nuicance tripping on consumer unit.

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sigma | 11:45 Sun 02nd Nov 2008 | Home & Garden
9 Answers
My consumer unit appears to suffer from what can only be described as "nuisance tripping". The unit is fitted with RCD's and can trip at any time of day or night regardless of what appliances are connected. Has anyone any ideas of how this can be overcome.


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I have people ring me all the time about the same problem as i'm a self employer sparky so here's what it could be, kettle, iron, microwave, fridge, freezer, dishwasher, washing machine or anything plugged in with an earth attatched to it & the only way to find out what it is is to unplug one of the items and see if the RCD carries on tripping out during the day or night, when I say unplug I mean don't just switch it off at the plug socket as the neutral is still connected and can trip the RCD even tho the appliance is not on and 9 times out of 10 it is the appliance that has water in it.

When I say anything with an earth it wont be a TV, radio and anything else with a 2 core cable as these appliances are double insulated and haven't got an earth.

Let me know how you get on....
It's overload....what have you recently plugged in?
I agree with Disco, it is probably some appliance that has water in it some how, or the cooker (if you have electric cooker that is) washing machines, fridges etc should ideally be connected via spur units so that they don't have to go through the rcd side of the unit. sometimes though it could be an over sensitive rcd, but this is quite rare.

PS. The problem that occurs with Kettles,cookers, showers etc, is that once they are over about 1 year old, the casing on the elements in them start to wear and may have a very fine hairline crack in them, the rcd thinks it is a fault, so trips, if they were not going through rcd, they would still be working fine.
Terambulan, if you had even the SLIGHTEST idea of domestic electrical installations or how RCDs work then you would know it ISN'T overload. MCB's protect against over current conditions - not RCDs, they protect against fault currents. If the current traveling in the phase (live) and neutral lines isn't equal (when there is a fault to earth for example) then the RCD will trip.

As Disco says, something is causing this imbalance and it won't be something without an earth connection. Favourite causes would be a fridge/freezer or something else with a thermostat on or anything with an heating element.

As a fellow sparks then I can confirm that these are the most time consuming jobs - customers rarely realise just how many causes of nuisance ripping there could be and only a process of trial and error will find out which it is.

For me, Ray has put his finger on the most likely cause - a faulty element in something - cooker or kettle or shower.
There is a good chance that over time the nuisance tripping will become more frequent � making identifying the offending circuit easier.

Besides the likely electrical items named by others, I would add to the list, your central heating pump as a potential candidate.
Raysparks is right and disco is right and as for terambulan he is wrong.

An rcd works in a different way from a fuse or a circuit breaker an rcd also trips when there is a fault between neutral and earth and it is nothing to do with overloading.

I have even known low energy light bulbs to trip out rcd's and as ray knows now that the 17th edition regs say that the lighting circuits should be on a rcd or a rccbo (which is esentialy the same as an rcd) so now the new regs have come in I suspect that in the future we will have loads of problems with low energy bulbs doing this
God I did not realise that there were so many fellow sparkies on here and lcdman I agree with you sometimes it is very hard to try to explain to the customer that it is their appliance doing it after you have rewired or put a new board in.

Well it was working ok before
I agree with LCDman and Knobbynits.
Ive changed countless fuseboards with a split RCD board and the amount of times I get the usual phone call saying 'it keeps tripping out whan I do the ironing' so I tell the customer to get a new iron even tho it is probably only 6 months old and that they should have kept the receipt....
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Thanks everyone, it's a pity the tripping isn't more frequent as it would make it easier to eliminate the cause. Looking at the age of the appliances, the fridge/freezer seems the most likely culprit.

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