ProDave Problem, Lamp becomes live when CU switched Off!

[Sidewinder]

Locked off I hope lol ---------- Post Auto-Merged at 14:16 ---------- Previous post was made at 14:15 ----------

And I remember this too so I'll keep out of it

---------- Post Auto-Merged at 14:17 ---------- Previous post was made at 14:16 ----------

Sidewinder likes cutting next doors cables in adjoining lofts

You can go off some people, especially when they have been searching the forum!...

 

[gavindrummond]

Was it a temp supply whilst the house was in the midst of being built and when everything got installed the temp was not disconnected?

 

[ProDave]

Was it a temp supply whilst the house was in the midst of being built and when everything got installed the temp was not disconnected?

No.

It was just a simple mistake in the wiring somewhere that went unnoticed by whoever did the inspection and testing. Just the one normal supply into the house.

 

[Guy]

bad day explode

 

[Doc Hudson]

Posts moved onto a new thread from the original Problem of the week thread. this should make it easier for others to find the beginning of a problem and comment or ask further questions about an earlier problem.

Doc H.

 

[ProDave]

Just to say I'm off out today, so if I don't get the chance to answer more questions until this evening, it's because I'm not here.

 

[ProDave]

So has anybody got any more questions, any more checks or inspections to do to work out the fault?

Or do you want to post the solution?

 

[gavindrummond]

So originally you where there to fix a damaged 3core&e lighting cable. You were going to terminated it into a junction box and cable clip to avoid any further issues, but your lead lamp was plugged into a socket on the landing??? And when you decided to cut through the damaged cable the the lead lamp suddenly came on. It's the the socket that's the fault is with and not the 3 core & earth?

 

[springcrocus]

Did the original installer dismantle the board to facilitate mounting?

 

[ProDave]

Strictly speaking the "fault" was not with either final circuit.

You are on the right lines about the board possibly being dismantled. In which case was it re assembled correctly?

If YOU had encountered this, i.e the main switch was off, but suddenly starting to cut through a cable powered up the socket the lead lamp was plugged in to, where would you go and look first to take some readings?

 

[gavindrummond]

I'm going to have to leave this dave as I have never come across this. I've never actually done any fault finding. But will follow to see what happens

 

[springcrocus]

Strictly speaking the "fault" was not with either final circuit.You are on the right lines about the board possibly being dismantled. In which case was it re assembled correctly?

If YOU had encountered this, i.e the main switch was off, but suddenly starting to cut through a cable powered up the socket the lead lamp was plugged in to, where would you go and look first to take some readings?

I posted the way I did because, if what I think has happened is correct, I didn't wan't to spoil the fun for others trying to solve this. I, too, have "tidied up" after another spark has done his work. Just the one RCD, was there?

 

[lineman]

Is this in student area as can't see on iPhone or can anyone have a go?

 

[NozSpark]

It is in the student area Lineman, I PM'd Dave my guess to let others have a go,

It is both an obvious and obscure "fault"

 

[lineman]

Roger that!

 

[ProDave]

I'll give you another prompt to try and get you thinking.

The main switch is turned off, so you would expect the whole house to be dead, but clearly it's not.

so might a good place to start be remove the cover from the CU and have a look at that main switch and how it's wired?

What would you like me to look for and what tests would you like me to do?

 

[Guy]

can I assume that it is a double pole isolator?

 

[sammers230]

Is it if they dismantled the board, upon reassembly they have put the tails from the RCD on the incoming side of the main switch allowing the RCD side of the board to remain live? Just a bit of a stab, but as most domestic electrics go as far as I have seen anything is possible in the world of mess ups

 

[ProDave]

Very nearly sammers

If the tails from the RCD side went to the main switch incommer, then the sockets would not have turned off when I turned the main switch off.

So think about it a bit more. How was it possible that the sockets turned off when the main switch was turned off, but came on later as I went to cut the damaged wire?

 

[sammers230]

I would say loose terminals inside the board and a faulty main switch but you already mentioned about the switch was still off (unless was a faulty switch) allowing the RCD tails to stay touching but the bus bar for the non RCD side falling out. When you light came back on was the cable to be repaired live again?