rcd tripping

[colshaws]

Hi all.
Need some help,I fitted a new dual rcd board today and have problems with the RFC tripping the RCD. Test results for circuit are as follows, r1=.34, rn=.36, r2= .81 (r2 a little higher than expected but I think still o.k?) I.R= 10.6 M ohms.lower than I would like but still acceptable ( again I think?)
Connect circuit and energise and all is ok, start switching on appliances and RCD trips,I tried all appliances off and switching on one at a time hoping to find the fault but any combination can make it happen especially ones drawing a higher load.ie kettle or microwave. Disconnected all other circuits to eliminate borrowed or wrongly placed neutral, tried circuit on the other RCD but still trips. Any suggestions on the best way forward

 

[Guest111]

What current does rcd trip at on ramp test?

 

[colshaws]

RCD trips at 27ma

 

[Guest111]

have you clamped the earth to see what the cumulative leakage is?

 

[colshaws]

Dont have an earth leakage clamp meter

 

[Guest111]

oh dear,try dropping out the other circuits that share the same rcd,if it holds in then it could be cumulative leakage across the circuits sharing that rcd.

 

[colshaws]

oh dear,try dropping out the other circuits that share the same rcd,if it holds in then it could be cumulative leakage across the circuits sharing that rcd.

I have taken all circuits out of board completely, still trips

 

[tony mc]

Does it hold if you place a small load on the cct ?

 

[colshaws]

Does it hold if you place a small load on the cct ?

Yes, tv or alarm system, door bell etc its ok

 

[tony mc]

Try spliting the ring into two radials then energise them one at a time to see if one side will hold.

It could be a loose connection in a JB causing the RCD to see a imbalance .

I take it the items like the kettle hold on the other RCD so they are not leaking to trip it.

 

[tony mc]

I take it your EFLI test is OK and the RCD holds under test ?

 

[Guest111]

Agree with Tony,was just about to suggest that,nice one Tony.

 

[colshaws]

EFLI tested at 1 socket tripped RCD, but was ok at another,this socket also gave me a higher R1+R2 than others but was fine at terminals on back of socket so I changed the socket but didnt check ZS at this socket afterwards, by this time by head was begining to hurt.

 

[spark 68]

I have taken all circuits out of board completely, still trips

Do you mean every circuit is disconnected or just the RFC's ?, I am not sure what you mean here.

Have you checked the factory fitted split load connections ?, I have had the odd CU miswired from new before.

 

[tony mc]

If you rule out borrowed neutral and appliance plugged in not leaking then it has to be a fault somewhere on the circuit.

The RCD is monitoring the phase and neutral so any imbalance will be picked up and the unit will trip.

My bets on a loose connection at a S/O or a jointbox which is causing the havoc.

I would honestly invest in a earth leakage clamp as it will save you time in the future IMO !

Double check all your tail connections in the CU just to be sure !