RCD tripping - Weather-related?

RayM

I don't know much about electrics, so apologies if I use any incorrect terminology...

I woke up this morning to find that none of my sockets were working. I reset the main RCD switch and it immediately tripped again. So I unplugged everything in the house and tried again. Same thing happened. When I went through all the smaller circuit-breaker switches, I found that if I switched off the one that protects all the sockets in the house (except the kitchen), the RCD would stop tripping. So at least I knew the problem wasn't with the fridge, washing machine, dishwasher, etc.

There had been very heavy rain and thunder & lightning when it first tripped, so I'm presuming that must have caused it. The house is only three years old and I can't find any leaks anywhere. No dampness in the attic, both outside lights were completely dry. Could the lightning have somehow done it?

I switched that MCB on again a few hours ago, and everything seems to be working fine now. Whatever was wrong seems to have sorted itself out (or, if there was a leak, dried itself out). I can't really afford an electrician right now, but should I call one out anyway? Or just wait and see if it happens again? Even if it never happens again, I'm curious as to what might have caused it. I don't like leaving things unexplained. Just wondering if anyone might have any clue as to what could have caused it.

meercat

I would always check the immersion is turned off first
Then check if you have outside sockets or lights that are on your rcd

RayM

meercat wrote: »

I would always check the immersion is turned off first
Then check if you have outside sockets or lights that are on your rcd

The immersion was switched off. The outside lights are on a separate MCB, and the outside socket (which was completely dry anyway because of the way the wind was blowing) is on the kitchen MCB, which was fine. The main switch stopped tripping when I switched off the MCB that controls all the other sockets in the house.

I forgot to mention in my previous post that I have rooftop solar panels. Could the lightning + solar panels have had anything to do with it, maybe?

2011

To solve this problem it helps to understand how an RCD works.

When a circuit is functioning correctly the current flows down the phase (live) conductor and returns on the neutral conductor. From here it returns to the start point of the transformer that supplies the installation.

However if the current flowing through the phase conductor is greater than the current flowing inn the neutral conductor then the "missing" portion of the current has found an alternative another route back to the star point of the transformer that supplies the circuit. This only happens when the circuit is not working in a safe manner. Theoretically this current could be flowing through a person (being electrocuted) and from there back to the star point.

Let's assume that the current flowing through the phase of a circuit is 6A, the current returning throughout the corresponding neutral is only 5A and the protective device (fuse or MCB) protecting this circuit is rated at 10A. In this case the protective device will not operate. This is not a desirable situation when we consider that a 50mA current passing though a person is potentially lethal :eek:

So some bright spark (pun intended) invented the RCD. It measures the magnitude of a current supplied to a given circuit (or circuits) and compares it to the current returning on the neutral. If there is a difference in excess of the rated value (generally 30mA) the device will operate. A single RCD that supplies multiple circuits (such as one protecting several socket circuits) it will have multiple MCBs and returning neutrals associated with it. This is why an RCD often has a dedicated neutral bar, hence two neutral bars in most domestic installations. Connect a neutral to the wrong neutral bar and this causes a current imbalance and the RCD trips.

Frequently RCDs trip when something gets wet. This may cause a small current to return through an earth due to moisture effectively reducing the insulation resistance to earth.

To find out what is causing an RCD to trip is a process of elimination. What I would do is:

1) Find out what is supplied by the RCD. This will narrow your search.

2) Switch off all MCBs fed by the RCD. Turn on the RCD. If it does not trip turn on the MCBs one at a time. One MCB may cause the RCD to immediatley trip when switched on. This may identify which circuit is causing the problem. Investigate each point on this circuit.

3) Failing that and only because I am trained I would disconnect circuits one at a time from the distribution board to identify the culprit. However we have now gone far beyond DIY.

Try one and two above and let us know how you get on OP.
Know your limitations!
If in doubt employ the services of a qualified electrician.

Sir Arthur Daley

2011 wrote: »

3) Failing that and only because I am trained I would disconnect circuits one at a time from the distribution board to identify the culprit. However we have now gone far beyond DIY.

Try one and two above and let us know how you get on OP.
Know your limitations!
If in doubt employ the services of a qualified electrician.

The op said he don't know much about electrics, i appreciate you mentioned try 1 and 2 of your fault finding guide but as we all know if further ideas are mentioned one can be sure they will try it. People will always try to exceed their limitations.
Not alone could they be putting their life at risk working where a lethal voltage is present but its also illegal.

Bruthal

Sir Arthur Daley wrote: »

but its also illegal.

How awful. Once you break a speed limit or two, or pay your tv licence a few days late, your conscience eases about connecting an MCB.

Bruthal

RayM wrote: »

I don't know much about electrics, so apologies if I use any incorrect terminology...

I woke up this morning to find that none of my sockets were working. I reset the main RCD switch and it immediately tripped again. So I unplugged everything in the house and tried again. Same thing happened. When I went through all the smaller circuit-breaker switches, I found that if I switched off the one that protects all the sockets in the house (except the kitchen), the RCD would stop tripping. So at least I knew the problem wasn't with the fridge, washing machine, dishwasher, etc.

There had been very heavy rain and thunder & lightning when it first tripped, so I'm presuming that must have caused it. The house is only three years old and I can't find any leaks anywhere. No dampness in the attic, both outside lights were completely dry. Could the lightning have somehow done it?

