RCD tripping - really odd!

OK - here's the story - long one - be warned!!

Just had kitchen done - had to have a partial re-wire owing to things found during the kitchen works - nothing major - just had to work out how it was wired and run a new ring for the kitchen and break the existing ring to drop the kitchen ring into it.

It was all done by a very experienced electrician - who also is a Corgi regd plumber and fitted our new combi boiler.

Fuse board is not that new - but not that old. Has a 100mA RCD protecting everything.

1 sockets ring for whole house (12 outlets), upstairs lights, downstairs lights, shower (now whirlpool bath), water heater (now feed to combi boiler) and cooker.

Up until boiler/kitchen works we had *not* troubles with the RCD tripping.

Now we have random drops of everything. No individual cct trips - just the rcd drops everything out - in fact it just did it - which spurred me on to write the mail. Last time it did it was just after we went to bed and we woke up 10 hours later to find most of the freezer contents too defrosted to save :(

It was a bit of a PITA when the kitchen was done as the damn thing kept tripping all the time - even before the ring was broken to insert the new kitchen works.

Now the works are all completed - and everything appears hunky dory. We had DP above surface switches installed to the appliances when they were moved into their new homes in the kitchen so they can be totally isolated.

However, twice now - when it has got "damp" outside - the RCD has dropped out.

I just don't get it.

The sockets CCT was tested as part of the works done - as was the cooker cct as was the re-use of the water heater cct.

The following items were plugged in and operating at the time: TV/VCR/DVD recorder/DVD player/Sky Box - TV and Sky on - rest on standby Phone Computer and monitor Fridge/Freezer Some lights downstairs and upstairs

These were connected and power was live to them, but they were "off" at the machine: Washing machine

The electrician suggested it's most likely to be one of the white goods - but - since the only one plugged in was the fridge (and the washing machine - but it was "off" at it's controls) I can't understand how....

Now - my mind says - the obvious thing is the roof is leaking water into the roof space and water is getting into the lighting wiring - but - if that was the case - the short would probably mean that I wouldn't be able to re-set the RCD immediately - and it would drop out again - but it can be re-set straight away.

The electrician said to work it out we need to keep things off and gradually add them into the equation until we find something that causes the trip. But - since the last one was 12 days ago - it's not going to be a quick exercise to work out what gives.

Anyone got any suggestions? I just read an old thread on here about a replacement of an old fuse board with an RCD protected board and similar things happening - and that referenced the fridge drain onto the electrics - so I'll go and check that now - but - otherwise I'm stumped!!

Help? I'll check the lighting ccts in the loft tomorrow morning - but I was up there the other day and there was no sign of water damage anywhere - so I doubt the roof is leaking.

I don't want to go the re-wire route if the RCD is a bit dicky - and I'm a bit stumped for how to work out the culprit. Can you totally test all the wiring in the house without too much invasion to prove the circuits are all OK - so we at least know it's an appliance that's at fault? If so - does it take long and is it particularly costly? Likewise for testing the RCD.....if the RCD is stuffed he has already told me that they no longer make the one in the unit - only a 30mA trip one that isn't going to fit in the existing chassis - so it's a new box and bits.....We've just shelled out a lot on the boiler/kitchen works - and to have this on top is just not fair :-| (although it's bloody typical!!)

Any advice gratefully received.

Cheers Dan.

Reply to
Dan delaMare-Lyon
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If you can get a isolator to swap the RCD for, you could then just get a double enclosure for a new RCD, that would be the cheapest way to go.

We had an RCD die a few years ago, it just went super sensitive and would trip randomly, and also if the tumble dryer was switched on.

We knew an electrician with an RCD tester, he confirmed this was the case - maybe you can find someone with one?

Sparks...

Reply to
Sparks

Now there's the rub: you want a magic box that when plugged in points to the cause of the problem (I guess we all would want one of those in the same circumstances). This issues is being debated in another thread here just now, so there may be useful stuff there.

My reason for posting is to float an idea and watch the others tear me to shreds.

If nuisance tripping is an annoying problem, how about having a consumer unit that is a split-load and on the unprotected side have a separate RCD (or RCBO) for a SINGLE circuit?

