I was thinking.......

[Dave2010]

If you have a TT supply 16th edition board that has a 100A 100mA types-s rcd main switch and you wanna work on a lighting circuit that is on the side of this main switch (not protected by the 30mA RCD) do you have to either:

* move the light MCB over to the 30mA RCD side or,
* change the MCB to a RCBO or
* nothing can you just leave as is

just looking for little clarification

cheers peeps

 

[Chri5]

Per 17th MCB's shoulkd be protected by 30ma unless you can confirm the wiring is >50mm depth in chases and along route.

The 100ma is a TT requirement, but per isn't suitable as 'local' protection

 

[GaryMo]

You could always look into the other options from 522.6.6

 

[Jacobssi]

Change to an rcbo us stated in 17th unless it's less more than50mm into the wall

 

[GaryMo]

Change to an rcbo us stated in 17th unless it's less more than50mm into the wall

I'm not sure what you wrote there but are you saying the '17th' states to use an RCBO?

 

[bongos]

If you have a TT supply 16th edition board that has a 100A 100mA types-s rcd main switch and you wanna work on a lighting circuit that is on the side of this main switch (not protected by the 30mA RCD)

When you say work do you mean replace fittings etc? In this case isolate the lighting circuit with the respective MCB.

Or are you meaning you are wanting to extend the circuit and are asking advice as to the best way to provide 30mA RCD protection?

 

[mfarrow]

isolate the lighting circuit with the respective MCB.

in a TT or IT installation, all live conductors must be disconnected for proper isolation. I'm not sure whether or where this is given in the original publication of BS7671:2008, but it is included in the corrigendum as a note to Table 53.2.

 

[bongos]

I'm not sure whether or where this is given in the original publication of BS7671:2008, but it is included in the corrigendum as a note to Table 53.2.

537.2.1.1 makes reference to every circuit being capable of being isolated from each live supply conductor (excluding TN systems) but I was still meaning in what sense the OP meant this...

If you have a TT supply 16th edition board that has a 100A 100mA types-s rcd main switch and you wanna work on a lighting circuit that is on the side of this main switch (not protected by the 30mA RCD)

 

[GaryMo]

I took his description of 'working on' to mean an addition or alteration but I'm sure he'll clarify.

 

[Spark123]

I think I have only ever come across one IT installation in my days of sparkying, not a very common system at all.

 

[Jacobssi]

Change to an rcbo us stated in 17th unless it's less more than50mm into the wall

I'm not sure what you wrote there but are you saying the '17th' states to use an RCBO?

sorry mcb my mind was elsewhere

 

[Dave2010]

morning guys

yeah i meant extending the circuit by 1 fitting (going up into the loft for example)

cheers

 

[ban-all-sheds]

Will you end up with new cabling concealed <50mm deep in a wall or partition?

 

[Dave2010]

only place cable will be concealed is under boards on loft floor, would be then clipped direct up to the fitting.

 

[ban-all-sheds]

Don't need to add any RCD protection then.