Fusebox RCBO trip / ramp

[Timotei]

Fitting a new CU today (domestic TT) and using "Fusebox" for the first time - 14 way Type A RCBO board, 9 ways used 5 spare.

All good until testing RCBO trip times - 7 test perfect, but 2 (both 6A) tripping during half test, 1 @ 0 the other @ 180. All loads disconnected, tested again, same results. I'm assuming these 2 are faulty or have I missed something at the end of a long day?

Ramp test for all 9 RCBOs trips @ 18mA. To my mind this is much too low, but I assume this is the design as they are all the same. (MFT recently calibrated and working fine as far as I'm aware from other tests and recent use.)

Anyone else had any issues with these RCBOs / the brand?

I have another 6 way RCBO board to fit this weekend so a little anxious...

Timotei

 

[buzzlightyear]

what did you get for the lights ?

 

[Baddegg]

Fitted 4 of these now with no probs at all so far......could be faulty batch, do you have any more 6a to try?

 

[Lucien Nunes]

Did you test with the outgoing circuit connected for both ramp and normal test sequence? 18mA is unusually sensitive but in spec. However 3mA of leakage from the system plus 15mA from the tester will trip it.

 

[Wilko]

Hi - the rcbo shouldn’t trip at 15mA or less, so the 18mA a pass for the ramp test. Why these are tripping during the 1/2 test I don’t know. The MFT usually apply 15mA for 2 seconds to confirm compliance to this part, so from your ramp test your rcbo should have been ok... Possibly your tester applies a little more than 15mA(?). Do you have access to another tester to perhaps confirm the result?

 

[buzzlightyear]

try and test at the board and see what results you are getting .

 

[westward10]

He states loads are disconnected and gets the same result.

 

[Timotei]

what did you get for the lights ?

dont have the exact results to hand, but all comfortably within expected parameters, IR / ZS etc, I'll try to dig out the actual figures later

Fitted 4 of these now with no probs at all so far......could be faulty batch, do you have any more 6a to try?

One 6A on the board testing fine, have 2 more for the weekend's board....hoping they'll be ok

Did you test with the outgoing circuit connected for both ramp and normal test sequence? 18mA is unusually sensitive but in spec. However 3mA of leakage from the system plus 15mA from the tester will trip it.

Tested with the L / N disconnected completely, so just the RCBO and still trips on half test

Hi - the rcbo shouldn’t trip at 15mA or less, so the 18mA a pass for the ramp test. Why these are tripping during the 1/2 test I don’t know. The MFT usually apply 15mA for 2 seconds to confirm compliance to this part, so from your ramp test your rcbo should have been ok... Possibly your tester applies a little more than 15mA(?). Do you have access to another tester to perhaps confirm the result?

I don't currently have another tester to confirm, but will try mine on an RCBO at home later and see what results I get

 

[Julie.]

Are you testing the correct type?

Mft set for a, actual rcbo ac etc.

 

[NDG Elecs]

I would say they are cheap for a reason. That being the manufacturing processes are not as good as they perhaps could be. Pay peanuts springs to mind. I stopped using BG for this very reason - too many icky RCD results.
18mA is on the low side but given it is 18mA per circuit then that should not be an issue..

 

[Timotei]

Are you testing the correct type?

Mft set for a, actual rcbo ac etc.

Hi Julie, yep, checked time and time again! Started early morning (lots of floods here in Shrewsbury, if you don't get underway before dawn it takes hours to travel even a short distance at the moment!) so wondered if I was making a simple mistake due to fatigue, but all as it should be...I think I have to accept that 2 of the 9 are faulty....not a good first impression!

I would say they are cheap for a reason. That being the manufacturing processes are not as good as they perhaps could be. Pay peanuts springs to mind. I stopped using BG for this very reason - too many icky RCD results.
18mA is on the low side but given it is 18mA per circuit then that should not be an issue..

They are cheap in comparison to many / most brands, but have excellent reviews and are highly recommended by many people,....haven't seen anyone else suggesting any faults until now so just wondered....I still think 18A is too low even for single circuits....have 2 more arriving tomorrow, if these don't test perfectly will not be using again...

 

[NDG Elecs]

Hi Julie, yep, checked time and time again! Started early morning (lots of floods here in Shrewsbury, if you don't get underway before dawn it takes hours to travel even a short distance at the moment!) so wondered if I was making a simple mistake due to fatigue, but all as it should be...I think I have to accept that 2 of the 9 are faulty....not a good first impression!




They are cheap in comparison to many / most brands, but have excellent reviews and are highly recommended by many people,....haven't seen anyone else suggesting any faults until now so just wondered....I still think 18A is too low even for single circuits....have 2 more arriving tomorrow, if these don't test perfectly will not be using again...

Yep, to be fair many have sung their praises. I hope you report back if there are any issues with the next couple of one's.

 

[Risteard]

18mA complies with the requirements. I don't really see the point of ramp testing for verification given that the standard tests already prove it is operating correctly.

 

[westward10]

There is no specified value at which a 30ma rcd/rcbo must trip, aside from that between 50% and 100% of its rated operating current it should trip. Manufacturers never manufacture a device to trip at 100% of this operating current due to unknown factors, as such for a 30ma device it is manufactured to operate at 27 - 28ma (93 - 94% of its operating current). I agree that 18ma is low but nevertheless it falls within specifications.

 

[Timotei]

18mA complies with the requirements. I don't really see the point of ramp testing for verification given that the standard tests already prove it is operating correctly.

There is no specified value at which a 30ma rcd/rcbo must trip, aside from that between 50% and 100% of its rated operating current it should trip. Manufacturers never manufacture a device to trip at 100% of this operating current due to unknown factors, as such for a 30ma device it is manufactured to operate at 27 - 28ma. I agree that 18ma is low but nevertheless it falls within specifications.

Thanks both, my issue is that both these 6A RCBOs trip during the half test, so do not comply with the requirements / are not operating correctly as you suggest Risteard.

I always ramp test, as much for my own interest as anything else, but also in the hope of avoiding call backs in the future. I apologise if my ramp test query has distracted from the main point that 2 of the 9 RCBOs do not test correctly.