UK RCD/ combined afdd breakers

[Razzle12]

Hi can someone tell me whether I need to record the trip times on x1 or x5 on this combined device,as I'm getting trip times of 44/45 ms x1 and sometimes a lot lower ie 29 ms.This device is the sole means of isolation.
Cheers

 

[timhoward]

Excuse particularly verbose answer, to try and clear up some confusion here.
Double pole RCBO's with AFD have three elements:
1) over current protection, same as fuse or MCB
2) arc-fault detection
3) RCD protection (earth leakage)

In BS7671 terms:
-fault protection is deemed to be via circuit's cpc, earthing, bonding and the fact that fault would operate the over-current element (same as fuse or normal MCB)
-the RCD element is providing additional protection.

The thing that seems to be causing confusion is that while the whole device is part of the circuit's fault protection, the RCD element is deemed to be additional protection.
I think most of the above is already understood and its just a terminology thing.

all I would like is the maximum mS parameters for x1 and X5 for the rcbo

x1 = 300ms
x5 = 40ms

 

[Julie.]

Excuse particularly verbose answer, to try and clear up some confusion here.
Double pole RCBO's with AFD have three elements:
1) over current protection, same as fuse or MCB
2) arc-fault detection
3) RCD protection (earth leakage)

In BS7671 terms:
-fault protection is deemed to be via circuit's cpc, earthing, bonding and the fact that fault would operate the over-current element (same as fuse or normal MCB)
-the RCD element is providing additional protection.

The thing that seems to be causing confusion is that while the whole device is part of the circuit's fault protection, the RCD element is deemed to be additional protection.
I think most of the above is already understood and its just a terminology thing.

x1 = 300ms
x5 = 40ms

Exactly!!!

Just because the combined device (rcd, mcb, & afdd) is the sole protection device, doesn't mean every aspect is the primary protection

The mcb aspect provides ADS.
The rcd aspect only provides additional protection in this case as ADS is provided by the mcb aspect.
The Afdd aspect is again additional protection although not under the same regulation as the rcd aspect.

This is important as when you complete the eicr or eic the rcd additional protection should be ticked and NOT the rcd as fault protection

This latter aspect should only be ticked/used if ADS cannot be provided without use of the rcd.

 

[Razzle12]

Excuse particularly verbose answer, to try and clear up some confusion here.
Double pole RCBO's with AFD have three elements:
1) over current protection, same as fuse or MCB
2) arc-fault detection
3) RCD protection (earth leakage)

In BS7671 terms:
-fault protection is deemed to be via circuit's cpc, earthing, bonding and the fact that fault would operate the over-current element (same as fuse or normal MCB)
-the RCD element is providing additional protection.

The thing that seems to be causing confusion is that while the whole device is part of the circuit's fault protection, the RCD element is deemed to be additional protection.
I think most of the above is already understood and its just a terminology thing.

x1 = 300ms
x5 = 40ms

Hi Tim
Thank you so much for this ,please can you tell me where these measurements are quoted in the regs book ,and as far as filling in the test sheets ,am I measuring on x1 or X5 .
Regards

 

[Julie.]

Hi Tim
Thank you so much for this ,please can you tell me where these measurements are quoted in the regs book ,and as far as filling in the test sheets ,am I measuring on x1 or X5 .
Regards

643.8

Or table 3A (only really applicable to fault protection as only the 40ms aspect is required for additional)

 

[timhoward]

Go on then, only because it's Friday....
Regulation 643.8 on page 235 describes testing RCD's, see note underneath for the 40ms.

The time/current criteria they need to come up to relevant standards is in Appendix 3, page 363

 

[Razzle12]

Go on then, only because it's Friday....
Regulation 643.8 on page 235 describes testing RCD's, see note underneath for the 40ms.

The time/current criteria they need to come up to relevant standards is in Appendix 3, page 363

Many thanks Tim .
Hopefully next time if I have to go on this forum ,I'll try and give as much info as poss.
Regards