Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: TD on 04 February 2017, 18:09:07
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I have a fault with the kitchen/bedroom circuit...
Basically a short circuit between neutral and earth (as measured by my multimeter)
So I thought I would try to find out where the problem was....I was thinking it was going to be in the loft above the kitchen, where I get occasional furry visitors who like to chew cables.
After a bit of diagnostics....ie breaking the circuit...I identified which cable had the problem...
So up into the loft ...... and cut the cable I thought was the problem about 6 inches from where it enters the loft from the main house....stripped it back (the cable from the house) and opps me its still got a short :( Obviously changed the cable as I had to now.
Ive broken the circuit upstairs and now all the kitchen sockets are good apart from the one I changed the cable.
So, to my thinking the fault must lie in one of the bedrooms....which is a buggar.....coz it means clearing rooms and floor boards up :(
Unless any of you clever chaps can think of another reason for the short....I did think there maybe a problem with the circuit breaker...but as it only switches the 'live' I had my doubts.....
The only other thing I can add is when the fault developed I had left an iron turned on in one of the bedrooms.....ummm for about 24 hours....but seeing as the iron still works....I carnt see it causing the fault :-\
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You've got Leccie? :o
Lucky you :(
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Have you had a look at all the sockets in the bedroom to make sure it's not at the back of one of them?
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Have you had a look at all the sockets in the bedroom to make sure it's not at the back of one of them?
As highlighted
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Just check everything is unplugged from the sockets then test again , if that doesn't help turn the power off and start disconnecting the sockets one by one testing every time to see if the fault clears (leave them disconnected ) check the socket as well just in case that is the problem and move to the next one . Hopefully you will find something or at least narrow it down
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Just what problems/difficulties does this Eart-to-Neutral short cause you?
Ron.
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If its a ring circuit go to the fuseboard and disconnect 1 leg and remove a socket/split wires,then power it up.If it works great then see how many sockets have electric and which don't,i would use a kettle or the iron because your testing the neutral /earth also.A process of elimination should narrow it down to 2 sockets and the offending cable.As mentioned earlier be sure there is nothing still plugged in as that could be the faulty item.Is the system covered by an rcd/main switch?
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daft question but has everything been unplugged on the circuit - absolutely everything in the bedrooms as well?
I think you can discount the rcd as that does not have any connection to the earth.
best to pop each faceplate off in turn in the bedrooms and test. At least you'll identify ifi t is one of those or which wiring leg. Givne you have a multimeter, I'd dead test rather than live
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Have you had a look at all the sockets in the bedroom to make sure it's not at the back of one of them?
No, not yet
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Just check everything is unplugged from the sockets then test again , if that doesn't help turn the power off and start disconnecting the sockets one by one testing every time to see if the fault clears (leave them disconnected ) check the socket as well just in case that is the problem and move to the next one . Hopefully you will find something or at least narrow it down
Everything is unplugged....and the power isn't on as it trips the main breaker if I try to turn that circuit breaker on
I will try your suggestion of disconnecting all the bedroom sockets, as I should find which socket or run of cable that is causing the problem :y
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Just what problems/difficulties does this Eart-to-Neutral short cause you?
Ron.
It trips the main breaker....
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What type of main switch do you have on your fuse board?
A neutral to earth fault won't trip an ordinary circuit breaker but the same fault will trip an RCD or an RCBO (RCBO is an RCD with overload protection combined)
Does the breaker that trips have a test button on it ?
Any chance of a picture of the board?
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What type of main switch do you have on your fuse board?
A neutral to earth fault won't trip an ordinary circuit breaker but the same fault will trip an RCD or an RCBO (RCBO is an RCD with overload protection combined)
Does the breaker that trips have a test button on it ?
Any chance of a picture of the board?
To all intents and purposes, neutral is earth.
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What type of main switch do you have on your fuse board?
A neutral to earth fault won't trip an ordinary circuit breaker but the same fault will trip an RCD or an RCBO (RCBO is an RCD with overload protection combined)
Does the breaker that trips have a test button on it ?
