RCCB tripping

[mattice]

The RCCB (80A, 30mA trip) in our meter box keeps tripping. Given it's an intermittent fault I've avoided an investigation and with a 2 week holiday looming and on average once per week trip, it's time to do something about it.

I've monitored it for about a year (dabble with home automation) and I've recorded dates and times of trip and monitored power consumption on obvious appliances such as boiler, washing machine, fridge etc. I've found no correlation. When we last went on hols, I literally switched everything off (at sockets not consumer unit) apart from the fridge and within a couple of hours it tripped. We arrived back to a smelly flood.

Do these RCCBs fail? Would it be sensible to drop in a replacement and see how we go? I have limited test equipment (a decent multi-meter only). Anything straight forward I can investigate or should I just call a pro?


Thanks,

 

[333rocky333]

Does your decent multimeter have a clamp that can measure milliamps that you can clamp round your earthing lead WITHOUT actually disconnecting it.

Unfortunately some so called "Pro's are not good at finding intermittent faults

 

[deadshort]

Hi,

You may have an Earth Neutral fault which could be any where on your installation. Unless all your switches are double pole it will be difficult to trace without the appropriate test kit.

You need to unplug all your appliances,not just switch off at the socket and see if you get a trip.
The usual culprits are exterior sockets and lights which have moisture or water in them.

And yes they do go faulty !

Regards,

DS

 

[JohnW2]

Unfortunately some so called "Pro's are not good at finding intermittent faults

I don't think it's fair to blame them - it's the very nature of intermittent faults that can make them a nightmare to locate/diagnose - and that applies to "pros" and amateurs alike (although the latter generally have the advantage of being able to devote much more time to the task).

Given that RCDs can become faulty, and given the large amount of time/effort that can be involved in hunting for an intermittent fault, I would personally always start by (properly) testing the RCD and (since even 'passing the test' doesn't necessarily preclude an intermittent fault in the RCD) maybe even temporarily replacing the RCD before embarking on the 'hunt'!

Kind Regards, John

 

[ericmark]

I fitted two RCD's back in around 1992 and they have tripped for no good reason many times. But not all RCD's are equal the X-Pole for example claims not to trip until 90% of the 30 mA is drawn when most trip anywhere between 50 ~ 100% also the X-Pole has a warning light when leakage is getting near the point where it may trip. Plus it is claimed more resistant to spikes.

However my mother had 4 RCBO's installed in he kitchen and they have never tripped so as to if a more resistant to spikes RCD or smaller circuits it the better it's hard to say.

Personally if the consumer unit will take RCBO's then I would say that is the way.

There was a very expensive auto resetting model

Untitled

• ericmark
• 6 Dec 2008
• 34

but it seems these are no longer permitted in domestic.

Early RCD's like mine had no electronics in them and were very prone to tripping latter ones did have electronics and are less prone but as far as I know there is no way to test with even a standard RCD tester on how prone any RCD is.

Of course however good the RCD is with 30 mA leakage to earth it must trip. Some meters will measure this but as far as a holiday goes then really the only thing plugged in is your fridge freezer so can't see how measuring really helps? In fact I note when resetting my trips try switching on the sockets first often it trips but try switching on lights and cooker first then the sockets rarely trip the RCD so having everything else switched off could do the reverse of what is intended.

Often it is in fact the freezer at fault an element used for de-frost is only switched on a few times a day so a faulty one can be near impossible to detect. The main way is to swap the RCD it is being fed from and if the fault swaps then you know freezer is at fault.

I know my neighbour had intruder alarm on same circuit as freezer the battery in panel would last about 2 hours so if power off for more than 2 hours the bell would ring and a neighbour with key would investigate.

Other than that insurance is the only way.

As to testing the RCD I have done that and no fault shown. Also tested circuit again no fault found. Changed RCD and it stopped tripping and yes did test new on to show it did trip at 30 mA. Simply one was more resistance to spikes then the other.

 

[ban-all-sheds]

Don't have the F/F on an RCD circuit - sorted.

 

[mattice]

Good point about unplugging appliances, now I feel stupid.

Sadly my decent multi-meter doesn't have a current clamp but thanks for the tip on outdoor sockets. I think you might have something there as I recall constantly tripping the RCD on the consumer unit when using my circular saw, I guess that would trip before the RCCB in that scenario.

I've ordered a new RCCB, and called an electrician who I've used before. He mentioned a ramp test on the existing device and testing the obvious circuits (now starting with the outdoor socket, thanks).

Thanks for the replies.

 

[deadshort]

Can I ask is it a Crabtree unit ?


Regards,

DS

 

[mattice]

Yes Crabtree 528/030

Ordered a 2 pole replacement but couldn't find this part number, and having received it, it's got exposed electrical parts rather than being panel mount. Damn.

 

[ban-all-sheds]

What do you mean?

 

[mattice]

To close off the thread.

Electrician around today, RCCB tripping at 16mA so replaced with the above replacement.

I didn't realise there were terminal covers on the old device which simply slotted onto the new device.

Job done. Interesting (for me anyway) that washer, tumble drier, and dishwasher each had 4mA leakage... all new appliances.


Thanks for the guidance

 

[Iggifer]

4mA is nothing really, if you were to get a shock of 4mA, it's just above the point where it is only a tingling sensation, and starting to become uncomfortable.

A typical PC leaks about 3mA, and uses much less power than something with a heating element in it.

 

[JohnW2]

4mA is nothing really, if you were to get a shock of 4mA, it's just above the point where it is only a tingling sensation, and starting to become uncomfortable.

That's true, but not really in any way related to the fact that the OP's kitchen appliances each leak about 4mA to earth (which is pretty typical of things with electronics).

Kind Regards, John