Circuit breaker for lights is broken/faulty

[mdsimpson]

Hi,

Newbie looking for some advice, not sure if I am using the right terminology so please bare with me.

The circuit breaker controlling our lights appears to be broken but I want to check my rationale before I get an electrician out to help.

The circuit has flipped to the off position a number of times over the last couple of days but no lights have blown as a result, though they do all switch off. It doesn't appear to matter what lights are on. When I have checked the circuit breaker and flipped it back up the lights come on and so I have not done anything else about it. This last time the breaker has been warm but also doesn't provide power to the lights unless I keep the switch pushed up. Otherwise it stay in the on position but the lights do not work.

I think it is faulty/broken and needs replacing and from what I can see they are about £5. Is it possible for a complete novice to replace or should I stay well clear?

Thanks

Mark

 

[Adam_151]

That does sound unusual

What make is the consumer unit, and when was it fitted?, there was a recall on some makes a few years back

Although its equally possible the outgoing live is just loose, or even the busbar cage terminal is the wrong side of the copper stab

Generally not a task for a DIYer as it involves working in an enclosure with live parts and there is going to have to be some investigation as to the exact nature of the fault

 

[ericmark]

The trip is a duel unit in one both thermal and magnetic and under load it will become warm this is how it works.

The question is has the trip opened because there is a fault on the circuit and it's doing it's job or because the trip its self is faulty?

You should not be able to force a trip into the on position if it's faulty but it may have become faulty because it was overloaded in the first place so step one is count up and add the wattage of your lights and see if this is anywhere near the point where it should trip.

4A = 920W, 5A = 1150W and 6A = 1380W and any florescent lamps can use up to 20% more than the rating on the tube.

It is very easy to hit the limits when spot lights are used. Also lamps can go faulty and draw more than they are rated at but if I look at my own house you will see how it can all add up.

Kitchen 2 x 60W florescent so extra 20% = 144W.
Dinning room 6 x 60W tungsten = 360W
Living room 10 x 60W = 600W
Landing 1 x 18W florescent HF type so 18W
3 Bedrooms with 60W = 180W
Bedside lamps 2 x 50W spots one 60W angle and a 22W 2D = 182W
Office 20W strip light and 60W bulb = 80W
Total = 1564W which will open the trip. Cure was to swap some of the lamps.
Dinning room 6 x 8W CFL
Living room 2 x 1.6W LED and 8 x 3W LED
Bedrooms 22W CFL
Spots swapped to 2W LED GU10 units
Also started switching off lights result no longer overloaded.

So if you do a similar sum for your house and see your house fairs. Because we have ceiling roses and other items which are rated at 6A in the main we are stuck with a 6A MCB. There was a move to split the circuits up and down stairs but in many houses this means the two way lighting has to be disconnected because of borrowed neutrals and when upgrading to RCD protection it becomes very apparent when there is a borrowed neutral and where split it has to be combined again or two way switching disabled.

If the count is OK and not overloaded then next step is a clamp on ammeter to see if some item is faulty and drawing more than it should. Changing a MCB will likely remove the problem for a time as they will hold for quite a time on a slight overload but as time goes one when overloaded on a regular basis they get weaker and weaker so just swapping is not the answer.

 

[mdsimpson]

Thank you for your replies.

Having done some for investigation it would appear that the MCB in question is included within the product recall from 09/10. It is a NSB06 and there is some browning on the side of the MCB where it has overheated.

I have tried Electrium's products recall number but it would appear they are off for the holidays. Does anyone know whether I can get an electrician out and make a subsequent claim?

I will get the electrician to check the overall load on the lighting as we'll to see whether this was a factor thank you ericmark.