To find the source of the trip (i.e. which of the circuits on the mainRCD is causing the problem, presuming its only one) then you would methodically re-wire each circuit through the additional RCD and then leave the circuit for some time to see if it trips separately.

You did mention (IIRC) that you have included your kitchen in another ring main loop - I wonder whether that's the best idea for a kitchen because if any of the appliances are dodgy it will take out the whole house instead of a separate RCD.

Yup, just went to City Electrical Factors and bought a RCBO for the new conservatory - I nearly collapsed when the bloke said =A347 or so!

HTH

Mungo

Reply to
Mungo

Hmm thanks for that. I'm pretty convinced that - given the fact there have been no problems in 6 years - and now the ring main has changed and has been re-tested - it's the RCD being ultra sensitive. Also I note that they are buggering about with the electics locally as they are tying in a new housing development up the street and the supply to the flats behind us - which they actually started the *day* we started the kitchen - so I think the two must be in some way connected. Still gonna check the fridge - but thanks for the suggestion about taking the RCD offboard - will try and get the RCD tested.

Every other cct has been checked - although - not under my ownership.

Cheers Dan.

Reply to
Dan delaMare-Lyon

Its usually caused by resistive leakage between the live and earth on any appliance. Such things as immersion heaters and cooker rings are prime suspects.

Of course you could have some leakage caused by water or damp somewhere in the system.

Another cause not that well known about is a short, well intermittent one, between Neutral and Earth so currents coming in through the RCD on the live are supposed to return through the RCD on the neutral. Oddly enough this won't cause tripping until some appliances are on and pulling some current.

If they don't for any of the above reasons, and get diverted off to earth somewhere.. then off goes the trip.....

Reply to
tony sayer

Sparkies have left you an neutral earth short is my guess.

Switch off the whole power, disconnect the neutrals to the new stuff, and see if one has a short to earth..chances are its something like a nick in the insulation in s steel backing box.

Dampness alone wont cause a 100mA trip to go, unless its straight across live wires.

Reply to
The Natural Philosopher

In article , Dan delaMare-Lyon writes

Thats doesn't seem good science to me somehow..

Wouldn't have thought that works on a new housing estate up the way would have anything to do with this. Bet theres an intermittent earth/neutral short somewhere....

Reply to
tony sayer

Mungo - dropped the "Two Sheds" now have we ;-)

Hell yes - plug it into one socket and it tells me what's wrong with the sockets - plug it into the lights - etc etc :)

Ta - is that the 30 vs 100mA RCD one?

That's Usenet for you ;-) You know you've arrived when you have a newsgroup named after you ;-)

Well that's what the electrician suggested replacing the system with citing one sockets circuit for the whole house as a somewhat bad idea. All the washing things (washer, dryer, dishwasher) were previously in the same corner - unbeknown to me - all plugged into sockets on a spur - now fixed ) - but with it all on the one - it's a bit of a pisser. *however* - thanks to the design of what we have just done - if it became necessary - we could make upstairs and downstairs rings with relative ease :)

Yup.

Actually - I think I'll borrow a Fluke from the office and check the between rails figures on each of them. I can't help but think it'll be the sodding fridge or dishwasher at fault - owing in part to the fact they saw their friends mr washer and mrs dryer replaced with nice shiny new units late last year - bet it's one of them.

I'll give the whole lot a thorough once over tomorrow and over the weekend. I can get at most of the wiring or have seen it in the last couple of weeks what with all the work that we've had done - so - know where it all is and how it's connected now - so - at least I'm learning as I go!!

Bugger - was that the premium one that had added "feel good"? Have you looked in screwfix lately - they do a Crabtree whole kit for 60 notes or something bonkers like that. Makes me feel a little easier about the cost :)

Yup

Ta. dan.

Reply to
Dan delaMare-Lyon

No immersion any more - replaced with Combi boiler - and the immersion cct fused in-line to run combi - hmm - come to think of it - problems really started once that work was done - but the CCT was tested and was fine - but that was of course before it was connected to the boiler.....I *wonder* if the boiler is causing a fault?! Bugger - how do you test for that.....it really is random - the only remotely common things being a) night time and b) moisture in the air (1st time freezing fox, 2nd time rain as tonight)

Will check this over tomorrow.

What would the fault become a function of then - as I can load up the system by running every damn thing we've got at once and that doesn't seem to cause any problems.....

