Intermittent electrical fault

Bruthal

THENORTHSIDER wrote: »

possible that you may be inheriting fault from outside your board. Your neighbour isn't doing any type of commercial work in his shed

Whats the theory on this one?

THENORTHSIDER

This theory of the loose connection (seeing as you are on about theories) it would have to be very loose , as there would have to be absolutely no contact between the cable and the terminal to create an open circuit.A core simply resting on a terminal will allow current flow. Secondly If an installation had an inadequate eathing system ,an earth fault will take the path of least resistance. Welders can also create earth problems. Is that a suitable answer for you:cool::cool: Will head to the college Library Monday for the referances no doubt you will require

Bruthal

THENORTHSIDER wrote: »

If an installation had an inadequate eathing system ,an earth fault will take the path of least resistance. Welders can also create earth problems. Is that a suitable answer for you:cool::cool:

An earth fault may not take only the lowest impedence path, but any paths available.

Its unlikely next doors installation is causing the problems here. They used to years ago on voltage operated ELCB`s, but to happen now is unlikely, but marginally possible on a row of houses with small overhead lines and a heavy load on one or more houses, but it would still need a neutral-earth fault in the installation thats tripping the RCD now. Usually TN-CS eliminates this.

As for the path of least resistance, when you turn on a shower (6 ohms) and a 60w bulb (880 ohms), which one is the path of least resistance? And which path does the current take? Not just the least resistance path anyway.
Most will take the lower impedence path alright, but it still takes any open to it.

THENORTHSIDER

robbie7730 wrote: »

An earth fault may not take only the lowest impedence path, but any paths available.



As for the path of least resistance, when you turn on a shower (6 ohms) and a 60w bulb (880 ohms), which one is the path of least resistance? And which path does the current take? Not just the least resistance path anyway.
Most will take the lower impedence path alright, but it still takes any open to it.

this isn't a fault situation so irrelavent:cool::cool:

Bruthal

THENORTHSIDER wrote: »

This theory of the loose connection (seeing as you are on about theories) it would have to be very loose , as there would have to be absolutely no contact between the cable and the terminal to create an open circuit.A core simply resting on a terminal will allow current flow. Secondly If an installation had an inadequate eathing system ,an earth fault will take the path of least resistance. Welders can also create earth problems. Is that a suitable answer for you:cool::cool: Will head to the college Library Monday for the referances no doubt you will require

No theories, loose connections often cause intermittent on-off problems in circuits. You dont believe thats possble, fair enough. But any competent sparks would clearly know that without library visits.

The OP`s problem is sockets sometimes went off, and came back on themselves. And also sometimes the RCD tripped. Changing the RCD may fix it, as it may be faulty and have bad contacts, or there could be both an earth fault within the installation, and a loose connection in the DB.

Or too many circuits on that single RCD could be causing its tripping problems. Small leakages add up on each circuit downstream of an RCD.

But if you can rule out loose connections causing the on-off part of the problem, on the basis that all a connection needs to be sound is to be touching, then the library might well be a good place to go.

Once that phrase "current takes the path of least resistance" is mentioned, that usually says a lot, as its a phrase heard and then regurgitated without actually thinking about it. And it still didn`t explain how the neighbour using a welder would cause the problems in this thread, even with that sunglasses face thing. Strange things happen in electrical, but that would be an interesting one.

I have actually seen an RCD tripping in a house with the main switch off, but this house still had a neutral directly connected to earth in a socket, so enough current was diverting from the overhead neutral outside, in through the RCD, and to the earth wire at the neutral earth short, and onto the earth bar to earth rod. The house was not neutralised. If it had been, this probably would not have happened. But even as it was, the house in question still had an earth fault causing the tripping, which once removed, was fine. In this case, the load from other houses was contributing to the tripping. Mainly because of the small undersized overhead lines outside the houses.

Bruthal

THENORTHSIDER wrote: »

this isn't a fault situation so irrelavent:cool::cool:

Your making no sense now.

Bruthal

THENORTHSIDER wrote: »

possible that you may be inheriting fault from outside your board.

THENORTHSIDER wrote: »

this isn't a fault situation so irrelavent:cool::cool:

I see:rolleyes:

THENORTHSIDER

robbie7730 wrote: »

An earth fault may not take only the lowest impedence path, but any paths available.



As for the path of least resistance, when you turn on a shower (6 ohms) and a 60w bulb (880 ohms), which one is the path of least resistance? And which path does the current take? Not just the least resistance path anyway.
Most will take the lower impedence path alright, but it still takes any open to it.

Irrelavent as this isn't a fault situation. Whilst I think we have gone way off the problem here its ok to say a TN-C system USUALLY eliminates this but has the OP stated what type of supply he has

Bruthal

Maybe you meant my item about the shower and the bulb was not a fault situation so its irrevelent. But its not really. A fault current flows through all paths open to it, not just the lowest impedence one.

But you said that in refererence to saying next door might have been causing it. So, explain how a fault next door would trip an RCD in the Op`s house here. Exactly how it would happen, not just that phrase, about fault current taking the path of least resistance as an explanation.