Any chance of a picture of the board?
The main breaker for all power is a 60amp with earth leakage trip with a test button.
The breaker for the circuit that's not working is an ordinary 30amp trip with no earth leakage on it.
Its when I try to turn on the breaker for the circuit, this stays on but the main breaker trips.
Ive got a bit further with this now ..... I took all the socket of upstairs and disconnected their neutrals
Measuring them with a meter, I found a neutral/earth short on a wire in 2 of the sockets, so I assume that this wire links the 2 sockets together. So I reconnected the sockets leaving these two neutral wires disconnected.
However the main breaker still kept tripping when I turned on the breaker for the circuit.
So I decided that maybe the live had a problem between these two sockets as well, so I disconnected the live from these 2 sockets as well. So that just leaves one live/neutral/earth going to these two sockets.
The main circuit breaker now stays in when I turn on the breaker for the circuit.
Now this is where is confuses me, because none of the sockets work anywhere on the circuit, id expected some if not all of them to work ???
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If you have a combined RCD / main switch, disconnect ALL neutrals from the bus bar at the back of the consumer unit.
Turn off ALL circuit breakers.
Re connect 1 neutral circuit / switch on that circuit breaker then start again.
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Yes, STEMO, that is why I asked my earlier question. In most (all?) installations, the neutral feed is connected to earth at its entry point to the property. As such, I couldn't see why an E-to-N short circuit would cause a problem. ???
Ron.
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To all intents and purposes, neutral is earth.
It might be at the same potential normally, but it's very different, and this also depends on the type of earth the incoming connection to the property is provided with.
I would disconnect both legs of the circuit at the consumer unit, and go round every socket separating the two legs and testing for the short. Fairly soon you'll find the faulty section of cable or (more likely) find a wiring fault behind a socket.
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What type of main switch do you have on your fuse board?
A neutral to earth fault won't trip an ordinary circuit breaker but the same fault will trip an RCD or an RCBO (RCBO is an RCD with overload protection combined)
Does the breaker that trips have a test button on it ?
Any chance of a picture of the board?
To all intents and purposes, neutral is earth.
Not to an R.C.D.
Neutral should be at earth potential but is not always the case
https://en.wikipedia.org/wiki/Residual-current_device
Hopefully this offers an explanation of how an R.C.D. works
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Yes, STEMO, that is why I asked my earlier question. In most (all?) installations, the neutral feed is connected to earth at its entry point to the property. As such, I couldn't see why an E-to-N short circuit would cause a problem. ???
Ron.
In a TN-S system which provides separate earth and neutral at the consumers premises (the earth and neutral are joined together at the supply transformer, this is a very common type of supply in the U.K.
In a TN-C-S (aka PME) system the earth and neutral and earth are joined together at several points between the supply transformer and the consumers premises but are separated at the cable head where it comes into the premises.
TN-C & TT systems are also used by supply authorities.
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Yes, STEMO, that is why I asked my earlier question. In most (all?) installations, the neutral feed is connected to earth at its entry point to the property. As such, I couldn't see why an E-to-N short circuit would cause a problem. ???
Ron.
Apparently, we're old school, Ron. :(
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But......still don't see how an E/N short would cause the main circuit breaker to go, even though it might trip an RCD.
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You learn something new every day, "Ever Ready"!
Way back in my youth (ahem, a few years ago...) I learned that there could be a potential between earth and neutral some distance from the supply point, so I took great delight in getting "free" electricity by connecting a torch bulb between them in my bedroom - and it worked! 8) 8) 8)
Ron.
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You learn something new every day, "Ever Ready"!
Way back in my youth (ahem, a few years ago...) I learned that there could be a potential between earth and neutral some distance from the supply point, so I took great delight in getting "free" electricity by connecting a torch bulb between them in my bedroom - and it worked! 8) 8) 8)
Ron.
