will give you a reading, but you cannot rely on it being accurate because the high noise threshold may have corrupted the measurement.

 

[MarkieSparkie]

How can you calculate Zs and Ze just from an assumption on supply, not very proffessional.
In saying that, I now know how to use meter in this situation.
Which brings another question, do other meters suffer this problem or are most people unaware of this at an installation.

Is this something to just ignore or inform DNO. ?

The only MFTs that are fairly immune to high noise are the Meggers due to the averaged multiple measurement technique employed. Megger users rarely see a high noise warning, I see an average of one a year, all of those have been in known high noise industrial areas.

If you inform the DNO I doubt they will take action, they will probably just pass the buck, saying it's your clients responsibility. You will be lucky if you can get them to formally test or monitor the supply let alone the local network, but we live in hope.

 

[Engineer54]

This phenomenon, relates back to other threads here on the forum on the need for ''Clean Earths''!!

This is a perfect example of why a real clean earth system is often employed where noisy/dirty earthing is known to exist. Also why you tend to find the bigger IT processing facilities are located away from heavy industrial areas/parks and the like...