MCB trips too quickly

[Aragorn84]

All theoretical possibilities, but it sounds as if we are talking about 'immediate' (presumably magnetic) tripping of the MCB (if that's what it is) - so potentially in the ballpark of 30A for a B6.

Given that we are talking about dimmers, drivers/PSUs and LEDs which are all working satisfactorily (when working), hence no 'blown up capacitors' or other faults etc., it's almost beyond belief that inrush current (to charge capacitors or whatever) for even a large number of dimmers/PSUs/LEDs could be remotely near the level that could trip a normally-functioning MCB.

[in passing, as for capacitors "perhaps of dubious quality", I would expect the 'dubious quality' to result, if anything, in lower 'start-up/inrush' currents, whether due to capacitance being less than it 'said on the tin' or by have high internal resistance ]

Kind Regards, John

Perhaps. I know in our office we had issues with the B32 breakers in the main office and a bunch of PC's. If the power ever went off, the inrush of ~30 PC's would trip the breakers every time. Swapping the B's out for C's fixed it.

Cheap supplies might well be missing the inrush limiting components such as NTC's.

 

[bernardgreen]

I have seen a few LED drivers integrated into lamps where the mains supply goes via a low ohm resistor to the bridge rectifier and the DC then to a capacitor. Inrush current was high.

Where a lot of equipment being switched at the same time and inrush current is causing MCB to trip one solution is to stagger the total load using a chain of slow acting relays ( or contactors ) to sequence the power up of the many bits of equipment.

 

[Aragorn84]

Where a lot of equipment being switched at the same time and inrush current is causing MCB to trip one solution is to stagger the total load using a chain of slow acting relays ( or contactors ) to sequence the power up of the many bits of equipment.

Interesting. I picked up a rack mountable IEC C13 PDU to mount behind my AV cabinet at home to supply power to all the various kits of kit in the cabinet. I noticed it was banked in three sets of four, and has some sort of timed relay setup where it brings each bank in a second after the preceding one. I did wonder what the point of that was, as its not manually controllable in any way, i've seen fancier ones before where you've got full remote control over the ports via serial or ethernet, or can manually switch the banks in and out, but this one is just on a fixed timer. But you've nailed it there, it'll be to ensure powerup happens smoothly and doesnt trip breakers.

 

[JohnW2]

Perhaps. I know in our office we had issues with the B32 breakers in the main office and a bunch of PC's. If the power ever went off, the inrush of ~30 PC's would trip the breakers every time. Swapping the B's out for C's fixed it.

Fair enough, but I think we are talking somewhat of 'chalk and cheese' here.

Depending on their age and size, the total normal running current of ~30 PCs could come not all that far short of 'fully loading' a 32A circuit, so any amount of inrush current could start moving the transient total towards the trip threshold.

On the other hand, the normal running current of even a large handful of LEDs (and associated components) would be tiny in comparison with the In of even a B6.

Cheap supplies might well be missing the inrush limiting components such as NTC's.

Yes, one can postulate all sorts of possible mechanisms - but I still 'find it hard to believe' that the total inrush of a handfull of LEDs would, in the absence of 'faults'(which I suppose might be 'design faults') be enough to trip any MCB. However, maybe I'm wrong in that belief!

Kind Regards, John

 

[opps]

Hi all

Here is a (not very good) panoramic photo of the room.




There are a total of 45 LED bulbs. The recessed ceiling lights are GU10 LEDs, there are three LED pendant filament lights and the rest are low profile circular LEDs under the kitchen wall units and then LED downlighters in the two skylights.

This is the light switch grid



And here is the MCB- the consumer unit is MK but the MCB (10 amps) is a Hager MTN110



The above is the right hand side of the consumer unit. Incidentally, there is no blank plate to the left hand side of the rcd (ie there is a void) and all of the MCBs seem to be slanted...

Hope the photos help, thanks once again.