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advice on reason of tripping rcd


monkey5

Question

hi, first of all have had my phone off for about a week as it was damaged by son so was sent off to be repaired. turned it on last night about 8 and had 3 voice mails from a customer i had changed a consumer unit for about 3 weeks ago (having kitchen re decorated so wanted mire ways for there cooker and extra sockets). everything tested fine and had no tripping. the message was that the rcd has been tripping and could i call round asap. the first thing i did was panic as wasnt 100% how long it had been off for and felt bad because i hadnt contacted them back(phone off and being repaired so obviously i didnt know). so went straight round there last night and explained and apologised they seemed ok, turns out it had been off since sat after noon.first thing i did was ask if anything had been changed or done before it started to trip - no. they told me they had tried isolating each circuit and it still tripped whether they used a socket, or turned on the immersion or cooker. so i tried isolating (just to make sure) and still tripped. Faulty RCD? changed that and it still tripped. i noticed in the kitchen that the lights had been removed for decorating and the ends had been taped up, so i asked when this was done and turns out on friday night..... so removed the tape separated the cores and the tripping stopped. now when i removed the tape it did look like the cores were separated but i would had put more tape round each core to make sure there was no chance of anything touching that shouldnt be. i put it down to this.

then they asked well why it it take about 12 hours till it started to trip?

and why did it trip on other circuits even though the light circuit was isolated? (mcb switched off so neutrals and earth still connected).

How would you have answered these?

and what would charge as a call out charge for this? i did actually say dont worry about it as felt bad i hadnt known about it straight away but they did insist i charged them as it wasnt my fault and i had sorted it out for them. it took about an hour in all from my house to there (22miles round trip) fix the fault and get back home.

sorry for long winded explaination but wanted to give as much info as poss!Blushing

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It is likely that a neutral and earth cable were touching when they were taped. The reason RCD would trip even although lights MCB was off is because all circuit neutrals are connected together at the neutral bar in CU. Therefore any neutral shorting to earth effectively shorts all circuit neutrals to earth.

The time delay in RCD tripping would be dependant on the load being drawn from the CU. Would require 30mA imballance to trip RCD.

Charge either min 1 hour or whatever you charge for a call out.

basically what i thought and advised but wanted to double check, many thanks

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Neutral to earth fault definitely. Monkey, your story reminded me of some advice from an old sparks , always ask the questions first , such as , has any work been done recently, like picture hanging, plumbing , DIY , builder, any new lights fitted. Amazing how many people don't offer any info, think you are a magician.

Same with machine breakdowns, grab the operator if possible, he says something like Oh it was fine till I pressed this button and there was a bang from that box , now you are halfway there .

Deke

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Neutral to earth fault definitely. Monkey, your story reminded me of some advice from an old sparks , always ask the questions first , such as , has any work been done recently, like picture hanging, plumbing , DIY , builder, any new lights fitted. Amazing how many people don't offer any info, think you are a magician.

Same with machine breakdowns, grab the operator if possible, he says something like Oh it was fine till I pressed this button and there was a bang from that box , now you are halfway there .

Deke

thanks evans, i did actually ask first off but as it didnt start tripping as soon as there lights were taken down they didnt think it was that - sure it wont be the first time!. next time ill make sure and ask anything changed anytime before fault whether straight before or the day before or the week before etc.

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It is likely that a neutral and earth cable were touching when they were taped. The reason RCD would trip even although lights MCB was off is because all circuit neutrals are connected together at the neutral bar in CU. Therefore any neutral shorting to earth effectively shorts all circuit neutrals to earth.

The time delay in RCD tripping would be dependant on the load being drawn from the CU. Would require 30mA imballance to trip RCD.

Charge either min 1 hour or whatever you charge for a call out.

Hello Rack Failure welcome to the forum. Your user name is very unusual and has got me thinking as to what it may relate too.

Batty

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I had something like this about a year ago..

