safety device for distribution circuit!

[yellowvanman]

There is no mention of a 100mA time delayed RCD in the 17th, except in Appendix 3 (Page 243) to give disconnection times. Its used as a solution for RCD discrimination, whereby the RCD closest to the fault will trip before anything else trips. The time delay gives a 30mA RCD 100ms to trip, if not it trips itself.
A 30mA RCD should trip within 300ms for a 30mA fault (which wouldn't disturb the 100mA RCD), or the 30mA RCD should trip within 150ms for a 60mA (x2) fault, so this could make the 100ms RCD react, but for a 150mA (x5) fault the 30mA RCD should definetly trip within 40ms, if not the 100mA should trip!

RCDs outside Additional protection and the other requirements of a 30mA RCD are used when the potential fault current is not enough to trip an overcurrent device (eg. fuse or MCB)

 

[nickblake]

All final circuits up to 32A are 0.4s, all circuits above 32A AND DISTRIBUTION CIRCUITS are 5s, therefore all distribution circuits reagrdless of size are 5s......... have look at the table.
only mentioned a 100mA RCD incase it was a TT system, and that would be the only reason you must have an RCD protecting the distribution circuit....... and yes i know the disconnection time is not 5s for TT.

Yes i agree i had it in my mind it was a final circuit how ever not all distribution circuits have a 5 second disconnection time , hence the reason why i asked for further information , i was unaware of the CDU in the shed type wether it had an RCD if it had no RCD and supplied Socket outlets it would then be required to disconnect in .4 of a second and require RCD protection

 

[Martin Bradley]

IQ you would not, and i know you know, but people fail to read things.I dont think they have cotton on to what you have said. unless im reading it wrong LOL.

 

[mart8235]

Yes i agree i had it in my mind it was a final circuit how ever not all distribution circuits have a 5 second disconnection time , hence the reason why i asked for further information , i was unaware of the CDU in the shed type wether it had an RCD if it had no RCD and supplied Socket outlets it would then be required to disconnect in .4 of a second and require RCD protection

isn't the Dist board in the garage a separate issue? All those circuits would need to be considered separately? with the most likely answer being RCD main switch or RCBO's in the garage DB.

And guys,
what i was originally saying is that there is no requirement for the distribution circuit to be on an RCD/RCBO provided the cable is adequately protected.
As for suggesting that a TT system should (NOT MUST - big difference between the wording) be on a 100mA RCD then obviously I'm unaware that's the worst thing you can do? only trying to cover the bases!

IQ Electrical what would YOU install on a TT System?
PLEASE STOP SHOUT TYPING AT ME!!!!! I'll tell my mum!!!!

 

[IQ Electrical]

It was the highlighted text in post 6, the word you used was 'must'-check it out.

I just don't want anyone reading the thread to assume that the 100mA front end rcd is the in stone TT setup.

The introduction of BS7671:2008 virtually eliminated the need for the above scenario.

I put '17th edition' consumer unit in inverted comma's to show that the terminology was incorrect but to save describing it's setup.

No more shout typing so don't disturb your mum

 

[Deleted member 26818]

Shouldn't you use the term '(sic)' when indicating something is incorrect?

 

[IQ Electrical]

Shouldn't you use the term '(sic)' when indicating something is incorrect?

You certainly should.

 

[morph]

Im with IQ on this one you cant say that the disconnection time is 5 seconds as you dont know the size of the protective device !!! all circuits up to 32 amps have a disconnection time of 0.4 seconds ,above 32 amps is 5 seconds , and again if you have a 17th addition board installed as IQ has stated there is no need for a 100ma RCD

its 1 s if TT

 

[mart8235]

It was the highlighted text in post 6, the word you used was 'must'-check it out.

I just don't want anyone reading the thread to assume that the 100mA front end rcd is the in stone TT setup.

The introduction of BS7671:2008 virtually eliminated the need for the above scenario.

I put '17th edition' consumer unit in inverted comma's to show that the terminology was incorrect but to save describing it's setup.

No more shout typing so don't disturb your mum

Well..... yup.... it seems I did say 'must'. don't know what that was all about, I know better than that!
I'm only yanking ya chain about the board, but you knew that!
can I amend the post? I'll try now........


..........Yup changed now

 

[morph]

COULD BE 100, 300 rcd depends on ZE

 

[IQ Electrical]

COULD BE 100, 300 rcd depends on ZE

You're missing the point!

 

[Deleted member 26818]

Yes, it depends on Zs.