Type B Fuse keeps popping

[hohingday]

Hi All,

I was hoping to get some advise, I have an old consumer unit with a Type B Breaker that has popped 3-4 times over the last couple of months.

I cant seem to isolate where it is coming from as it happens quite erratically and it would be unpractical to leave the sockets unused for weeks to test them.

Yesterday morning when it popped I was not able to turn it back on straight away despite unplugging all devices it kept popping. However when I returned in the evening I was able to turn it back on.

I have replugged everything in and all seems to be working but obviously this is worrying, any ideas what would be causing this?

Also how difficult is it for an Electrician to isolate a fault like this? I am keen to get someone in but I am wary of getting stuck with a bill for hours and hours of unsuccessful detective work.

Thanks

 

[endecotp]

What is connected to the circuit?

 

[ban-all-sheds]

What's the rating of the MCB?

 

[hohingday]

Its 16Amps and the following are connected - Tv, Amp, 2 PCs, 2 Routers, Couple of Phone and Laptop Chargers.
Thanks.

 

[ban-all-sheds]

For a B16 breaker to trip, there has to be a fault of at least 23.2A flowing. And then that would take an hour. For it to trip "instantly" you're looking at 80A or more.

That's 5.3kW and 18.4kW of heating respectively.

If it's tripping with nothing plugged in then somewhere in that circuit you have got that much heating going on where the fault is.

You should get an electrician before you need to get a fireman.

 

[hohingday]

Ok sure I will look one up.
I know this is an open question, but any ideas what something like this would cost to remedy? Would you pay per hour?

 

[bernardgreen]

Definately get an electrician BUT do not expect an instant solution / diagnosis.

In view of the potential fire risk switch the breaker of when sockets are not being used.

One possibility is that a cable is trapped under a floor board and when someone puts their weight on that board the cable is crushed and the conductors short out. That trips the breaker.

Unless someone happens to walk on that board when the electrician is testing the circuit the fault will not be found by simple testing.

 

[hohingday]

Thanks for the responses, I will try find someone, if anyone is available to help over in the Erith area then please do get in touch...

 

[JohnW2]

No-one seems to have yet mentioned the possibility that it could just be the breaker itself which has become faulty and is occasionally tripping spontaneously when it shouldn't. Unfortunately, that can't really be diagnosed other than by excluding all other possible causes (and, since even they would presumably be intermittent, even that could be a nightmare).

I would also add that although everyone is probably right in assuming that the 'breaker' is an MCB, I don't think we're actually certain that it's not an RCBO - which, of course, would change things a bit. hohingday: does the breaker have a test button on it?

Kind Regards, John

 

[hohingday]

Hi John, the breaker is a MCB, no test button, I don't think it is actually the breaker as when it first happened I replaced the old plug in fuse with the MCB, unless I got really unlucky?

 

[endecotp]

Is there any RCD protection?

 

[hohingday]

No its one of those old metal type CUs.

 

[Taylortwocities]

So that does sound like a short circuit, somewhere. It takes more current to blow a fuse than an MCB and the fault pops both, so that eliminates the MCB being faulty.
Definately time to get someone in for investigation.

Save some time (and money) before he/she comes by going round the house and detailing EXACTLY what sockets (and other items) are powered on that circuit.

EDIT: a list of registered electricians can be found here
http://www.electricalcompetentperson.co.uk

Note that the term "competent" does not necessarily mean capable! Your best bet is using someone who comes from personal recommendation.

 

[JohnW2]

Hi John, the breaker is a MCB, no test button, I don't think it is actually the breaker as when it first happened I replaced the old plug in fuse with the MCB, unless I got really unlucky?

Thanks. I take it that you mean that you experienced occasional (and unexplained) fuse blowing before changing to an MCB? If so, as TTC says, that does sound like an intermittent short circuit. That would presumably have to be in the fixed wiring of the circuit (including connections to sockets) or conceivably within the plugs - the only loads you have mentioned are small electronic ones, and I don't think that any of them are likely to result in a current high enough to blow a 15/16A fuse/MCB without themselves blowing up - or, at least, dying.

I'm sure we don't need to tell you that getting to the bottom of intermittent faults can be a very difficult process! Do I take it prior to the last few months (or however long), this circuit had been working fine for some time, without any fuses blowing etc.? If so, had any work (flooring, plumbing etc.) been done around the time that the problem first arose? Are you aware of any problems with rodents (rats/mice) in the house?

Kind Regards, John

 

[hohingday]

Yes that is what I meant, it blew twice so I replaced it with a MCB. I have lived here for around 18months and it never happened prior to the first time circa 3 months ago.

There hasn't been any rodents or major work around the house.

Thinking back when it has blown, there seemed to a popping noise coming from around a blanking plate, does this suggest anything?