MCB trips too quickly

[opps]

Hi all

My friend's kitchen and extension lights have a "master" on/off switch. The switch controls all of the ceiling lights, wall lights and kitchen cabinet lights. Each set has its own dimmer switch and each night he just flicks the master switch to turn them off. In the morning he flicks the master switch to turn them back on. Doing so trips the lighting MCB.

I did recommend manually turning off some of the lights at night so that there will be less initial draw in the morning. Doing so doesn't trip the MCB.

The lights are all LED. I guess the initial draw is too great for the MCB. Can you get MCBs that take slightly longer to trip?

Thanks.

 

[JohnD]

you can, I used them when fitting new stage lighting once to replace old fuseboards, and they are used on motors and other things with high start-up loads. X-ray machines used to have the worst.

But there is a calculation to be done, which I can't remember

This was in the old days of filament bulbs. The load on modern LEDs is so tiny I didn't think you'd get it on a domestic circuit.

Do you know what sort of bulbs he has? Halogen spotlights and transformers are way out of date now.

How old is the MCB? Is it a B6?

Edit:
come to think of it, C and D types are not common domestically, so most brands may not be available to fit a house CU anyway.

 

[blup]

Unless he has hundreds of downlighters, the wattage of the LED's even on a 1mm cable served by a 6 amp breaker shouldn't trip the MCB, so more likely to be the wiring of the accessories/circuit, or a faulty dimmers.

Can you confirm the number of lights, and the size of the circuit cable and rating of the breaker?

Blup

 

[Swwils]

It might not be a MCB; is it a RCBO?

 

[opps]

you can, I used them when fitting new stage lighting once to replace old fuseboards, and they are used on motors and other things with high start-up loads. X-ray machines used to have the worst.

But there is a calculation to be done, which I can't remember

This was in the old days of filament bulbs. The load on modern LEDs is so tiny I didn't think you'd get it on a domestic circuit.

Do you know what sort of bulbs he has? Halogen spotlights and transformers are way out of date now.

How old is the MCB? Is it a B6?

Edit:
come to think of it, C and D types are not common domestically, so most brands may not be available to fit a house CU anyway.

I will get him to count the number of lights. Thanks.

 

[AndyPRK]

Should be able to get C6 for domestic.
What brand is his CU.

 

[opps]

Unless he has hundreds of downlighters, the wattage of the LED's even on a 1mm cable served by a 6 amp breaker shouldn't trip the MCB, so more likely to be the wiring of the accessories/circuit, or a faulty dimmers.

Can you confirm the number of lights, and the size of the circuit cable and rating of the breaker?

Blup

Thanks, will post back once I have the info.

 

[opps]

It might not be a MCB; is it a RCBO?

I shall check. Thanks

 

[opps]

Should be able to get C6 for domestic.
What brand is his CU.

Thanks Andy. I will find out.

 

[JohnW2]

Should be able to get C6 for domestic.

Indeed, but it really shouldn't be necessary fo just a pile of LEDs - even if it is a fairly large pile. I think there's is more to this story than the 'start-up current' of a number of LEDs tripping a (normally functioning) B6.

Kind Regards, John

 

[JohnD]

it might be the dimmers doing it.

 

[333rocky333]

What drivers is he using, many have inrush currents

 

[Aragorn84]

Or LED power supplies with a bunch of caps in them, perhaps of dubious quality, all sapping a chunk of power at once....

 

[JohnW2]

it might be the dimmers doing it.

What drivers is he using, many have inrush currents

Or LED power supplies with a bunch of caps in them, perhaps of dubious quality, all sapping a chunk of power at once....

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

 

[ericmark]

With LED bulbs in the main current limiting capacitor then rectifier then smoothing capacitor, so unlikely to cause tripping, would seem more likely @333rocky333 is closer and using some sort of power supply which drops voltage, but type B is between 3 and 5 times running current so B6 needs 18 amp to trip, that seems rather high for LED.

I would agree with @JohnW2 I think some thing missing in the story.