Sub main

[Griffin]

Hi All,

Just a quickie,

On a job at the mo. A replacement c/u , rewire shower and some sockets etc.

The c/u is near the kitchen fed by a 16mm t+e sub main. The sub is fed from a switch fuse in the hall way. Prior to the switch fuse is a older 100ma RCD. you know the big grey and black fellas.

My question is should i leave the older RCD in to protect the sub (subject to test). The c/u will have 2 30ma RCD's installed so discrimination will be ok.

Should I remove or leave it if it checks out ok.

Feedback welcome

G

 

[Griffin]

Someone must have an opinion

G

 

[trix]

Not a bad plan G.

As it's an existing sub, no problems with rcd.

The 100ma covers a few extra's.

Best do a periodic first.

 

[Guest123]

There wont be any discrimination between the 100mA RCD and the 2 30mA RCD's in the CU......unless it's a time delayed "S" type one.

Depending on how the sub-main is installed it may need RCD protection of the 30mA variety though.

 

[Griffin]

Thanks Chaps,

Lenny could you elaborate please. What is the criteria

Many Thanks

G

 

[Guest123]

Ok, if the T+E sub is buried in the wall less than 50mm and not in earthed mateallic conduit etc etc then it will need additional protection by 30mA RCD.

If it's surface run in it's entireity though in pvc trunking for instance, then it would not need the additional 30mA protection. If it's a TT system though then it would need an RCD up front regardless of install method i.e a 100A 100mA time delayed type.

 

[Griffin]

Thanks Mate.

It is a TT. So I will change it out for an 'S' type RCD

Regards

G

 

[Guest123]

Happy days.

 

[pennywise]

Happy days until you see the cost of a time delay RCD manufacturers really take the Mick With the prices