TN-S-C problems?

[AusLee]

Hi,

I have to feed a building from my main distribution board. I have sized a breaker an 4C cable accordingly. The cable will be armored so that i will also be providing them with a PE via the metal sheath. From my point of supply till their input the system is a nice TN-S.

The problem is that their input point was previously a service input, and for reason X, the distribution system within that building cannot be known. So i'm thinking that if it's a T system inside or a continuation of the TN-S, i'm fine. But if the distribution inside the building has the N and the PE linked or one and common, my guess is that the breaker i've put for them in the MDB will keep tripping with a Neutral-to-Earth fault. If i don;t send them a PE i might have maintained leakage and hazards.

Is there a way i can make sure the building is supplied, no matter what IEC connection is used inside?

 

[Skogsgurra]

I have a lot of experience with TN-S installations that are not. As soon as a building gets somewhat complex or reaches a certain age, you will inevetably get PE and N mixed up or connected in tens or hundreds of ways. And if you manage to keep the TN-S clean, you can bet that a cooling machine or heat pump eventually connects PE and N. Seen it happen ever so often. TN-S is a nice construct - but extremely difficult to maintain IRL.

Sorry about that.

 

[AusLee]

I agree. The building is a Soviet construct - back from those days. Would you give them the PE and/or install and RCD on your outgoing to protect your systems from faults occuring over thre?