Rcd advice needed faulty or fault

[Stuportsmouth]

So had to fit a new shower as old one kept tripping the rcd after few seconds assumed the shower was to fault as made a buzzing noise and tripped, on fitting the new shower it had same faukt so checked pressure of water no issue then checked wiring at box also no issue so moved onto next possibiliy of short on cable.
Yes maybe should of used multimeter and tested each one out but easier as short run in walls so run new cable exactly the same.
So decided to wire a small flex with bulb holder on that trips rcd changed the 40amp mcb to a 16 amp tried light also trips could this be a faulty rcd its rated 80amp 30ma, we also tested the the curcuit with every mcb turned off with only shower circuit on and also tripped.

Any help would be greatly appreciated as would like to think in a 6 bedroom house with each room occupied that of rcd was faulty then it would trip as currently has approx 8 circuits on and only randomly started to happen nothing new has been added.

 

[Octopus]

Where is the circuit for the shower? What rating is the MCB?

Strikes me that without proper test kit and the knowledge to use it and interpret the results you may well be wasting your time ....

 

[Stuportsmouth]

Where is the circuit for the shower? What rating is the MCB?

Strikes me that without proper test kit and the knowledge to use it and interpret the results you may well be wasting your time ....

40amp mcb and mcb is also not tripping used the spare 16amp with lightbulb circuit and still done same a ramp test could be beneficial to test the rcd but then changing the rcd of possibly faulty is also easy main thing being tho of the rcd is faulty it would trip with all the other circuits on board under load and would assume with then isolated that if there was a fault on a circuit with all mcbs turned off that would isolate any fault.
Shower is currently not on any circuit as removed from box and left isolated outside of fuse box

 

[Octopus]

40amp mcb and mcb is also not tripping used the spare 16amp with lightbulb circuit and still done same a ramp test could be beneficial to test the rcd but then changing the rcd of possibly faulty is also easy main thing being tho of the rcd is faulty it would trip with all the other circuits on board under load and would assume with then isolated that if there was a fault on a circuit with all mcbs turned off that would isolate any fault

Punctuation would help!

using what?

regarding isolation of circuits using MCB's, best you ask your dad about how RCD's work ....

 

[123]

What concerns me here is everything is going to be tried until the shower works and nothing trips...and then its going to be left at that as it works

 

[AJshep]

With the greatest respect Stu. I'm with the others I think it's best to get someone qualified to look at this.
It's going to involve disconnecting and testing circuits, and I personally wouldn't want to advise someone over a forum especially when it could cause serious injury or death.

 

[Stuportsmouth]

The idea of this post is to find out if the rcd could be the possible fault or if it could be a fault somewhere else but surely with one wire direct feed when switched off the rcd doesn't trip meaning there shouldn't be a fault on the other circuits as it' been fine for over a week.

 

[ashrow]

40 amp mcb missing from rcd side so now on 16amp mcb on non rcd side and still tripping rcd. not possible if you are doing things correctly.
If there is a shower isolator check that for correct operation, tightness, burnt out etc etc.
If you been doing it from the age of ten i would not be posting on a forum for advice on basic fault finding. but good luck and happy showering

 

[Pete999]

With the greatest respect Stu. I'm with the others I think it's best to get someone qualified to look at this.
It's going to involve disconnecting and testing circuits, and I personally wouldn't want to advise someone over a forum especially when it could cause serious injury or death.

At last

 

[Stuportsmouth]

40 amp mcb missing from rcd side so now on 16amp mcb on non rcd side and still tripping rcd. not possible if you are doing things correctly.
If there is a shower isolator check that for correct operation, tightness, burnt out etc etc.
If you been doing it from the age of ten i would not be posting on a forum for advice on basic fault finding. but good luck and happy showering

The switch has also been replaced and basic fault finding steps have been looked at all earths neutrals and lives checked on box and nothing has been added or changed so just cannot understand how such a fault just appears the house was only rewired 2 years ago.

 

[Octopus]

The 16A MCB won't last long powering the shower ...

 

[Octopus]

The switch has also been replaced

Randomly changing parts does not replace proper fault finding .....

 

[Pete999]

The switch has also been replaced

Just change everything and then call an Electrician, advice has been given not accepted that's me gone from this thread, I suspect with the OP's agreement.

 

[Octopus]

Pete ................. you can lead a horse to water ..............

 

[123]

Randomly changing parts does not replace proper fault finding .....

And is generally a false economy, just to save paying a spark to find the actual fault in the first place.

 

[Des 56]

If the Rcd was faulty I would expect the same tripping problem for other loads that are used on circuits on the Rcd side of the board

I would expect to find a neutral-earth fault on the shower cable,but without having at least a insulation resistance tester you may be a long time finding the problem