FARM INSTALLATION- First Time

[Piratepete]

Hi Lenny
May I clarify that the posts 19 and 20 relate to the earlier discussion about the use of 3 pole or 4 pole main isolators and are not an answer to my question on Single Pole RCBOs in post 20!
Pete

 

[Specialist]

They are, yes. But, the impedance of the earth path on a TT system from the installation end back to the supply Tx, can be extremely high as it is via the general mass of earth.

Also, in a TT system, the impedance between the MET and the general mass of earth (via the MEC & earth electrode(s)) and consequently the star point of the supply transformer can be very high (20ohms). In TN-S and TN-C-S this impedance is much lower (0.8 & 0.35ohms respectively) because the MET is directly connected to the star point of the transformer via the supplied earth or neutral conductors.

:clap:Lenny I've gotta be fair to you mate, the way you answer peoples questions Rocks. :icon4:

 

[Chr!s]

Hi Hasel5



What about them?

The Main DB is on a TN-C-S supply so sp rcbos protecting sockets is OK.

So the question is - is a single pole (only the live is switched but both poles sensed) rcbo acceptable for protecting a sub board which is TT?

Cheers
Pete

Yes, its acceptable to use a Rcbo for protecting a TT circuit in some instances.

Regards Chris