Rcd

[dave1064]

Tested all circuits All test out perfectly. Found fault. Due to a blown transformer in a elv fan. RCD picking it up where testing did not.

 

[trev]

Surely your IR test would have shown trannys in the circuits? Or did you just whack 500v through them?

 

[davethsparky]

What exactly had gone wrong with it? I am amazed that the full testing process failed to pick this up.

 

[Darkwood]

Tested all circuits All test out perfectly. Found fault. Due to a blown transformer in a elv fan. RCD picking it up where testing did not.

Assuming the fan is in the bathroom if the RCD can see the fault then this would have picked up straight away by functional testing ..going around switching everything off and resetting then each item on one at a time... had you missed that the transformer has obviously got an earth fault which will have been picked up with an insulation test unless you hadn't had the fan switch on when testing ..but 2 crucial tests will have identified this issue...

 

[davethsparky]

Maybe not so easy on functional test, if the fault was neutral to earth and the fan was on its own separate switch for instance. But IR test for sure

 

[Darkwood]

Maybe not so easy on functional test, if the fault was neutral to earth and the fan was on its own separate switch for instance. But IR test for sure

Good point but dropping out each circuit from the dist board even before testing would have given big clues and would have expected to have done all the options above as an electrician before even contemplating posting a thread on it... in doing so it shows a lack of competence IMHO.

 

[brightspark2010]

check all circuit neutrals are in there coreesponding rcd neutral bars anything under load in wrong neutral bar will obviously trip its rcd instantaneously other than that as stated get testing properly you will find the problem soon enough with logical procedures

 

[mayfair]

Had ONE this year and a couple last year as for the rest of the 100's guess what a fault elsewhere

Why do so many people just assume that an rcd or mcb must be faulty if it trips? Why not assume its doing its job and operating due to a fault?

I'm interested to know how many faulty rcd's people on here have found?

 

[davethsparky]

Good point but dropping out each circuit from the dist board even before testing would have given big clues and would have expected to have done all the options above as an electrician before even contemplating posting a thread on it... in doing so it shows a lack of competence IMHO.

But that's a procedure that doesn't figure in the course notes of the proprietary course in domestic bodgery and scarpering, how on earth would anyone know to do that? Next you'll be expecting people to understand what these magical trippy thingys we put in fuseboards actually do.

 

[trev]

Just as a moment of levity.
I went for a pint on my way home today as I needed to have a word with someone who I knew would be in the pub, while chatting another guy joined in and asked what I did, when I told him he said there was one question which had always bugged him. This was it word for word.
"When you have a short circuit the electricity runs away and doesn't power anything, how does it know which wire to run back up to trip the trip thing"
I know I shouldn't have but I really wanted to laugh at him.

- - - Updated - - -

I gave him a very brief, laymans explanation though.

 

[dazza1981]

Was he a sparks trev??? lol

 

[trev]

Thankfully no mate, solicitor but I did ask if he was a Electrical Trainee

 

[Guitarist]

Tested all circuits All test out perfectly. Found fault. Due to a blown transformer in a elv fan. RCD picking it up where testing did not.

I take it that you disconnected the tranny for testing then?

 

[GLENNSPARK]

Tested all circuits All test out perfectly. Found fault. Due to a blown transformer in a elv fan. RCD picking it up where testing did not.

jesus wept...

 

[GLENNSPARK]

I have a couple from this year in a box of failed parts I keep for interest - one has the N contacts that most times don't quite close, and one that is almost jammed and will only trip maybe 1 out of 10 times when tested. I'd say a faulty RCD is more likely to not trip when it should, than trip when it shouldn't. Again, far more faulty circuits than faulty RCDs.

nah...
more than likely it wont hold...

 

[SJD]

nah...
more than likely it wont hold...

OK, yes - I suppose I sort of contradicted myself with my example anyway.