6amp RCBO or Mcb that doesn't trip everytime a bulb blows

Never really thought of it as an issue tbh but what about fitting a fuse carrier instead of an MCB and putting a 5A fuse in.

Leesparkykent said:

Never really thought of it as an issue tbh but what about fitting a fuse carrier instead of an MCB and putting a 5A fuse in.

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LOL. Until recently I had a BS 1361 cartridge fuse board in the house. Many times a failed lamp took out the 5A BS 1361! Since the banning of incandescent lamps other than rough service types it seemed to get much worse - with every single lamp failure taking out the fuse. (Believe it or not on one occasion a failed lamp caused the RCD to operate.)

You can't without changing the lamp from a filament to other type.

Basically what the OCPD see's is a short circuit and to get around this would mean you remove the protection that is required, when a filament lamp blows it sometimes creates an Ionized path where the filament used to be and this effectively is a short circuit until the arc collapses, the smaller and more compact the filament arrangement the more likelyhood of this occuring.

CFL, LED, Flourescents are not prone to this so the issue is removed but getting a elderly couple who swear blind that filaments are the only light they are comfortable with is a whole different problem.

You suggestion of changing the mcb curve or uprating to a 10 will not have much effect, again it's a short circuit so your not trying to combat inrush here but a very large current, the only thing that may reduce the problem would be to fit dimmers with a turn down to off position not the push to operate type, this way the lamps are gradually taken to full voltage and less likely to create the ionised path if they fail, a combination of thermal and magnetic shock are key parts of the shorting been created and if you dampen the shock you reduce the likelyhood of your issue occuring IMO. (I haven't tried this. I'm just using my knowledge of the problem itself)

Consider the shape of the bulb (yes I called it a bulb) for it's orientation, ie GLS should have the cap at the top, candle the cap at the bottom.
They were designed to be the shape they are, and it's not purely for cosmetic reasons.

We had a block where 3 corridors had about 8 fittings each, all with upside down candle bulbs. Due to the way it was laid out the rcd for the whole lot would go every time a bulb went. I changed them for LEDs to stop the problem, but I reckon using the correct bulb would have helped.

If you are changing the board I would ensure it is easily accessible for them, and make the labels really obvious (if that's possible!).

Incandescents/halogens are more likely to trip the MCB, so maybe change lamps to LEDs if they are happy to do so. I recently changed some GU10 halogens to LEDs in my elderly mother in laws and she had not noticed any strobing effect and is happy with them.

Adam W said:

Consider the shape of the bulb (yes I called it a bulb) for it's orientation, ie GLS should have the cap at the top, candle the cap at the bottom.
They were designed to be the shape they are, and it's not purely for cosmetic reasons.

We had a block where 3 corridors had about 8 fittings each, all with upside down candle bulbs. Due to the way it was laid out the rcd for the whole lot would go every time a bulb went. I changed them for LEDs to stop the problem, but I reckon using the correct bulb would have helped.

Click to expand...

I never thought about lamps having a correct orientation. Makes sense though.

Why are you considering changing the board?

Wouldn't fitting LED lamps be a better idea?

What about installing an emergency light fitting near the board?

I've had issues many years ago with dimmers getting damaged by lamps when their filaments blew. It was an interesting problem and I did a barrage of tests at the time to determine why so many dimmers were failing. It was one of those perfect storm type cases where the installation had an enormously high PFC (around 10KA) because the HV transformer was literally about 10 meters from the 200A 3-phase DB and the lighting circuits were also short and were on 4mm radials. They were losing a dimmer every week and had been as long as they had occupied the premises.

Our initial workaround was to install in-line fast-blow 3A fuses at each chandelier which effective even if it wasn't elegant, it meant that often when the lamp filaments blew they had to replace a fuse as well as the lamp. Eventually, in conjunction with the guys who manufactured the dimmer modules, I made up some small choke circuits that limited the fault current when the lamps blew to a level that didn't destroy the output diac.

Just out of interest I remember a time when filament lamps used to have a built-in fuse to prevent the fault current during filament failure causing the circuit fuse to blow.