RCD a pain!

sparkfireman

Called to my mates to do a nixer... she said the toaster kept tripping the RCD, so she replaced the toaster...

It keeps tripping...
Socket is fine...
Other appliances, kettle, blender etc works fine...
Its not a case of overloading as it was the only thing operating...
In a kitchen Ring socket....
Fuse board a mixture of MCB's and Old Fuses.... (not my work!)

Any suggestions appreciated...

Thanks guys

M cebee

nothing rings a bell with me anyway

changed toaster -it still trips-other appliances works fine in same socket


you can safely rule out overload-on an rcd:pac:

assuming new toaster is ok
i'd prob ramp test the rcd and check leakage current

IR test outgoing side of rcd at 250V between L+N( joined) to earth without disconnecting appliances-to get an idea

and do a full IR test


another option is to rcbo the kitchen ring if you need to narrow it down

Bruthal

sparkfireman wrote: »

Called to my mates to do a nixer... she said the toaster kept tripping the RCD, so she replaced the toaster...

It keeps tripping...
Socket is fine...
Other appliances, kettle, blender etc works fine...
Its not a case of overloading as it was the only thing operating...
In a kitchen Ring socket....
Fuse board a mixture of MCB's and Old Fuses.... (not my work!)

Any suggestions appreciated...

Thanks guys

As m cebee says overload wont trip an RCD by itself, plug everything in the house out and see does it reset, if not then switch off all MCB`s controlled by the RCD and see does it reset, if it does, switch them all back on, if you come to one that trips it then problem might be on that circuit.

If its a neutral earth fault then the RCD wont trip with all MCB`s on and all items plugged out, will usually trip when you plug something into the problem circuit,

If its a faulty item then this will show up when you plug each item back in, and operate the item.

How did you verify if the kettle and other appliances are all fine if the RCD keeps tripping? Did you try them in a different circuit? This info would help maybe

I switched off main power in a house before and the RCD still tripped, which would make you think the RCD was faulty but it was not the RCD at fault.

After that do the test suggested by M cebee,

2011

It could be a faulty RCD. If you don't have an RCD tester to hand plug the new toaster into a socket protected by a different RCD (such as a neighbors house) and see what happens. If it causes another RCD to trip chances are it is another faulty toaster. If it doesn't the chances are the toaster is OK, push the test button on the second RCD and see if it operates.

Bruthal

2011 wrote: »

It could be a faulty RCD. If you don't have an RCD tester to hand plug the new toaster into a socket protected by a different RCD (such as a neighbors house) and see what happens. If it causes another RCD to trip chances are it is another faulty toaster. If it doesn't the chances are the toaster is OK, push the test button on the second RCD and see if it operates.

Removing the outgoing live and neutral links from the RCD and see will it then reset might show if its faulty. A faulty RCD is a good possibility alright.

Buford T Justice

I came across something like this once before when I was replacing an old fuse board with a new consumer unit. It transpired that when some lights or other were being added into the kitchen they had no neutral for the circuit so they just tapped into the neutral from the sockets. Only turned up a problem with the new consumer unit when the RCBO was fitted, It was tripping every time the kettle was turned on, and only happened with the kettle. Might be worth considering there.

Bruthal

Fingers McGee wrote: »

I came across something like this once before when I was replacing an old fuse board with a new consumer unit. It transpired that when some lights or other were being added into the kitchen they had no neutral for the circuit so they just tapped into the neutral from the sockets. Only turned up a problem with the new consumer unit when the RCBO was fitted, It was tripping every time the kettle was turned on, and only happened with the kettle. Might be worth considering there.

I wonder how that was happening, it surely must of tripped the RCD when the added in lights were turned on, but how did the kettle now trip it?

If the lights were off then its just a neutral wire from the sockets going nowhere, assuming the lights were wired right, and if lights are turned on that itself will instantly trip RCD.
Must of been something else wrong with them lights.
Just curious.

maxamillius

came across some outside lights before that had the neutral tapped off kitchen socket,massive down pour one night and lights filled with water therefore tripping the rcd!

Bruthal

maxamillius wrote: »

came across some outside lights before that had the neutral tapped off kitchen socket,massive down pour one night and lights filled with water therefore tripping the rcd!

