Three Phase overhead supply is it TN C

[Michael J]

While carrying out a EICR I found on first inspection that there were no RCDs installed . When I checked at the Pole Mounted Transformer the Earth & Neutral were connected at the Neutral point. So am I right in concluding it's a TN-C System? The 17th Edition states that RCDs should not be installed where a TN C System is used (411.4.4)

 

[buzzlightyear]

Are you sure it is tncs on the pole or TT.what is in the property?.
got any pic of the board .

 

[Michael J]

I will take a pic tomorrow,but it looks like the Earth and Neutral are connected at the transfer. The reason I am suspecting is a TN-C is the lack of RCD protection on the Ring main final circuits. If it was a TT it would be protected with RCD at the mains

 

[buzzlightyear]

you mean up front RcD Before the main switch .

 

[Michael J]

Yes, or any final circuit in the building, by the way it feeds a hotel. The overhead feed is by way of bundle conductors (4) sorry that's a South African term. I don't know what you call them here?

 

[buzzlightyear]

is it three phase to the buiding.

 

[Silly Sausage]

411.4.4

Eh?
The 17th Edition states that RCDs should not be installed where a TN C System is used 411.4.4

The following types of protective device may be used for fault protection:
(i) An overcurrent protective device
(ii) An RCD.

It'll be a PME supply. Concentric cable split at the installation intake, to N & E.

 

[Michael J]

Eh?
The 17th Edition states that RCDs should not be installed where a TN C System is used 411.4.4

The following types of protective device may be used for fault protection:
(i) An overcurrent protective device
(ii) An RCD.

It'll be a PME supply. Concentric cable split at the installation intake, to N & E.

Read on a couple of lines after Note 1
"An RCD Shat be used in a TN-C system"

 

[Michael J]

Sorry guys it's late it should read " An RCD Shall not be used in a TN_C system"

 

[Michael J]

is it three phase to the buiding.

Yes it is

 

[Silly Sausage]

Yes it is

I think you might be getting confused here chief, TNC is NOT allowed within an installation. TNC/PME supply, then the Earth is split off at the intake.

 

[Strima]

That'll be 414.4.5 for no RCD on TN-C?

 

[buzzlightyear]

Yes it is

take pic for us in the main intake at the hotel.

 

[buzzlightyear]

Strima are you not counting sheep in your bed .LoL .because im in night garden with iggle piggle.

 

[Michael J]

I think you might be getting confused here chief, TNC is NOT allowed within an installation. TNC/PME supply, then the Earth is split off at the intake.

Thanks, I will take a closer look at the intake, I just don't understand why there are no RCDs on the final ring circuits this hotel has 6 DBs

 

[static zap]

..... in night garden with iggle piggle.

...I'l be suffering Red Wine ..piddle .. Watering them earth rods !
( DNO ..where they are ..)

 

[streamer]

The lack of RCDs is probably more to do with the age of the installation than the supply type.

 

[Darkwood]

My house has a two wire supply coming in along the outside wall, it was clearly a TT in the past but has been converted to TNC even though the supply is via 2 individual separate single cores.
The DNO risk access any existing TT before conversion I am led to believe, I see no reason why your install won't have been converted at some point even an overhead supply.

 

[Strima]

Strima are you not counting sheep in your bed .LoL .because im in night garden with iggle piggle.

A people said the Magic Roundabout was messed up...

 

[westward10]

You probably have TN-C external to the building then the PEN conductor is separated at the service head which gives the S on TN-C-S.