RCBO's not tripping on High Current EFLI test

Griffin · Sep 13, 2011

Hi all,

Did a CU change today, now have 9 circuits are on 30ma RCBO's

A TNCS property with a ZE of 0.35........
16mm MEC
10mm bonding to gas and water
CU was from the Denmans basics range 12 way

Now all the RCBO's trip fine on when you test them x1 and x5, and when I did a ramp test they all tripped at around 23ma

But when I did a high current ZS test directly on the RCBO they no trip. They were all the same.

So I tried the upstairs and downstairs power at various socket..Still no trip on any of them

I have read a post from Sintra some time ago when he had a similar prob but there was no solution

any advice greatly appreciated.

Meter appears to be ok as it trips the RCD in my MK Sentry board at home!!

G :sad_smile:

WDMDL · Sep 14, 2011

Only thing I can think of is it's completely saturating the toroid in the RCBO resulting in very low output from the winding supplying the trip solenoid.

Could the toroid be too small to function correctly at higher differential currents?
If that's the case, it's a cause for concern - high current loop test draws about 10A or so in most cases, so a severe earth fault would not trip the RCD side, and wouldn't even trip a 6-amp for a very long time overcurrent wise.

Simon.

Knobhead · Sep 14, 2011

PM Sintra and see if he resolved the problem.

It is a very worrying situation and one that can’t be left as it is. Also contact Denmans, they should also be worried. By notifying them you take some responsibility off your shoulders.

oxocube · Sep 14, 2011

If your testing with 'no trip' turned on or a 'dlock' tester then they will not trip, turn of the no trip or dlock and they should trip. If not I would suspect your tester is faulty.

Griffin · Sep 14, 2011

Thanks for the replies chaps,

Fitted a Schnieder 16a type'C' RCBO in a 3 phase board today (this rcbo had the functional earth lead) and operated fine with all tests and tripped also on the 'high current ZS test'.

So my trusty 1652B appears to be fine.

My next plan of attack is to contact supplier and go back to property with one of the wylex RCBO's from the back of my van and retest using this. I find it hard to believe that all the RCBO's fitted from demnans are iffy!!!!!

Any other takers??

G

Griffin · Sep 14, 2011

Have never used 'Basics' before normally MK or Newlec if screwed on price. But this time no one else could get close to price.

Got visions of going back to change out at my own cost.........

Answers on a postcard...

G