Blowing bulbs and MCB's

[Richard_Baxter]

I have 4 separate lighting circuits on my CU (MCB's in non RCD side of split CU) and every time a tungsten filament or mains halogen goes it instantaneously trips the relevant MCB everytime without exception. I have changed a few bulbs for 20x CFL, but these haven't blown yet so not sure what will happen when they do. (BTW bulbs don't blow frequently - they last their stated hours)

MCB's are 6amp type B.

I know that starting currents are quite high for a split second until filament has heated up and this is why bulbs blow when turning on lights (usually), but for a MCB to trip this must really be some overcurrent to 'instantaneously' trip the MCB.

I ask this as I was last night plunged into darkness during a nappy change at great inconvenience (this was my baby's nappy, not mine!!)

Can anything be done stop this happening and circuits being so sensitive?

 

[Spark123]

A type B MCB will open at 3-5 x its rated current within 0.1s. This means as little as 18A is required for a short duration to trip a 6A MCB.
Using CFLs is as good a solution as any, they don't fail the same way as a filament lamp does.

 

[JohnD]

IMO CFLs are the best solution. there are other ways but they are more costly and require professional work.

Some people say that better-quality light bubs don't have this problem. Osram is often mentioned.

In my house, the kitchen spots trip the MCB every time; nothing else does. It might be relevant that the circuit length to the kitchen is much shorter than the other circuits.

 

[ban-all-sheds]

Some people say that better-quality light bubs don't have this problem. Osram is often mentioned.

Dunno about Osram, but I've tried other quality lamps with built-in Ballotini fuses and IME it makes b****r all difference.

3 non-CFL solutions (some of which require a bit of investigative work on the circuits first):

1) replace the B6 with a C6.

2) replace the B6 with a B10.

3) replace the B6 with a B20 or 25 with 2.5mm² cable from there to an FCU next to the CU with a 5A fuse in it, and the existing lighting circuit supplied from that.

 

[Steve]

3 non-CFL solutions (some of which require a bit of investigative work on the circuits first)

3 non-CFL solutions (ALL of which require a bit of investigative work on the circuits first)