Its a trickster...

[cliffed]

Adding a couple of power points to existing ring main the cabling is Pvc T&E 2.5mm/1.00mm.
Anyone have problems with this, its a TT System,Zs 11.49 ohms.
RCD 30ma...32 amp 60898 B type.

 

[westward10]

What sort of problems.

 

[Pretty Mouth]

I believe the problem with a 1.0mm CPC on a ring final is if it is protected by a 30A rewireable fuse. A fault current high enough to blow the fuse in the required time will mean a thicker CPC is required regarding adiabatic requirements. This shouldn't be a problem for an MCB

 

[telectrix]

but with a Zs of 11. 49 Ω, he's only going to get a fault current of around 21A. so the MCB is never going to trip. he;s relying on the RCD for fault protection. the RCD will trip long before the 1.0mm cpc even knows about it. a bit like Pearl Harbour in 1941.

 

[littlespark]

Pearl Harbour? Is that one of your ex girlfriends, tel?

 

[cliffed]

but with a Zs of 11. 49 Ω, he's only going to get a fault current of around 21A. so the MCB is never going to trip. he;s relying on the RCD for fault protection. the RCD will trip long before the 1.0mm cpc even knows about it. a bit like Pearl Harbour in 1941.we are relying on earth fault protection only.

Thats the earth fault current so ok now a short circuit fault may be a problem.
With a High resistance ,& low current on the Live & neutral may be a problem on the mcb tripping.

 

[westward10]

Why would you have a "high" resistance between line and neutral.

 

[pc1966]

With a High resistance ,& low current on the Live & neutral may be a problem on the mcb tripping.

Not if it meets the volt-drop requirements! What is the PSSC on it?

 

[loz2754]

Thats the earth fault current so ok now a short circuit fault may be a problem.
With a High resistance ,& low current on the Live & neutral may be a problem on the mcb tripping.

There was a recent thread on the subject of TT L-N fault protection, in which @Julie. makes some very interesting and valid arguments:

Just wondering

What would you put-in the EIC column for Max Loop reading permitted for a TT system, for a 32 amp 60898. Protected by Rcd 30ma,Dual split DB.

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