Earthing system

[Jay Sparks]

I have come accross an earthing system that im not to sure about. On the main incoming cable it has an earthing clamp fastened to the cable shroud, from this is some 16mm earth cable that goes in to the main cut out housing then comes back out and up into the ccu. In the OSG it shows a TN-S system that has a clamp with an earth cable that goes to an earth block. The TN-C-S system shows the earth cable coming out of the cut out housing and going into an earth block. The system ive come accross seems to do both.
So can any one tell me what it is. Or is it that obvious and Im just thick.

Cheers

 

[cagedanimal2010]

what is the ze reading?

 

[GrannySmiff]

Does it go to an MET after the shroud? otherwise it sounds odd, why would a tns go back to the cut out and what would it terminate to?.

Do you have any pics?.

 

[Sintra]

Test Ze then test loop impedance of L - N at origin if the readings are the same then it's TNC-S.

 

[GrannySmiff]

Is that a hard and fast rule? that could be quite handy to remember.

 

[JulianC]

Saw one once that was a TN-C-S system with what was presumably a bonding connection to the metallic outer sheath of the incoming cable (extraneous conductive part I s'pose). Could this be something similar?

 

[Sintra]

Is that a hard and fast rule? that could be quite handy to remember.

Yes in a TNC-S the N & E are joined in the service head so the results for both will be the same were in a TN-S they are seperate so you would expect the L - E reading to be higher than L - N.

 

[andekoch]

came across one of these the other day and it was tns. the 'met' was part of the fuse head (as per the op) as opposed to an externally mounted and visible.

always nice whn the dno simply puts on a bonding clamp for their main earth as opposed to a more secure swaggered (i think that is spelt correctly) on connection.

 

[Jay Sparks]

Cheers lads. The met is inside the cut out i think as there wasnt one on the out side. I cant do any readings on it as I was doing a quote at the time so not sure if ill get the job but just wanted to know what you guys thought it was so next time I would know.

Cheers