100mA RCD Keeps tripping...

Castiel

Castiel

Castiel

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my RCD for the main supply keeps tripping for no apparent reason, it will not switch on for several minutes (about 5-10) then it comes back on. This happens at irregular intervals, sometimes several times a weeks and then sometime not for months.

The RCD is relatively new (6 years old)...

Ideas?


Thread title should be *keeps*, if a don sees this can you change it...thanks.
 
Drier - by that I mean my washer drier has tripped mine a couple of times. I know it's that because it wont turn back on until I turn the drier off.
 
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Could be anything.. we had a light fixing that occasionally tripped and we didn't find that for ages. you're going to do some serious investigating. :(
 
We had something similar about 10 years ago, turned out that when new central heating was put in the electrician didn't disconnect the old thermostat so when the room temperature dropped the fuse would trip. Took ages to figure out.
 
Someone mentioned down the pub that too many things plugged in a socket can do it.

How true is that, even if the load is within limits?

what is the limit for devices plugged into a socket?
 
Turn off certain circuits if you can to isolate the problem.

all it means is their is unecessary current flowing through the neutral causing it to trip. if you want to find out what's causing it to trip unplug everything you can and then plug them back in individually until it trips.
 
Castiel said:
Someone mentioned down the pub that too many things plugged in a socket can do it.

How true is that, even if the load is within limits?

what is the limit for devices plugged into a socket?
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No, only thing that will do is cause an overload which will trip the MCB/Fuse not the RCD.
 
Castiel said:
Forgive me for being completely dumb about this, but what is the diffence between MCB and RCD.
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MCB Detects Overload and short circuit, RCD can only detect any excess current from the Neutral conductor, RCD's have only look for a balance between the current it's taking and the current it's returning.

It is quite hard to understand, but think of it as making sure that their is no current going to earth.
 
Unplug everything in the kitchen when you're not using them and see how it goes. Make sure you unplug them and not just switched off.

I used to do this as a full time job, and it really could be anything. Most cases was white goods causing the problem.
 
RobRX-7 said:
Unplug everything in the kitchen when you're not using them and see how it goes. Make sure you unplug them and not just switched off.

I used to do this as a full time job, and it really could be anything. Most cases was white goods causing the problem.
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In my house it was the kettle, but at random times. We only know it was the kettle, because since we got a new one, the RCD hasn't tripped once.
 
When I had this, some water had seeped underneath the gas hob which had a mains electric starter, causing an intermittent short and tripping the main breaks.
 
Unless you can narrow it down to an appliance by elimination, then this probably needs a spark on site to get to the bottom of (and even then, it might be tricky if its an intermittant problem and cannot be reproduced at the time)

When disconnecting things, make sure you unplug rather than switch off at the socket, a lot of sockets dont switch the neutral (and neutral earth faults are a common cause of RCDs tripping)

A 100ma RCD suggests a TT earthing system, and you can get some weird RCD faults with these (for example, its possible to have a latent fault in your house that does not trip the RCD, but if a certain fault occurs in another property fed from the same transformer [or an electrician conducts a certain test] that can then cause your RCD to trip out)*

* For these technically minded, a neutral earth fault on a TT system will, chances are not trip the RCD straight away (depending on loading on the system), however if an earth fault occurs in another property, or a loop test is conducted, the current following in the earthing path will create a volatage drop across the electrode at the bottom of the transformer pole (which can have an Ra as high as 21ohms), this volatage between neutral and earth will then drive a current through the neutral-earth fault in the first house and trip the RCD*
 
It's most likely to be a faulty device tripping it, but could be a faulty rcd. I guess you haven't done any rewiring recently?
 
Sinny said:
MCB Detects Overload and short circuit, RCD can only detect any excess current from the Neutral conductor, RCD's have only look for a balance between the current it's taking and the current it's returning.

It is quite hard to understand, but think of it as making sure that their is no current going to earth.
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Clearly as you don't understand how an RCD works tbh!
An RCD use's a differential current transformer to detect the current balance going out of the Phase conductor and returning via the neutral, obviously this should always be equal/sum of zero in an electrically sound ring final/radial.
It's extremely rare for their to be ''unecessary current flowing through the neutral'' as this would require an extra circuit or external influences to create this magical 'extra current'
The vast majority of the time RCD's operate by detecting LACK of current in the neutral.
 
( |-| |2 ][ $;17688560 said:
Drier - by that I mean my washer drier has tripped mine a couple of times. I know it's that because it wont turn back on until I turn the drier off.
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This has made my brain explode.

If it's your drier causing the trip, surely the drier is then off anyway as it has no source of electricity
 
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