I switched that MCB on again a few hours ago, and everything seems to be working fine now. Whatever was wrong seems to have sorted itself out (or, if there was a leak, dried itself out). I can't really afford an electrician right now, but should I call one out anyway? Or just wait and see if it happens again? Even if it never happens again, I'm curious as to what might have caused it. I don't like leaving things unexplained. Just wondering if anyone might have any clue as to what could have caused it.

If there are RCD protected circuits heading outside, and tripping following heavy rain, that's the first place to look.

If you get double pole switches fitted inside the house to switch off any circuits that go outside the house, they make isolating such wiring simple, which is very useful when such tripping problems start, since circuits outside can be compromised by water.

2011

Sir Arthur Daley wrote: »

The op said he don't know much about electrics, i appreciate you mentioned try 1 and 2 of your fault finding guide but as we all know if further ideas are mentioned one can be sure they will try it.

The purpose of an electrical forum is for electrical discussion.

If providing electrical information is something that should not be done on the basis of safety then surely the same logic should be applied to other areas such as scuba diving, most types of engineering, rock climbing, sailing, parachuting, sky diving, welding, car mechanics etc.... the list is endless.

People will always try to exceed their limitations.

Keeping people safe by keeping them ignorant is not likely to work very well.
All of the technical information provided in this forum is already provided elsewhere on the internet.

they be putting their life at risk working where a lethal voltage is present

You say this as though you have not read my post properly.
If you read the part of my post that you quoted you will see that it is overflowing with warnings and states clearly states where the DIY boundary lies.

its also illegal.

We are not here to police the electrical industry.
However the forum guidelines does explain the legalities.

Mod warning: No more dragging this thread off topic.
If you do not agree with sharing electrical information then this is not the forum for you. Please discuss this view elsewhere.

2011

Bruthal wrote: »

If there are RCD protected circuits heading outside, and tripping following heavy rain, that's the first place to look.

Agreed.

If you get double pole switches fitted inside the house to switch off any circuits that go outside the house, they make isolating such wiring simple, which is very useful when such tripping problems start, since circuits outside can be compromised by water.

Good idea.

Best of all (but it costs more) is to have an RCBO per circuit rather than an RCD protection multiple circuits. That way if it operates only one circuit is lost. An RCBO is a combination of an MCB and an RCD.

Sir Arthur Daley

RayM wrote: »

I switched that MCB on again a few hours ago, and everything seems to be working fine now.

What sockets or what electrical item(s) were not working when this mcb was switched off?

RayM

Don't worry - if it involves anything more invasive or complicated than flicking switches, I'm not going to try it. My grandfather was an electrician, and if I learned one electrical-related thing from him, it's to always err on the side of caution, rather than trying anything potentially risky. Few things annoyed him more than stumbling across the consequences of botched DIY electrical work carried out by people like me.

Everything's still working fine today, but by switching off all the individual MCBs yesterday, I narrowed it down to the one that protects the sockets in the sitting room, hall and bedrooms (I had unplugged everything and switched all the sockets in the house off individually, but that didn't stop the tripping). When I switched that MCB off, everything else was fine. I switched it back on later in the day, and it didn't cause the RCD to trip again. I presume that would support the water theory, but there was definitely no sign of any water in or around the outside lights or socket, and no sign of any leaks in the attic or elsewhere.

The RCD did its job, so there isn't any safety issue. I suppose I'll just have to wait and see if it happens again, rather than calling an electrician out and having him potentially spend hours trying to trace a problem that seems to have resolved itself (for now, at least).

mikeyjames9

RayM wrote: »

Don't worry - if it involves anything more invasive or complicated than flicking switches, I'm not going to try it. My grandfather was an electrician, and if I learned one electrical-related thing from him, it's to always err on the side of caution, rather than trying anything potentially risky.

i don't think it's illegal to talk about fuseboxes yet..

but you never know what's around the corner

scudo2

mikeyjames9 wrote: »

i don't think it's illegal to talk about fuseboxes yet..

but you never know what's around the corner

Correct me if I'm wrong guys.

But I was led to believe any DIY work/opening a fuse box cover is now off limits to non electricans, even for myself, a P&H RGII.

I still think it's good to explain everything in laymans terms, and point out the limits a OP can check and do legaly.
Even after 30 years in the trade I have gained helpfull knowledge from reading boards.
For that I thank you all.
M.


The down side been:
"knowledge can be a dangerous thing"
So we still have to be cautious with what
we say.

A homicidal 8 year old could be giving advice here for all we know.

Last year a slightly deranged, so called plumber who was giving out advice on a medical forum for severe chest pains !!!!

Funny, if was not so serious.

mikeyjames9

good information and knowledge sharing is ok

wiring instructions to unqualified persons is bad

Bruthal

scudo2 wrote: »

Last year a slightly deranged, so called plumber who was giving out advice on a medical forum for severe chest pains !!!!

Once he was a plumber, someone here would have thanked him:pac:

akaMrSmith

Something to keep in mind, RCD's have a test button. The reason for this is that they are a mechanical device. It you dont use the test button the mechanism will seize over time. If its an old RCD this could be your problem. The test button is put there for legal reasons, if you dont use it you have no claim should something go wrong. Id call a spark to check this one.