Ze and continuity on a ring final

[Sjn electrical]

Hi all

Just a phone call from a potential customer who is after a periodic but has mentioned equipment that cant be turned off.

How would i do a proper 'Ze' and a continuity test to a ring final circuit?
(if the equipment is on a ring final)

I have been told if you cant turn a circuit off it is ok to calculate the R1 + R2, is this true?

Am new to the world of testing so any help would be great.

Thanks Steven

 

[Octopus]

LIM (Limitation)?

Either the customer accepts the limitation or allows you access, out of hours (at extra cost) to undertake the test.

Thats what I think, I'm sure others will contribute!

 

[Sjn electrical]

Hi Murdoch,
So its defonatly not acceptable to do a Ze with the main earth still connected?
Will the values i get from doing a continuity test reflect from other results? (if you understand my bad termanology)

 

[mattmoo1974]

If you do it with it connected you ll get parallel paths and a lower reading.
On that note does any 1 know why you dont take the reading like that?

 

[Deleted member 26818]

A Ze test with the main earth still connected, would be termed Zdb.
You are allowed to record the Ze of an installation by mesurement, or by enquiry. Enquiry, would most probablly entail the DNO informing you of the standard values 0.35Ω for TN-S and 0.8Ω for TN-C-S.
R1 + R2 is not actually required for a PIR, as for calculating it, unless you know the exact circuit length then you will just be guessing.
Best bet would be to do a Zs test at each point of utilisation.

 

[Sparky Ninja]

R1&R2 must not be calculated.

 

[SirKit Breaker]

Hi all

Just a phone call from a potential customer who is after a periodic but has mentioned equipment that cant be turned off.

How would i do a proper 'Ze' and a continuity test to a ring final circuit?
(if the equipment is on a ring final)

I have been told if you cant turn a circuit off it is ok to calculate the R1 + R2, is this true?

Am new to the world of testing so any help would be great.

Thanks Steven

If you are new and inexperienced with test and inspection, then reading Guidance note 3 is a must. I would also be trying to find someone who can help you on the job as well to help you find your feet. You are going to sign a legal document once you have finished, and this WILL be used to beat you with if something goes pete tong. I also agree with what Murdoch has said.

What part of the country are you in, i have a bit of free time in the near future, and dont mind giving you an hour or 3.

Cheers..........howard

 

[Sjn electrical]

If you are new and inexperienced with test and inspection, then reading Guidance note 3 is a must. I would also be trying to find someone who can help you on the job as well to help you find your feet. You are going to sign a legal document once you have finished, and this WILL be used to beat you with if something goes pete tong. I also agree with what Murdoch has said.

What part of the country are you in, i have a bit of free time in the near future, and dont mind giving you an hour or 3.

Cheers..........howard

Hi Howard,
Thats really really good of you to offer your time.
I have other sparks i normal harass when im in trouble but wanted to know what other people thought before i took the job on.

Steven

 

[sparks_114]

A Ze test with the main earth still connected, would be termed Zdb.
You are allowed to record the Ze of an installation by mesurement, or by enquiry. Enquiry, would most probablly entail the DNO informing you of the standard values 0.35Ω for TN-S and 0.8Ω for TN-C-S.
R1 + R2 is not actually required for a PIR, as for calculating it, unless you know the exact circuit length then you will just be guessing.
Best bet would be to do a Zs test at each point of utilisation.

Good stuff spinlondon, small correction: 0.80Ω for TN-S and 0.035Ω for for TN-C-S.

 

[keniff]

I think spins right 0.35? But tncs

 

[Deleted member 26818]

Yes the values are correct, just the wrong way round.
Although, you never can tell with DNOs.