Bruthal

THENORTHSIDER wrote: »

Irrelavent as this isn't a fault situation. Whilst I think we have gone way off the problem here its ok to say a TN-C system USUALLY eliminates this but has the OP stated what type of supply he has

Makes no difference what setup he has really with reference to a fault next door. The OP`s RCD is unlikely to trip if there are no faults in his own installation downstream of the RCD. My mention of the neutralised setup was to show current can be diverted into a fault downstream of the RCD. But it was not diverting fault current in, just the normal neutral current on the overhead line outside. How can earth fault current next door cause the RCD to trip in this case here if this installation has no fault?


In reality, the problem in this situation may well be a double fault. This RCD has too many circuits on it in my opinion, and it was another 2 fellas mentioned that earlier in the thread also, and i would listen to their opinions. So it may well be tripping due to accumulation of small leakages.

But the sockets going off and back on themselves is also happening. How is that?

Bruthal

Anyway, if we are gone away from the problem, here it is.

Sockets go off and back on themselves sometimes.

RCD sometimes trips.

So, faulty RCD possible, with bad contact(s) in it too.

Neutral earth fault in a socket circuit tripping the RCD, and also a loose connection causing the intermittent on/off of socket circuits. Possibly even a live earth problem, but that would usually trip the MCB also.

Or too many circuits on a single RCD, causing accumulated leakages combining enough to trip the RCD depending on whats running at any time, and a loose/bad connection.

You seem to rule out loose connection NORTHSIDER. But i would think it possible, simply because its obviously a possibility.

The RCD maybe getting replaced will fix all problems, and make it look like the loose or bad contact/connection was not part of it.

But i cant think of many causes for circuits going on and off and back on themselves beisdes connection or bad contact problems. Maybe you can?

THENORTHSIDER

Any developments

M cebee

i was waiting on you

to come back from the library with the solution

Bruthal

M cebee wrote: »

i was waiting on you

to come back from the library with the solution

Blowheads

Hi all, many thanks for replies. Intermittent fault still occuring, last night at 3am so could really rule out the neighbour welding! Could anyone recommend a sparks on galway that could cure this?

Blowheads

Hi all, many thanks for replies. Intermittent fault still occuring, last night at 3am so could really rule out the neighbour welding! Could anyone recommend a sparks on galway that could cure this?

THENORTHSIDER

not related to my welding neighbour then.

Am waiting for the return of 'Electrical Principles' in the Library :rolleyes: :rolleyes: :rolleyes:

Bruthal

Well im a carpenter but have worked around sparks a lot, ye pick up a few things about it along the way.

Blowheads

just one to close this off.

Strange as it seems we replaced the iron and the issue disappeared. I didnt understand how when it is switched off but still plugged in it could be causing this issue

Irish Steve

If it's a steam iron, a minor leak from the water tank running down on to internal connections could have produced a neutral to earth short, which will take out the trip even if there's no power on the circuit. Seen similar happen before when neutral and earth touch when replacing a faulty socket, even though the RCB is off on the circuit, the trip is doing the job it's there for.

Bruthal

Irish Steve wrote: »

If it's a steam iron, a minor leak from the water tank running down on to internal connections could have produced a neutral to earth short, which will take out the trip even if there's no power on the circuit. Seen similar happen before when neutral and earth touch when replacing a faulty socket, even though the RCB is off on the circuit, the trip is doing the job it's there for.

Water from neutral to earth wouldnt usually make a good enough connection to trip the RCD when that circuit MCB is off, unlike a direct neutral to earth short. It would be more likely there is an actual intermittent direct neutral earth fault in it.

Irish Steve

Bruthal wrote: »

Water from neutral to earth wouldnt usually make a good enough connection to trip the RCD when that circuit MCB is off, unlike a direct neutral to earth short. It would be more likely there is an actual intermittent direct neutral earth fault in it.

Fair comment, I was more thinking in terms of making the point that a neutral to earth fault can happen when the item is off, but plugged in.

Many years ago, had a similar fault with water that had a high lime content getting into the back of a socket, running down the cable, and that was intermittently throwing the trip out, even though nothing was plugged in to it. Turned out the spark had nicked the neutral insulation when cutting back the outer PVC with a Stanley knife.

2 fixes, a piece of heat shrink on the neutral line, and find and stop the water, which turned out to be condensation running off a window cill from a large single glazed window above the socket, which was mounted in a box sunk into an internal natural stone decorative wall, so the water was not clean as such. Took some finding, as it was intermittent.

Not a job I repaired, but had a restaurant here in Ashbourne a couple of weeks ago where rainwater came over the end of a gutter, and got into the building, ran down the wall a little, and then dripped on to the outside of a 4 core 25 mm SWA cable, ran down that, got round the gland in the top of the MCB box, and then dripped on to the 3 phase bus bars under the MCB's. Took out all 3 of the 63A fuses in the Landlord fuse box, as someone (NOT ME) had put 80A fuses in the board.

Pain, as the landlord box wasn't accessible until the next morning, so had to run extension leads all over the place from areas that were still live to keep fridges and freezers going.

Dotsie~tmp

I recently had an intermittent earth fault that took 4 months to track down. Useless clients that never absorbed the basic RCD fault routine. A DIY electriic house with a dozen red herrings. Never called me when the fault was active, always a day later but only found out after driving down, even after asked was it no longer present. Got lucky one day the daughter called as the fault happened and was able to track it to the freezer while active.

Many visits and never had the heart to charge em fully for the whole saga. Always feel word of mouth and karma rewards when .a decent bit of work arrives on these. Probably why im poor.