DNO Problems (Yorkshire)

[Springerflame]

Hi guys (being new to this, I hope I phrase the question right)

Has anyone had any problems getting a Ze value from YEDL. I work in a school and its a no brainer when it comes to testing Ze. There is no way I would disconnect the main earth to do this test whilst the kids are in school. As we are also a community sports facility, so the evenings and weekends are out as well. I have spoken to YEDL and asked them for this information, but they have fobbed me off with:

"We can come check it for

 

[m4tty]

Cant you just check the earthing and use the worst case scenario figure i.e. TNCS 0.35 or TNS 0.80 ?

May be wrong so I will apply my hard hat

Cheers

 

[batty]

What is the earthing system? as long as its not TT you can check it with everthing connected as far as I am concearned. If it is TT and you have metal service pipes you could probably disconnect main earth to rod to test it as the water pipe will probably be what brings it down anyway.

 

[a1]

Welcome to the forum

Ze=Zs-(R1+R2)

?

 

[Springerflame]

Thanks guys. It's a TNCs system. I dont want to hold up the job, so I was already working along the lines of what is says in the regs. I just wondered if anyone else was having a problem.

Someone mentioned doing the test with everything connected, but its not something I have ever come across, being a noob and all ?:|

Alan

 

[Andy™]

prob best to assume 0.35, and measure Zdb, making a note that all bonding was connected

obviously, if you get higher than 0.35, then there is something wrong

 

[Lurch]

Welcome to the forumZe=Zs-(R1+R2)

?

No, as your Zs will include parallel paths so hypothetically Ze could be 120 ohms on a TN-C-S service but the water pipe brings the Zs down to .2 ohms, and R1+R2 is .1 ohms so by your formula Ze is .1 ohms, but it's not.

 

[batty]

But if its TN-C-S earth fault loop will be roughly the same as L-N loop surely.

 

[Lurch]

But if its TN-C-S earth fault loop will be roughly the same as L-N loop surely.

It should be, but this is why you should test it.

The above was just a theoretical scenario anyway, wasn;t saying anything more or less than that.

 

[SPECIAL LOCATION]

Hi guys (being new to this, I hope I phrase the question right)Has anyone had any problems getting a Ze value from YEDL. I work in a school and its a no brainer when it comes to testing Ze. There is no way I would disconnect the main earth to do this test whilst the kids are in school. As we are also a community sports facility, so the evenings and weekends are out as well. I have spoken to YEDL and asked them for this information, but they have fobbed me off with:

"We can come check it for

 

[binky]

There is no way I would disconnect the main earth to do this test whilst the kids are in school. ....... What are they gonna do, that I cant do ?

It will be for 1 minute max, main bonding is still in place should someone have an accident at exactly the same time - I think you are over worrying about the level of risk. Its exactly what YEDL will do.

You could however disconnect bonding and take Zs or Ze reading if you are that woried about an accident occurring whilst testing the installation. Failing that you will have to do this test out of hours. Wouldn't bother with DNO personnally, it will take more time and hassle than its worth :^O

 

[Andy™]

Regulation 28 of the ESQCR 2002 requires distributors to provide the following information to relevant persons FREE OFF CHARGE!

• Max PSC @ supply terminals
  
• Max Earth Loop impedance of the earth fault path outside of the installation(Ze)
  
• etc...
  
• etc...
  
• etc...
  

all they have to say it '0.35 ohms'

 

[Springerflame]

Guys

I thank you for your assistance. I have been, seen and done the job, and used the value given in the regs and on here so all should now be good

Thanks for the advice, because its nice to get some pointers when you are a noob and worried you might make a right mess of it

Al ut the kettle on

 

[mikep]

Arrange to go in at 3am when all are at home asleep

ZZZZZZZZZZZZZZZZZZZZZZZZ.............