Again though, the light would never of worked with the neutral only taken from the socket, the live must of been from the socket also.

maxamillius

sorry robbie thats correct yes they were directly off a socket,it was actually an outdoor socket which was on the kitchen circuit!

M cebee

Fingers McGee wrote: »

I came across something like this once before when I was replacing an old fuse board with a new consumer unit. It transpired that when some lights or other were being added into the kitchen they had no neutral for the circuit so they just tapped into the neutral from the sockets. Only turned up a problem with the new consumer unit when the RCBO was fitted, It was tripping every time the kettle was turned on, and only happened with the kettle. Might be worth considering there.

it's called a 'borrowed neutral'


but those symptoms don't sound right


it shuda just tripped when light was switched on

Bruthal

M cebee wrote: »

it's called a 'borrowed neutral'


but those symptoms don't sound right


it shuda just tripped when light was switched on

Hmm i thought i just said that:eek:

M cebee

robbie7730 wrote: »

Hmm i thought i just said that:eek:

you did but i copied it

and pasted it it:D

Bruthal

M cebee wrote: »

you did but i copied it

and pasted it it:D

No harm in that, sure is`t that what i always do:)

SparKing

Had a similar problem before where there was a bit of nuisance tripping on a kitchen radial but it only seemed to trip when the toaster was used, not the kettle either, so I swapped out the toaster, assuming it was faulty, for a smaller one which seemed to be fine.
Was called back again the following week for more tripping so I ended up tearing the kitchen units apart to follow the cable and found a tiny tear on the cable which exposed the neutral copper and this because of dampness under the units seemed to be causing the tripping. Moral of the story is, follow Em Ceebees advice and megger the cable.
Also, a previous electrician had "fixed" the problem by bypassing the RCD entirely, cowboys Ted, they're a bunch of cowboys

Bruthal

SparKing wrote: »

Had a similar problem before where there was a bit of nuisance tripping on a kitchen radial but it only seemed to trip when the toaster was used, not the kettle either, so I swapped out the toaster, assuming it was faulty, for a smaller one which seemed to be fine.
Was called back again the following week for more tripping so I ended up tearing the kitchen units apart to follow the cable and found a tiny tear on the cable which exposed the neutral copper and this because of dampness under the units seemed to be causing the tripping. Moral of the story is, follow Em Ceebees advice and megger the cable.
Also, a previous electrician had "fixed" the problem by bypassing the RCD entirely, cowboys Ted, they're a bunch of cowboys

Ye could talk that into comin down ted.

M cebee

bypassing rcds:mad:

why do people do this when they can't fix it

i wouldn't call them electricians

johnnyjb

I changed an old fuse type board (no rcd) for a mcb board few years ago.

Few days later kitchen circuit was tripping rcd

An older socket was causing it, the neon light was trapped and shorted against the earth plate inside

296924.jpg

.G.

M cebee wrote: »

bypassing rcds:mad:

why do people do this when they can't fix it

i wouldn't call them electricians

They probably arent. Plenty of "handymen" do electrics.

that said I've worked with a fair few qualified lads who shouldnt be let near a pack of batteries let alone mains voltage

Bruthal

superg wrote: »

They probably arent. Plenty of "handymen" do electrics.

that said I've worked with a fair few qualified lads who shouldnt be let near a pack of batteries let alone mains voltage

Thats what big building booms do, a fella can drill a few holes and cut unistrut and thats it, he`s in demand.

sparkfireman

robbie7730 wrote: »

As m cebee says overload wont trip an RCD by itself, plug everything in the house out and see does it reset, if not then switch off all MCB`s controlled by the RCD and see does it reset, if it does, switch them all back on, if you come to one that trips it then problem might be on that circuit.

If its a neutral earth fault then the RCD wont trip with all MCB`s on and all items plugged out, will usually trip when you plug something into the problem circuit,

If its a faulty item then this will show up when you plug each item back in, and operate the item.

How did you verify if the kettle and other appliances are all fine if the RCD keeps tripping? Did you try them in a different circuit? This info would help maybe

I switched off main power in a house before and the RCD still tripped, which would make you think the RCD was faulty but it was not the RCD at fault.

After that do the test suggested by M cebee,

RCD only trips when toaster is plugged in.

