SHOWER TRIPS RCD ITS NOT CONNECTED TO

[vitoboy]

Hi all

OK..did a cu change yesterday .. old wylex with an external rcd for a new amd3 dual rcd cu.

This morning the customer rings to say the shower has tripped the rcd.
Turn up on site..and the rcd that has tripped is not the one that the shower circuit is on.!
So i check for crossed over neutrals .. none.
i check with 500v IR test for connections between circuits between each rcd..none.

So.. the rcd only trips if the shower is running .. so i remove 1 element to check its not breaking down...all ok.

swap the elements ..all ok..

But any time both elements work together the rcd trips.

Put a clamp meter on the shower earth .. leakage just 8mA.

Ok ..im a bit stumped now...of course some interaction is going on between the 2 rcd's circuits .. but i cant measure any connection between them.

The install is in an old farm house 4 other dwellings around it all with TT systems including the 1 im working on.

Local supply transformer is in the field right next to the job .

All and any idea's please .

Many thanks in advance.

Vito

 

[Strima]

Loose supply neutral?

 

[Octopus]

accumulated leakage?

 

[Pete999]

Hi all

OK..did a cu change yesterday .. old wylex with an external rcd for a new amd3 dual rcd cu.

This morning the customer rings to say the shower has tripped the rcd.
Turn up on site..and the rcd that has tripped is not the one that the shower circuit is on.!
So i check for crossed over neutrals .. none.
i check with 500v IR test for connections between circuits between each rcd..none.

So.. the rcd only trips if the shower is running .. so i remove 1 element to check its not breaking down...all ok.

swap the elements ..all ok..

But any time both elements work together the rcd trips.

Put a clamp meter on the shower earth .. leakage just 8mA.

Ok ..im a bit stumped now...of course some interaction is going on between the 2 rcd's circuits .. but i cant measure any connection between them.

The install is in an old farm house 4 other dwellings around it all with TT systems including the 1 im working on.

Local supply transformer is in the field right next to the job .

All and any idea's please .

Many thanks in advance.

Vito

2nd Paragraph last two lines, what exactly do you mean by that statement? Agree with Strima could be loose N connection.

 

[marconi]

Are the white appliances (dishwasher, tumble dryer, washing machine, microwave) or electric hob (is it an induction hob?) - supplied by the RCD which trips?

Could you measure the L-E, N-E and L-N voltages at the CU main switch with the shower off and then on (all mcbs apart from shower one off) and let us know them? Shower on full flow and high heat so elements remain on.

 

[Midwest]

Global IR test result? And 8mA for just the shower.

 

[Midwest]

Another possibility, curtsey of @Richard Burns

 

[MDJ]

accumulated leakage?

this is also my opinion.

 

[vitoboy]

Neutrals in the cu .. all of them...are good.

Accumulated leakage ... wrong rcd for this.!

Cooker and kitchen ring circuit with all appliances is on the rcd that's tripping .. but that's not the one with the shower on it.
No induction hob..

Global IR test .. well the lowest IR for any of the circuit's is 60 meg ohms .. ..but the shower circuit is 999meg ohms.

Midwest... Yeh .. I've had this before ... but so far none of the circuit's on the tripping rcd side seems to have a significant neutral earth fault.

But so far I think this will be my next point of investigation. ..if only because I can't think of another.

Marcoi .. I could .. but what are you getting at with this..?

Thanks again for the input guys

Vito

 

[Yozza19]

Had exactly the same once turned out tncs system loose n in metre witch had recently been changed dam metre monkeys witch in turn under high load shower ect the high resistance made earth lower potential than n return try clamp metre on gas and water while shower is on or voltage indicator