RCD Fault?

[scoot1]

My brother (Who is a spark of 30years) fitted a split load CU in Oct last year.

2 days ago I developed the following problem:

The RCD is lined to 2 x showers, Upper sockets, Ground floor sockets, Extension sockets & Garage door which are all wired direct to MCB's.

Went to use the shower in extension and the RCD tripped. The MCB didn't. Reset RCD again, tried shower again & tripped again.

Tried to use hoover on all sockets (i.e. Ground, upper & extension). RCD tripped but none of the MCB's tripped.

Shower worked yesterday morning (RCD didn't trip). Hoover still won't work without tripping RCD.

RCD tripping infrequently for no apparent reason. During every trip, no MCB trips...............!!

Do I have a earth problem or is it a possible dodgy RCD??

 

[sm1thson]

Do I have a earth problem or is it a possible dodgy RCD??

sounds like a earth to neutral fault. although 2 showers on one RCD doesnt sound right, if there is a chance you have used both showers at the same time then it may not have done the RCD any good, what are its ratings? are these electric showers where the water is heated by the shower unit or just power shower pumps (from a tank of hot water).

 

[Spark123]

Agree, sounds like an N-E fault with a TN-CS supply. If you turn both showers off by the isolators does the hoover still trip the supply? If you unplug everything and then just plug the hoover in does it still trip? What else is on the RCD protected side of the board?

 

[scoot1]

Do I have a earth problem or is it a possible dodgy RCD??

sounds like a earth to neutral fault. although 2 showers on one RCD doesnt sound right, if there is a chance you have used both showers at the same time then it may not have done the RCD any good, what are its ratings? are these electric showers where the water is heated by the shower unit or just power shower pumps (from a tank of hot water).

Both showers are on completely seperate MCB's on the RCD side.
Both electric showers heated by the shower unit.
Both showers not used at same time. These have both been working fine for 6 months, as has the rest of the system.

The RCD is an 80amp 30 mamp.
Showers lines have had new earth tails put in and the MCB's are good enough to take upto 2 x 10.5kw showers.

 

[scoot1]

Agree, sounds like an N-E fault with a TN-CS supply. If you turn both showers off by the isolators does the hoover still trip the supply? If you unplug everything and then just plug the hoover in does it still trip? What else is on the RCD protected side of the board?

Haven't tried that yet but will do............
RCD side has 2 x showers, upper sockets, ground sockets, extension sockets & garage door.

Ta

 

[scoot1]

Agree, sounds like an N-E fault with a TN-CS supply.


Spark123.

Ta. Got NEDL in to check incoming earth and surprise, surprise it wasn't even connected. Problem solved.......................I can get back to doing the hoovering now & the missus can finish tiling the bathroom.

 

[scousespark]

Bit surprised your brother didn't spot there was no earth.
Also, having 2 showers could overload your main fuse.
Are you saying they can't run together, or that you don't run them?

 

[scoot1]

Also, having 2 showers could overload your main fuse.
Are you saying they can't run together, or that you don't run them.

He recognised the earth ZE reading was off the scale. Told me to check it out but I'm better at baking cakes than DIY!!
Trust him.........He's a good spark but unfortunately lives 300 miles from me.
Both showers have run together but don't very often. Earth tails upgraded and good MCB's in place to cover shower loading.

Ta[/img]

 

[Spark123]

My brother (Who is a spark of 30years) fitted a split load CU in Oct last year.

He recognised the earth ZE reading was off the scale. Told me to check it out but I'm better at baking cakes than DIY!!
Trust him.........He's a good spark but unfortunately lives 300 miles from me

No electrician should change a CU and leave a dangerous situation i.e. no earth, especially given he had measured it and there was a Ze reading off the scale.
I take it you have lost the certificates too?

 

[scousespark]

Leaving an install with no Earth is not something 'a good spark' would ever do.

As for the 2 showers, the individual MCBs protect single circuits.
A 40A breaker for a shower would be okay.

The problem with 2 showers is the total load on your supply is close to the max. Not a good design.

 

[scoot1]

Leaving an install with no Earth is not something 'a good spark' would ever do.

As for the 2 showers, the individual MCBs protect single circuits.
A 40A breaker for a shower would be okay.

The problem with 2 showers is the total load on your supply is close to the max. Not a good design

Ta!
I'll remember that when I do my next job and give you a call..........

 

[scousespark]

Ta!
I'll remember that when I do my next job and give you a call..........

Thought it was your brother who fitted it

 

[ban-all-sheds]

No electrician should change a CU and leave a dangerous situation i.e. no earth, especially given he had measured it and there was a Ze reading off the scale.
I take it you have lost the certificates too?

You don't seriously think that the kind of cowboy who would energise an installation with no earth and walk away would put his name to a certificate do you??

 

[Spark123]

Not really, which is why I asked! There's about as much chance of their being a certificate as there is it being notified to their LABC for part P.

 

[securespark]

Ta!
I'll remember that when I do my next job and give you a call..........

Thought it was your brother who fitted it

There is no "brother".....