Everything else runs fine....

if theres a neutral earth fault the RCD WILL trip with MCBs on!

Bruthal

sparkfireman wrote: »

RCD only trips when toaster is plugged in.

Everything else runs fine....

if theres a neutral earth fault the RCD WILL trip with MCBs on!

Not usually if there is no load on it wont. It usually wont trip if nothing is plugged in on the affected circuit with neutral earth short. On non neutralised installations its more likely alright.

Did you try the toaster plugged into a different circuit.

sparkfireman

Similiar off/on topic question.... Got a phone call just this minute and my head isnt right after an all nite house fire! :O

Jus outta bed...

But my mates immersion element keeps tripping RCD on BATH only...
His ma called an "electrician" friend of hers... who bypassed the RCD and immersion works fine on bath sink... etc....

How is this?? Is the whole tank live?

Cant think...

Someone answer

sparkfireman

robbie7730 wrote: »

Not usually if there is no load on it wont. It usually wont trip if nothing is plugged in on the affected circuit with neutral earth short. On non neutralised installations its more likely alright.

Did you try the toaster plugged into a different circuit.

toaster works fine...

Bruthal

sparkfireman wrote: »

toaster works fine...

Did you try a kettle in the same socket the toaster was tripping the RCD from, its a neutral earth fault alright by the sounds of it.

sparkfireman

robbie7730 wrote: »

Did you try a kettle in the same socket the toaster was tripping the RCD from, its a neutral earth fault alright by the sounds of it.

Kettle works in the same socket!

Bruthal

sparkfireman wrote: »

Similiar off/on topic question.... Got a phone call just this minute and my head isnt right after an all nite house fire! :O

Jus outta bed...

But my mates immersion element keeps tripping RCD on BATH only...
His ma called an "electrician" friend of hers... who bypassed the RCD and immersion works fine on bath sink... etc....

How is this?? Is the whole tank live?

Cant think...

Someone answer

The element likely has a fault to earth on it, usually that is caused by the element copper outer jacket splitting and some current flowing into the water to earth, or just a neutral earth fault somewhere within the immersion heater unit, a direct live earth fault would usually trip the MCB as well. The tank is unlikely to be live, but bypassing the RCD is nuts. Insane. Bypass and walk away,, job done??

Never ceases to amaze me the ``electricians`` that are out there

Bruthal

sparkfireman wrote: »

Kettle works in the same socket!

So the toaster trips the RCD in one socket, but does`t in a different one, and the kettle works ok in the one affected by the toaster?

sparkfireman

robbie7730 wrote: »

So the toaster trips the RCD in one socket, but does`t in a different one, and the kettle works ok in the one affected by the toaster?

Ok...

Kitchen ring socket....
toaster works in living room but not in kitchen...
all other appliances in kitchen works fine in all sockets...
toaster trips RCD in kitchen only...

Bruthal

sparkfireman wrote: »

if theres a neutral earth fault the RCD WILL trip with MCBs on!

If there is a neutral earth fault and nothing is plugged in on the circuits fed from the MCB`s then MCB`s on or off wont make a difference.

Bruthal

sparkfireman wrote: »

Ok...

Kitchen ring socket....
toaster works in living room but not in kitchen...
all other appliances in kitchen works fine in all sockets...
toaster trips RCD in kitchen only...

Did you take the socket off that the toaster is tripping in. and check it. Its a strange one

Bruthal

Anyway a megger is next, Switch off the RCD and the MCB for that circuit and test L to E and N to E with all appiances plugged out on the curcuit. If its clear then try same test with appliances plugged in.

M cebee

robbie7730 wrote: »

Anyway a megger is next, Switch off the RCD and the MCB for that circuit and test L to E and N to E with all appiances plugged out on the curcuit. If its clear then try same test with appliances plugged in.

250v between L-E and N-E

L+N bridged

if you're testing with appliances connected

Bruthal

M cebee wrote: »

250v between L-E and N-E

L+N bridged

if you're testing with appliances connected

Yes may as well bridge L-N anyway for the whole test. Id use the 1000v for the appliances plugged out test.

M cebee

sparkfireman wrote: »

Similiar off/on topic question.... Got a phone call just this minute and my head isnt right after an all nite house fire! :O

Jus outta bed...

