Main 'fuse' (RCD) tripping

[barki]

Hi all,

I have a consumer unit in the house but the main fuse is next to the meter which is installed on the wall in the garage.

I realise that individual circuit fuses tripping normally indicates a fault on that circuit.

However, my main fuse (not the one on the consumer unit but the one on the main incoming cable next to the meter) has just tripped for the second time this week.

Never ever had to reset one of those before, I wasn't concerned when it happened the first time, but now I'm wondering.

Any thoughts on whether or not I need to call an electrician? I'm capable of basic legal DIY electrical work, but I don't fancy touching the main fuse (or the consumer unit).

P.S - This may not be related but as it happens my area has had loads of power cuts recently. Like 8 or 9 within the last month. At first I figured it was just another powercut and I my checked my own fuses when I saw the the neighbours had power some 6 hours later. Might the powercuts have damaged the main fuse?

Cheers for any help

 

[EFLImpudence]

To be certain, can we please have a picture of the fuse in question?

Just copy and paste the picture.

 

[barki]

Yep, as attached.

 

[opps]

It looks like a RCD.

 

[EFLImpudence]

Yes. That means it trips because of current leakage to earth (not returning through the Neutral) so the fault could be anywhere and you probably will need an electrician.

Having said that, some times they do just trip so the power cuts might be doing something although surely the timing would indicate if that was the case.

 

[JohnD]

It is not a fuse. It is a residual current circuit breaker. It trips when there is a leakage of electricity to earth, for example due to a water leak in a kettle, or a split heating element in a washing machine or oven, or rain getting into an outdoor light, or a person touching a live or damaged wire, or a dog chewing a flex.

(By far the most common trips are water related)

I have also known RCDs trip when a timeswitch cuts in or out. You can sometimes track down the cause by logging the time and day, and what appliances were on.

Yours is 100mA, which is quite low sensitivity, and would not stop you getting a painful jolt, though it would reduce the chances of you dying from it. These are sometimes used where the house has a poor earth connection, sometimes in old houses or rural areas with overhead supplies. The electricity company may be able to provide a better earth.

These were formerly used to give a degree of protection in homes, but there are now smaller and better ways of adding protection.

 

[barki]

Ok thanks all.

I admit am surprised because previously what you describe would always have tripped one of my smaller circuits on the consumer unit, never this big one before.

 

[AndyPRK]

Pic of your consumer unit please ?

 

[JohnD]

Ok thanks all.

I admit am surprised because previously what you describe would always have tripped one of my smaller circuits on the consumer unit, never this big one before.

The "smaller" circuits trip when there is an overload or short putting the current sufficiently above the rated value (for example if you tried to supply a 13Amp kettle from a 6A lighting circuit).

The RCD works differently.

It knows that electricity in a circuit should flow up* the live wire and back down* the neutral wire, so the two currents should be the same.

If, instead, you touch the live wire with your finger while holding the kitchen tap, some of the current will flow through your body to earth, causing your heart to stop and other inconveniences.

The RCD is capable of detecting that the current through the L and N no longer match, and cutting the power in a fraction of a second. It can detect very small differences in current.

*not quite true, but near enough

 

[barki]

Pic of your consumer unit please ?

 

[JohnD]

That's very odd.

The big RCD looks quite modern. Who fitted it, and why?

Do you have other supplies, for example to an outbuilding?

Please stand back and take a wider pic, showing the incomer, meter, consumer units and switches and the cables around and between them.

What does the B40 circuit do?

 

[AndyPRK]

What does the b40 do by red switch

 

[ericmark]

As said doing my maths, 30 mA + 30 mA = 60 mA and the independent one is 100 mA so it should not trip unless the fault is due to the odd MCB out so one wonders what it does?

 

[Scally-Ho]

Before this topic progresses any further, do you have an overhead mains supply feeding into your house?

 

[barki]

Hi all.

Thanks v much. Answers to questions as follows:


- The B40, sadly I do not know what that does. No instructions. I didn't live here when it was fitted. Looks like next I selection is due on a 5 year cycle in December this year. I moved here in 2021.

- Outbuildings, yes there is a other smaller consumer unit in the garage. I didn't mention initially (the plot thickens) as I felt it would have the same relationship to this main RCD that's been tripping as the main consumer unit does, which is in the kitchen.

Photo now attached on the meter arrangement in the garage as well as the smaller consumer u it next to it. In holding the panel infront of the electricians contact details deliberately (never met him, but I feel it's just the right thing to do especially is someone on here isn't impressed with what they see).