rcd will not trip

[mswesty]

hi i have the following problem, im open to ideas

16th ed board. 100ma old wylex stand alone rcd installed on the tails protecting all circuits , 30ma split in the board covering sockets shower etc as you would expect.
i had to connect a replacement shower cable from 6mm to 10mm afetr a bathroom refurb.

i arrive esstablish tt system 133 ohms possible to convert to pme (.31ohms) if required, carry out zs at shower unit along with ins res test, all good.
I then carry out rcd test and nothing trips.
i walk to board and re test NOTHING.
I decide it must be 30ma rcd and return with a new unit, install it and .. NOTHING.

I am unable to get either rcd to trip even in i apply test current at the 100ma wylex unit, i have checked my testers and they work.

i think i read somwhere that these old wylex rcd units work in a different way to modern ones, could they cancel each other out?? (magnetic operation)

my next visit will be my third and im open to solutions to save another trip.

any ideas??

 

[nickblake]

sounds to me like the RCD's are goofed try putting in a new one

 

[mswesty]

sounds to me like the RCD's are goofed try putting in a new one

hi thanks.
i have already tried the 30ma . no good.
my plan is to try the 100ma with a modern one tommorow .
cheers

 

[Mark_Burgess]

Do they trip okay when the button is pushed?

 

[mswesty]

hi yes both operate fine with the mechanical push button.
cheers

 

[Mark_Burgess]

I am with nickblade then.

 

[nickblake]

i have come across this before on a lighting circuit , it was caused by a loose earth once was remade it tripped have you carried out all the R1R2 tests and the readings are ok

 

[mswesty]

ive changed the 30ma i hope the 100ma change tommorow sorts this problem out!!!

 

[telectrix]

sorry to say but it looks like you are doing something wrong or your tester is faulty. try testing RCDat home to prove

 

[olly w]

Try switching all the MCB's off and testing the RCD'S on their own at the C.U.
I've known capacitors on equipment stopping RCD's from tripping.

 

[mswesty]

this board was fitted some 5 years ago. the owner says the 100ma occasionally trips.
a quick install has turned into a nightmare!!!!!!!
thanks again

 

[SimpleSimon]

Are they possibly 's' type RCD? Perhaps your not giving enough time for them to trip because of the time delay?

 

[mswesty]

naa
the tester finishes the sequence in alotted times . standard RCDs fitted even the new 30ma one i fitted from my supplier .
cheers again

 

[SimpleSimon]

Just to repeat an earlier question. Have you done R1 + R2 to prove continuity?

 

[malcolmsanford]

Is the 100mA RCD as you say outside the board itself on the tails coming from the meter? Chances are this may be one of the old ELCB,s. If it is a voltage ELCB then your RCD tester would not trip that, you would need one of the old Clare Loop testers to trip it as these induce a 50v test voltage across the coil. If it's a current operated one then it should trip with a RCD tester.

I'm assuming that as it's an older TT installtion you have some circuits on the non 30mA side .ie lights that are protected by that 100mA RCD/ELCB.

I know it's going to cost but I would change that 100mA to a newer RCD. This would mean fitting a MET block and taking the TT electrode earth conductor into that block and then coming off that block with your bonding, CPC to CU and so on. Then test both RCDs as mormal, think you may find it all works.