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]

If the 30ma device is for additional protection bottom line is you need both the x5 tests to be less than 40ms, record the highest of the two x5 readings. (EDIT if you only have space for one reading)
The two x0.5 tests (no trip) and two x1 tests ( < 300ms ) still need checking of course.

 

[Rockingit]

You're recording the characeristics of the RCD element of the device, nothing else, so you're recording both. And if your times are <300mS on 1x and <40mS on 5x then you're all good. One thing that's changing is that the newer type A / B / F RCD's tend to have longer times than the AC types we're all used to, but perfectly acceptable.

 

[Razzle12]

If the 30ma device is for additional protection bottom line is you need both the x5 tests to be less than 40ms, record the highest of the two x5 readings. (EDIT if you only have space for one reading)
The two x0.5 tests (no trip) and two x1 tests ( < 300ms ) still need checking of course.

Hi Tim
Cheers for that ,but the device is a combined RCD/afd and is designed for fault protection,and not additional protection,so guess it's the highest x1 value of both sides of the wave .

 

[snowhead]

Is it;
RCBO / AFDD or
RCD / AFDD ?

 

[Razzle12]

You're recording the characeristics of the RCD element of the device, nothing else, so you're recording both. And if your times are <300mS on 1x and <40mS on 5x then you're all good. One thing that's changing is that the newer type A / B / F RCD's tend to have longer times than the AC types we're all used to, but perfectly acceptable.

Hi tim
Thank you very much ,is there a reg No that determines those values please .
Regards

 

[Razzle12]

Is it;
RCBO / AFDD or
RCD / AFDD ?

Hi they are RCD/AFD devices

 

[Rockingit]

The pedant in me needs to point out that the device is the device (in this case a combined RCBO & AFD) - it has no say in how it gets deployed and doesn’t know what level of protection it’s been put into circuit for. Ergo, you test it the same as any other device - RCD times and compliance (on the circuit) for ADS times.

 

[UNG]

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

What test current are you applying for the 5x test as some of the newer breakers are designed to operate at a higher trip current of 250ma and not the usual 150ma

 

[Razzle12]

What test current are you applying for the 5x test as some of the newer breakers are designed to operate at a higher trip current of 250ma and not the usual 150ma

30mA trip test current
Regards

 

[timhoward]

I'm actually a bit confused what the actual question is and if it's been answered! ;-)
When you say it's for fault protection are you referring to the AFDD part of it, or meaning it's installed to provide ADS for an installation, e.g. a main switch or up front device on a TT system?

,is there a reg No that determines those values please .

The time/current criteria is in Appendix 3 of 18th, page 363
Also see reg 643.8, note underneath.
However if it is for fault protection and providing ADS for an installation then chapter 41 applies.
If we can help more then feel free to tell us a bit more about how/where this thing is installed, and what you are unsure of. ;-)

 

[Razzle12]

I'm actually a bit confused what the actual question is and if it's been answered! ;-)
When you say it's for fault protection are you referring to the AFDD part of it, or meaning it's installed to provide ADS for an installation, e.g. a main switch or up front device on a TT system?



The time/current criteria is in Appendix 3 of 18th, page 363
Also see reg 643.8, note underneath.
However if it is for fault protection and providing ADS for an installation then chapter 41 applies.
If we can help more then feel free to tell us a bit more about how/where this thing is installed, and what you are unsure of. ;-)

Hi Tim
I'm working on a youth hostel ,and this is a brand new install ,this relates to one of two three phase boards ,of which almost every single phase breaker is a combined RCD/AFD device ,just would like to know the maximum Ms for the x1 test at 30mA.
Regards

 

[timhoward]

Wow, sounds like someone was flush with cash! Do you have a photo?!

Anyway, posts 2 and 3 are correct, irrespective of the fact they are combined devices, maximum 300ms at 30ma (x1), maximum 40ms at 150ma (x5).

The x5 time still needs to be complied with and if you only have one box to write a result (like the latest NAPIT model form) you'd write down the biggest x5 value.

(The only extra complexity is if the earthing is TT then the x1 would need to be under 200ms)
Hope that helps.

 

[Razzle12]

Wow, sounds like someone was flush with cash! Do you have a photo?!

Anyway, posts 2 and 3 are correct, irrespective of the fact they are combined devices, maximum 300ms at 30ma (x1), maximum 40ms at 150ma (x5).

The x5 time still needs to be complied with and if you only have one box to write a result (like the latest NAPIT model form) you'd write down the biggest x5 value.

(The only extra complexity is if the earthing is TT then the x1 would need to be under 200ms)
Hope that helps.

Hi Tim
Thanks so much for that ,and it's a TNS SYSTEM ,and the device is for fault protection and not additional protection so it should be the highest result on the x1 setting at 30 mA
Many thanks
Can send pic tomorrow if you want ,and yes guess the boards and breakers are expensive ,and was designed by Siemens.
Regards
Ray

 

[Julie.]

I am struggling to understand this.

You have a cu, (std switch on incoming) and each outgoing circuit has a combined rcd/afdd - is this correct?

If so where is the overcurrent protection for each circuit (fault and where needed overload)?