Nuisance Tripping

[monday]

I have a problem with nuisance tripping of MCBs when a light bulb blows. The house was built 1996/7 with a Hager split load CU. Electrics basically original although a new sub CU was installed 4 years ago to cater for a new kitchen with some re-arrangement of circuits such that downstairs lights are on the RCD side of the original CU and upstairs lights on the non-RCD side.

However tripping has been an issue since the house was new, since the CU is outside in the (integrated) garage. It is a reducing problem as we have less tungsten filament bulbs now but still a nuisance when a trip occurrs late at night.

I get the impression that RCBO's might fix this but can I just use them on lighting circuits and will they fit?

Any advice gratefully received.

 

[PrenticeBoyofDerry]

I get the impression that RCBO's might fix this but can I just use them on lighting circuits and will they fit?

Why would you expect an RCBO to deal any better with a circuit thats overcurrent protection device is tripping when the lamp blows, what type/make of lamps are you using?

 

[ericmark]

In theroy all tungsten bulbs should have a built in fuse so if when they blow one gets ionisation inside the bulb it will rupture the fuse rather than take out the trip.

However this is theroy in practice often not fitted as few bulbs now made in UK most come from China.

Also the problem is a trip (MCB) is a two part device thermal and magnetic. So with a B6 after a long overload above 6A the thermal part will trip but it will take a long time. The B in the B6 means 5 times so within 0.01 of a second the magnet part will open the trip at 30A.

Often the RCBO is not a B6 but a C6 so the magnetic part is rated at 60A so more likely the internal fuse in the bulb would open first (if it exists). However just swapping to a C6 MCB would do the same thing.

However there are some dangers in changing to C (x10) or D (x20) rated MCB. One is the loop impedance of the circuit which should be tested before the change and the other far more important is with the C or D rated trips there is a chance when a bulb blows it will melt the solder on the connections and weld the bulb into the holder so instead of changing a bulb you have to swap holder as well.

CFL and LED can still take the trip out when they go but since they last longer it does not happen as much and to me swapping bulbs every week is a pain so nothing to do with saving energy I swapped first to CFL and am now moving to LED and the B6 trip in my garage has not tripped in years since tungsten lamps were replaced.

 

[monday]

I get the impression that RCBO's might fix this but can I just use them on lighting circuits and will they fit?

Why would you expect an RCBO to deal any better with a circuit thats overcurrent protection device is tripping when the lamp blows, what type/make of lamps are you using?

Only what I read somewhere here, hence the question. But I think Ericmark has answered it.

Bulbs are any kind of tungsten bulb, consistently since the house was new. Possibly LED's as well but as Eric says, those and CFLs blow much less often.

So no real solution?

 

[AndyPRK]

The solution is to fit a Type C device to the lighting circuits which annoy you.

e.g C6.

This could be an MCB or RCBO.

post a picture of your consumer unit.

 

[monday]

The solution is to fit a Type C device to the lighting circuits which annoy you.

e.g C6.

This could be an MCB or RCBO.

post a picture of your consumer unit.

Thanks AndyPRK but Ericmark he say potentially bad for bulbholder?

It's a standard Hager CU with 6xMCB's on the RCD side and 5xMCB's on the non-RCD side.

 

[PrenticeBoyofDerry]

You would also need to confirm you have a suitable loop impedance.

 

[EFLImpudence]

Eric's 0.01 should be 0.1 second.