Hmmmm - i'll monitor it.

Cheers dan.

Reply to
Dan delaMare-Lyon

Well - one other thing I now recall is that the electrician had trouble getting the RCD to latch on once he had replaced the boiler and re-fused the old immersion cct to run the boiler - reckoned it took him something like 20 odd operations to get it to stay on and not trip out. Given that nothing else changed in the works other than removing the old power feed down the wall to the boiler from the junction box in the floor under the airing cupboard - adding a new run of cable to the old outside loo - adding a fused switch - and connecting it to the boiler - *then* he had those problems - that might actually suggest it's something in that area - didn't think of that.

Well I was reading an old thread on google groups archive and that suggested that RCDs tend to trip on inbound voltage fluctutaions - plus on earth changes. Just clutching at straws at the moment :)

You reckon I should start with the white goods - check them first?

Cheers dan.

Reply to
Dan delaMare-Lyon

Errr, never had it in the first place. Although my forename is unusual it isn't unique to me and you are confusing two Mungos! No offence taken - my catchphrase is "daft name, goes with the face".

Aye (I think).

In your other response you said that there was works elsewhere in the street. Someone said (here, in the last couple of days) that such works can cause RCDs to trip in other houses. Though several things have changed, I wouldn't rush to blame external factors since you have done a major upheaval on your electrics. Possibly something you've overlooked.

Hope you get a cure (and when you do a Reply here would be nice!)

Regards

Mungo Henning (crikey: bet there's another beyond my old man ;-)

Reply to
Mungo

My Bad - mixing you up with another Mungo on another group :) You don't happen to have "two sheds" do you ;-) You could keep the name then :)

Been reading 2 others...

See my other posts - I've been thinking and a couple of other things have come to mind - and a couple of other suggestions made. Looks like it's time to get the meter out and start with the obvious things (the new works) and then go bcakwards from there. SOD IT - I didn't have enough time to finish the job before the out-laws visit anyway - let alone with this to add to the equation :)

Dan.

Reply to
Dan delaMare-Lyon

In article , Dan delaMare-Lyon writes

Possibly might be, a bit of muck or something causing some leakage. Its where I'd start to look. Could try running the boiler of a supply from elsewhere that isn't RCD protected but ISTR that you had the whole place on RCD?. If you've got a UPS of sufficient capacity you could run it off that, at least that would supply current that wasn't RCD'ed as it were...

See in another thread that the bloke had some problems in resetting the RCD and had to try many times. That indicates to me that something went wrong when he was working on all this. Having to push the RCD many times to reset isn't right!. He should have done something about that and not use a bigger RCD!.....

Then I "doubt" its that.

Reply to
tony sayer

I have a "random" problem, ( about one trip every two months) that seems to have a fairly high correlation with it raining... I suspect water is getting in to an outside light when the wind is in a certain direction .....

The way I intend to try to find it is to put each circuit on to an RCBO, taken off the split CU that is RCD protected.

At the moment I have the lights with no RCD protection, the fridge / freezer on a separate RCD and the rest of the house on two separate RCD protected circuits - so the trip is just a PITA and doesn't cause the agro of a defrost or lights going out.

As you comment, if its a while between trips, its a long process to fault find....

Nick

Reply to
Nick

Which would suggest he would have had an RCD tester... did he test it?

OK - pretty sub optimal for the reasons you are now discovering!

Firstly before we go much further - do you need a RCD covering the whole house? (i.e. do you have a TT supply (i.e. one with a local earth spike and no earth provided by the electricity supplier)).

Strewth! Hope you havn't got too many mod cons in the kitchen then!

Which suggests that somewhere along the line something has shagged a cable or a connection.

well you would do if the RCD protects all the circuits! (the individual circuit fuses/mcbs will only protect from an overcurrent fault - not an earth leakage one)

So damage to an existing cable perhaps...

Any outside electrical fixtures?

Tested in what way? Just R1 + R2 loop impedance, or insulation resistance as well?

Things with heaters in are often good candidates...

Not necessarily. Your fault may be causing fairly steady and large leakage that is using most of your 70mA or so budget (a 100mA RCD will probably trip at about 60 - 70% of its marked rating). It then only takes a small transient change in leakeage elsewhere to cause a trip.