But my mates immersion element keeps tripping RCD on BATH only...
His ma called an "electrician" friend of hers... who bypassed the RCD and immersion works fine on bath sink... etc....

How is this?? Is the whole tank live?

Cant think...

Someone answer

the immersion will heat partially

the main bond and cpc etc. will take the fault current

Bruthal

M cebee wrote: »

the immersion will heat partially

the main bond and cpc will take the fault current

Well depends on the fault, if the immersion element heating conductor is not broke it will still heat fully usually. But just as often it will be broke and only partially heat, i seen the outer copper split and the element part broke completely and the only circuit path was into the water and it still heated, partially.

M cebee

ya you're right it can be either scenario

Bruthal

M cebee wrote: »

ya you're right it can be either scenario

Bypassing the RCD is a bit nuts though is`t it.

M cebee

it's on a par with registered guys 'selling' certs in my book

Bruthal

M cebee wrote: »

it's on a par with registered guys 'selling' certs in my book

Are they selling them without doing the tests themselves?

SparKing

Well I'm not in favour of selling certs, but if the wiring is installed properly and the job is tested before certifying it then it's not unsafe, is it? So hardly in the same category as bypassing RCDs.
The Ecssa/Reci charge €300 or so to cert I believe, that is a big incentive to buy certs from contractors if you're wiring a house for a nixer.
At this stage I assume the OP has found the problem, what was up?

M cebee

ya right-:mad:

i don't mind being undercut by guys on the dole buying their certs off other contractors

and the sparkie doing the testing is going to enforce any neccessary remedial work-not likely!!

Bruthal

M cebee wrote: »

ya right-:mad:

i don't mind being undercut by guys on the dole buying their certs off other contractors

and the sparkie doing the testing is going to enforce any neccessary remedial work-not likely!!

Well it depends how its done, if a sparks rewires a house and then gets a contractor in who he knows well and they go through every test properly before he certify`s it, i dont see a big problem with that. Whats the difference between that and a contractor employing fellas to rewire some houses. Its not the same as a fella rewiring a house and a fella just sells him a cert without looking at the job.

Certs are only an indicator, not proof a job is done properly, and as a way of knowing who is responsible. If a shower was wired in 10 square but has connectors inside a partition wall, that would hardly be well within regs but would easily pass any tests.

Lots of sparks are on the dole, so should they not do any electrical job at all now? Lots of contractors dont enforce remedial work even on their own jobs or at least they do the quickest thing to get out of it. All the apartments and houses that went up in the big property boom had all sorts of rushed jobs done on them, i found one or two problems in my own house which im sure was certified by the contractor who did it.

If other contractors `sell`their certs without properly looking at and fully testing the job, then its them that are irresponsible more so than the sparks that bought the cert off them. Which was your point in the first place, but if the sparks supplying the cert does`t enforce any remedial work needed then he probably would`t on his own jobs which he has employees on. But just purely selling certs without looking at the job would be mad alright, like i asked before, is this done?

Bruthal

SparKing wrote: »

Well I'm not in favour of selling certs, but if the wiring is installed properly and the job is tested before certifying it then it's not unsafe, is it? So hardly in the same category as bypassing RCDs.
The Ecssa/Reci charge €300 or so to cert I believe, that is a big incentive to buy certs from contractors if you're wiring a house for a nixer.
At this stage I assume the OP has found the problem, what was up?

Well you have to differentiate between buying certs maybe, and getting a contractor to fully test the installation and certify on your behalf.
€300 may be a lot to get reci out to do a cert, but to get a major discount on that then the contractor would have to sell the cert without testing probably, because if he was to go in and fully test the job properly, how much would he charge to do the tests properly and certify. Would it be a lot less than the €300? Maybe it would.

M cebee

robbie7730 wrote: »

Well it depends how its done, if a sparks rewires a house and then gets a contractor in who he knows well and they go through every test properly before he certify`s it, i dont see a big problem with that. Whats the difference between that and a contractor employing fellas to rewire some houses. Its not the same as a fella rewiring a house and a fella just sells him a cert without looking at the job.

Certs are only an indicator, not proof a job is done properly, and as a way of knowing who is responsible. If a shower was wired in 10 square but has connectors inside a partition wall, that would hardly be well within regs but would easily pass any tests.