I'd been in doing some work (bathroom fan if I remember) and as part of installed a RCD for the circuit (lights).. I get a call from the plumber who I subbed the work for saying that his customer was irate..

Now I'd had 2 pints, so I got the wife to drive me up there with a few tools and the fella was absolutely bouncing (& ****ed) saying he was going to sue me, etc.. etc....

We (& his wife) eventually calmed him down and asked him if he'd done any nailing, screwing or drilling; and he said he'd just boxed in some pipes... it wasn't that so we asked if there was anything else and he admitted he'd nailed down some floor boards,,,,, straight through the middle - not even at the edge!!

Luckily for him he still owed me some money from the job, otherwise I'd have told him where to go..

Oh yeh,,, that ended up being an expensive nail!

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Hello Rack Failure welcome to the forum. Your user name is very unusual and has got me thinking as to what it may relate too.

Batty

Hi Batty

I used to be a contracting spark many years ago, now a maintenance spark for over 30 years. Part of my work involves working with Siemens' PLCs, Simatic Step 7 etc. In the early days we used to have the processors going into stop mode with error 'OB86 Rack Failure'. The Rack Failure part has always stuck in my mind and I use it for a user name in other forums too.

PS Although I've only recently joined (found) this forum I am quite impressed with it and the postings. I can also be found lurking in the DIYNOT forums, there good too.

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PS Although I've only recently joined (found) this forum I am quite impressed with it and the postings. I can also be found lurking in the GRANNYKNOT forums, there good too.

don't mention the other's. shh.

we are be best and the nicest and the friendliest!

:D

Go and introduce yourself and we can all say hi

here

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RCD's can be buggers. I almost always warn customers before DB changes (particularly in older properties) that they may experience some nuisance tripping. You change an ancient rewirable fusebox to an RCD consumer unit and the RCD will trip for earth faults in the wiring, or in equipment that older fuses would not pick up.

I had a very similar experience a few years ago where the house had no earth whatsoever and an ancient rewirable fusebox. I drove in an earth rod, installed the new box then went on holiday for a week. I came back to a very irate customer and, like yourself went straight round there. I asked her what she had been doing.

"I was doing the washing"

"Can I see the washing machine?"

About a thousand year old integrated washing machine, switched off washing machine: no trip.

Switched on washing machine: trip

Washing machine's goosed, get a new one!

It actually degenerated into the "well it was fine before you changed the box" conversation... Naw it wiznae! Yer hoose had nae earth and an antiquated protection system. Sleep well, you won't burn in yer bed the night!!

You'll never tell some of them!

Get yer excuses in early!!

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That is the classic when you fit an RCD , "this never happened before you changed it."

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Hi Batty

I used to be a contracting spark many years ago, now a maintenance spark for over 30 years. Part of my work involves working with Siemens' PLCs, Simatic Step 7 etc. In the early days we used to have the processors going into stop mode with error 'OB86 Rack Failure'. The Rack Failure part has always stuck in my mind and I use it for a user name in other forums too.

PS Although I've only recently joined (found) this forum I am quite impressed with it and the postings. I can also be found lurking in the DIYNOT forums, there good too.

Well I would never have guessed that welcome anyway.

Batty

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It is likely that a neutral and earth cable were touching when they were taped. The reason RCD would trip even although lights MCB was off is because all circuit neutrals are connected together at the neutral bar in CU. Therefore any neutral shorting to earth effectively shorts all circuit neutrals to earth.

The time delay in RCD tripping would be dependant on the load being drawn from the CU. Would require 30mA imballance to trip RCD.

Charge either min 1 hour or whatever you charge for a call out.

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RCDs are sensitive - as RF said above - It could be a Neutral-Earth.

I remember isolating and cutting through a cable, Way before I trained as a spark.

Result - RCD tripped. Even though the circuit was Isolated.

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Neutral to earth connected together under the tape

Why not ask for

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