You need to get some basic checks done, and if that does not find it, you need to start being methodical.

You can do a bunch of simple tests with just an ordinary multimeter to start with.

e.g. turn off the power, open the CU and disconnect both ends of the socket circuit from the fuse/mcb and the neutral bus bar. Make sure everything is unpluged form the circuit. Now set you meter to a high ohms range and measure the resistance between Live and Earth, and Earth and Neutral - both readings ought to read as infinite or open circuit. If they don't you have your problem. To isolate a fault location you can do a "binary chop" on the ring - i.e. break it roughtly in the middle at a socket and test to see which half has the partial short. Keep bisecting the remaining circuit until you isloate where.

If the first circuit is ok the reconnect it and try another.

Once you have eliminated the wiring itself (which you won't be able to do for absolute certain with a ordinary multimeter (you need a megger tester to be sure) but you can do with a reasonable degree of confidence), you can set about the appliances. Again you can try a binary chop - unplug half of them and see if it still trips etc.

I would start looking closer to you most recent changes - i.e. the kitchen.

yes - firstly see above (better still if you can borrow a megger). You can also disconnect all the loads in the house and use a RCD tester to see that the RCD is doing its stuff. In fact an RCD tester can be useful for finding a dodgy appliance. Since you have a 100mA RCD you could hook the tester up to a socket and test with a 50mA trip current. The RCD ought not trip. Plug some appliances back in and re-test. This can show you which one is adding a significant amount of leakage. You are not measuring the amount of leakage - but you are seeing how much you need to add to it before pushing it over the limit.

Being realistic - you would be better off making changes like this anyway. Assuming you are not TT (where you require RCD protection on everything), a split load CU with lights and most other stuff on the non RCD side and only the required circuits on the 30mA RCD side would make much more sense. Splitting the kitchen off into its own ring circuit would also seem prudent, and also providing a dedicated non RCD feed for the freezer.

Reply to
John Rumm

He did not - as he didn't have the kit with him.

Washer, Dryer, Dishwasher - that's it.

I would tend to agree thinking about it. He's coming back to do the final tests for the new ring before issuing the paperwork anyway - so we can follow up then.

Unlikley - as nothing existing has been moved - in fact - the existing has been removed if you like - as the old cable that formed the middle of the circuit was taken out to put the kitchen ring in and two spurs were disconnected to bring everything in line.

1 outside light - security one - will check it today - ofc I didn't put 2 and 2 together and realise that it could be the outside light. Perhaps I should remove that for a couple of weeks and see what gives :)

Yes to all 3.

Now would they cause this if they were plugged in and power was live to them - but they were off at the controls on the front?

Rest read and absorbed - will talk to electrician soonest - but am off to get a better meter first.

Cheers dan.

Reply to
Dan delaMare-Lyon

Dan delaMare-Lyon wrote: Well - one other thing I now recall is that the electrician had trouble

Immersion heater elements are always a first port of call. As are outside runs of cable..

Reply to
The Natural Philosopher

However, when you have a large amount of earth to live capacitative coupling, its entirely possible for a voltage spike in the incoming mains to cause an RCD to trip.

My 30mA used to trip EVERY time the overheads got blown together, or a branch fell onto them, or a lightning strike hit them

Now its only about 30% likely to happen with a lightning strike.

So do NOT entirely disregard things like that.

The trouble is that todays tight RFI specs and the tight electrocution specs run into each other in this area.

Reply to
The Natural Philosopher

Just pulled the test sheet for this cct at the changeover 3 weeks ago. It's a straight run with 1 join where it was re-pointed in the now defunct airing cupboard. R2 is 12 ohms Phase/Neutral - >30Mohm Phase/Earth - >30Mohm Neutral/Earth - >30Mohm Max measured earth fault loop impedance 0.34 ohm

18ms operation time for RCD at I-delta-n - 48ms at 5I-delta-N

All passes tests OK.

Could that relaly still be it.

There aren't any *except* to an outside light - which - predictably since it's not pissing it down today - I will pour water over and see if I can re-create :)

Cheers Dan.

Reply to
Dan delaMare-Lyon

FWIW, In my recent experience with a leaking pipe causing the RCD to randomly trip, it could be reset immediately each time, so don't write that cause off yet.

Reply to
mark_yh

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