Lots of sparks are on the dole, so should they not do any electrical job at all now? Lots of contractors dont enforce remedial work even on their own jobs or at least they do the quickest thing to get out of it. All the apartments and houses that went up in the big property boom had all sorts of rushed jobs done on them, i found one or two problems in my own house which im sure was certified by the contractor who did it.

If other contractors `sell`their certs without properly looking at and fully testing the job, then its them that are irresponsible more so than the sparks that bought the cert off them. Which was your point in the first place, but if the sparks supplying the cert does`t enforce any remedial work needed then he probably would`t on his own jobs which he has employees on. But just purely selling certs without looking at the job would be mad alright, like i asked before, is this done?

i'm not concerned about the testing side of it-only the selling of the cert

to non-registered guys drawing the dole and working for 'cash only' that i have to compete against

-it's not a level playing field


i couldn't care less whether they get their houses tested or not:pac:

Bruthal

M cebee wrote: »

i'm not concerned about the testing side of it-only the selling of the cert

to non-registered guys drawing the dole and working for 'cash only' that i have to compete against

-it's not a level playing field


i couldn't care less whether they get their houses tested or not:pac:

True but very little in life is a level playing field, at some stage we could be the fellas on the other side of the inbalance.

Bruthal

Just as a matter of interest RCD problems such as this one are often caused my neutral earth shorts in the circuit somewhere. When there is a neutral earth short or fault after the RCD it can increase the live to earth fault current required to trip the RCD as now some of the earth fault current will end up going from the earth bar to the neutral earth short and back through the RCD. So if 10ma diverted this way it would take 40ma`s to trip the RCD L-E, as in it can increase the trip level to well over the 30ma live to earth current which is the type of current flow when a person contacts between live and earth which causes serious dangers.

Usually when there is a neutral earth short the RCD will trip when appliances are plugged into the affected circuit, and even sometimes when appliances used on other circuits especially heavy loads such as showers. But if nothing is being used it usually wont trip.

M cebee

the 30mA is providing protection against 'direct contact'

the n-e fault won't affect tripping normally on a path through the person to ground anyhow

does it affect it at all on a path back through exposed metalwork or pipework ?

Bruthal

M cebee wrote: »

the 30mA is providing protection against 'direct contact'

the n-e fault won't affect tripping normally on a path through the person to ground

only on a path back through exposed metalwork such as class1 applainces or pipework would it come into play

That may be, but its likely that fatal or dangerous shocks in the home will involve earthed metal work, as a person in dry conditions in the home could touch a 230v point and receive no shock at all if only in contact with the floor, its a certainty that if you contact 230v with shoes on and its dry there will be no perceivable shock unless your in contact with earthed metal. Some will believe that, some might not, but its certain.

Just about any shock we receive involves 2 points of contact besides the feet on the ground.

The other very dangerous one is working in wet conditions using 230v equipment where 110v should be used. But in the home its usually dry and the contact to the actual ground is minimal.

Bruthal

M cebee wrote: »

the 30mA is providing protection against 'direct contact'

the n-e fault won't affect tripping normally on a path through the person to ground anyhow

does it affect it at all on a path back through exposed metalwork or pipework ?

Its actually written somewhere in the regs about the neutral-earth short after the RCD affecting its operation, your certainly right about shocks to earth as in the ground,

When its back through pipework that is earthed to the earth bar it will have some affect, and any earthed metalwork especially when the only path back is to the earth bar rather than a pipe that goes into the ground as well. I would say myself the affect on the RCD is very small, but it is there alright.

But to say the 30ma RCD is providing protection against direct contact only is not entirely right, it will provide protection against any current which does not return on the neutral, so if you have a pipe in one hand and contact a live connection the RCD will trip immediately instead of leaving you exposed to live 230v. If you stand in the middle of the floor and contact 230v the RCD will not trip unless you have a very good contact with the earth.

I would`t recommend this obviously but i`ve tried it all, not all intentionally at times.

Its the reason in a TN system that everything must be cross bonded, so if the earthing becomes live then at least if its all at the same potential it reduces the chance of fatal shocks.

M cebee

i may not have thought the n-e fault situation through:)

anyhow on socket circuits the 30ma rcd is for personal protection-that is it's purpose