TN-C or TN-C-S

[Test Probes]

Hi. Can any one clear some thing up with my schedule of test results for form? The situation is this. I'm testing a building with TN-C-S coming into the switch room. The earthing arrangement being used for the DB's coming out of the main switch gear is TN-S. When filling out the schedule of test result form, do I tick TN-C-S for the main system or TN-S for the earthing arrangement?

 

[High Tower]

It's TNC-S it cannot possibly change, it is combined up until the in comer but then seperates from there, that is the definition ofTNC-s!!, it's not possible for the arrangement to change.

Don't forget your arrangent is relevant to your ZE, however post switch room it becomes ZDB and simply forms part of the R1&R2 part of your earth fault loop path .

 

[drew35]

Err what? Sorry? Pardon?

Ditto what High Tower said.

 

[Test Probes]

Thanks guys. That is what i thought as well.:smile5:

 

[High Tower]

Splendid!

 

[Engineer54]

Hi. Can any one clear some thing up with my schedule of test results for form? The situation is this. I'm testing a building with TN-C-S coming into the switch room. The earthing arrangement being used for the DB's coming out of the main switch gear is TN-S. When filling out the schedule of test result form, do I tick TN-C-S for the main system or TN-S for the earthing arrangement?

As PME/TNC-S provides you with (for want of a better word) an ''artificial'' earthing point, that earthing arrangement will remain the same throughout the installation as a whole. The N-E connection will only be present at the at the DNO's incoming service head.

Now, is your supply to the Main Switch room coming from an on-site MV/LV distribution TX?? If it is, then you will probably looking at a TN-S earthing arrangement. What you could be looking at within the Main Switchboard, is the TX neutral earthing point!! It can get a little confusing for those that don't have larger project experience... lol!!

 

[tony mc]

A picture woul be good if you have one !

 

[Test Probes]

Hi Toni mc. I know the main switch gear and the local energy supplier have installed TN-C-S. But when the DB's are supplied with an armour cable with the armour being the earthing conductor, does this now make the DB's TN-C or is the whole system TN-C-S? ie switch room and DB's installed into the system.

 

[Marnik]

It's the incoming arrangement wich denotes the type of earthing, ie if the service head is TN-C-S then that is what goes down on the Cert

 

[Test Probes]

Hi marnik. Nice simple reply. This is what I had thought but just wanted some clarification. Many thanks.