PME & TNS supply in same building

[interlude]

Hello all,

Have been doing some work in a large building complex, the original building has a TNS supply but the large extension to the building has a seperate PME supply.

At present there are no main protective bonding conductors to water/gas/oil and these services are common to both old and new parts of the building. If these MPB conductors are taken to one of the origins (PME for example) I'm imagining that will cause issues by mixing two Earth potentials (PME potential on pipe work and TNS potential from cpc's). Have been looking through the BGB but can't find an answer to my question. Any ideas?

 

[Knobhead]

Re: TNCS & TNS supply in same building

Don’t make it look like that was a quote from me.

 

[netblindpaul]

Re: TNCS & TNS supply in same building

Sorry, typo, I hope it is corrected now!
Sorry.

 

[interlude]

Re: TNCS & TNS supply in same building

The tread title says something altogether different ? ? ? ?


I give up!

Yes you are correct it does, have corrected any confusion in my above post mind.

 

[netblindpaul]

Re: TNCS & TNS supply in same building

So you have a PME supply & a TN-S supply in the same building?
Do the DNO know about this?
Or, have there been building changes since the supplies were installed?

 

[Knobhead]

Re: TNCS & TNS supply in same building

Thank god I’ve been and picked my painkillers up today, I need them.

 

[Marvo]

I've changed the thread title to avoid confusion. I'm very surprised the supply authority would mix these two earthing arrangements in the same building.

 

[Engineer54]

So i wonder what happens when say a TN-S branch joint goes down and the DNO rather than repair the joint converts it to a TNC-S supply. You now have say a row of TN-S supplied houses with one or more with a TNC-S supply. All of whom are using common metal water and gas mains which will in turn be bonded at each properties electrical MET??

Problem??

 

[davesparks]

Is that not the reason for bonding being the size it is, to cope with circulating/diverted currents arising from that situation?
And why undersized bonding should be assessed for signs of thermal damage.