Good job the PD wasn't much, Ron, or you'd have made a loud 'POP!'
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But......still don't see how an E/N short would cause the main circuit breaker to go, even though it might trip an RCD.
main circuit breaker has the RCD built into it, in my case :y
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Every day is a school day even for old dogs like me :y :y
Back when I started my apprenticeship in the seventies we never had circuit breakers never mind pesky RCD's
Everybody used to keep a card of fuse wire, usually from Woolies :) to rewire their fuses.
I was talking to a young pup (45) on site yesterday who can't remember a time before MCB's :o
Having an RCD as your main switch ( a requirement if your method of supply is aTT system) creates problems when one circuit causes a fault and puts the whole house in darkness.
One answer was split load boards with some circuits on the RCD and others not.
The best solution in my opinion is individual RCBO's which provide RCD protection and over current protection. Can be seen as too expensive
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To all intents and purposes, neutral is earth.
It might be at the same potential normally, but it's very different, and this also depends on the type of earth the incoming connection to the property is provided with.
I would disconnect both legs of the circuit at the consumer unit, and go round every socket separating the two legs and testing for the short. Fairly soon you'll find the faulty section of cable or (more likely) find a wiring fault behind a socket.
I think I'm going to have to do that.....
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Before you do that TD have you got any fused spurs connected to the circuits?
Burglar alarm panels etc are often spurred off the ring main.
Just a thought before you start dismantling your house :) :)
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Before you do that TD have you got any fused spurs connected to the circuits?
Burglar alarm panels etc are often spurred off the ring main.
Just a thought before you start dismantling your house :) :)
Good thinking :y
But the only fused spur went to the boiler.....which I have ripped out the cable and shoved a plug on the end and plugged it into an extension lead running from the dining room....so I have heat and hot water :)
Fridge/freezer is plugged into socket on the cooker panel and I have another extension lead for the other appliances in the kitchen....bit of a pain as I can only use one appliance at any time, so as not to overload the extension cable...but liveable with for the time being.
I haven't done anything on it this afternoon as I went over to my mums....I'm going to leave it until I can spend a day on it :y
I'm still wondering if leaving a steam iron for 24hours could have caused the fault :-\ as the socket in the bedroom where it was plugged in was where I found the original N/E short.....then got very confused as to what was going on.....
Hence I think Mr Woods suggestion is the way forward...
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Decided to have a go at the problem again this morning...
So did as Kev suggested.....disconnected L/N tails from the consumer unit and went round checking at the sockets (I had all the sockets disconnected too)
The N/E short (0.2 ohm) I was seeing yesterday had disappeared....I even checked at the consumer unit....no short. I also checked the sockets....
So reconnected all the sockets but left them hanging.....checked at the consumer unit....no short
Reconnected the tails at the consumer unit and turned the power back on......circuit working again, power at all the sockets.
Leaving the power on I reattached the sockets....half expecting the power to trip once the wires were pushed back in the back boxes.
But no, power stayed on.
So don't you just hate it when that happens. Fault has magically disappeared! Disturbing the wiring seems to have done something :-\ :-\
Gonna pop out to screwfix now and get one of these just to double check the sockets are ok....
http://www.screwfix.com/p/lap-ms6860d-socket-tester/91596?_requestid=136864
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Got the above tester and checked all the sockets.....all ok L/N/E present all the sockets :y....altho the tester carnt check a N/E reversal... but I'm not that much of an idiot to get that wrong.....been ok for about 8 hours now....
I'll give it a few days, to make sure the fault has disappeared......then reconnect the boiler to the fused spur...
Happy bunny at the moment..... :)
Thanks to all who suggested the way forward :y
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Glad to hear you are up and running again, Sods law the fault will return at the most inopportune moment, My next step would be to carry out an insulation resistance test but I know that not everyone has access to more specialist test equipment.
I have lost count of the number of testers I have bought and tested over the years. Some are even analogue :o :o
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With my technique you would saved a lot of time and had some electric and found the fault.....