BG RCBO ramp test on one of them shows trip at 15ma every other one is 24 ma

[Dave OCD]

I think if there was any sort of interconnection between the circuits both RCBOs would be tripping constantly when current was drawn on either circuit.

 

[The Ghost]

both RCBOs would be tripping

That is an interesting and potentially valid view. Certainly food for thought.

 

[The Ghost]

The BG RCBO is the new compact type and only has a neutral fly lead by the way.

 

[The Ghost]

This is where you need an old style rcd tester

 

[westward10]

I think if there was any sort of interconnection between the circuits both RCBOs would be tripping constantly when current was drawn on either circuit.

I agree but never say never.

 

[westward10]

View attachment 43390

Nice meter Vorts, not sure that is safe to use on the fast trip anymore as it could create dangerous voltage across exposed metalwork.

 

[The Ghost]

dangerous voltage across exposed metalwork

I know it sounds crazy but many years ago when we did this test we had to make sure everyone in the house kept away from metal work radiators and x bonded pipes and had to almost shepherd them to the middle of the room while doing it.

 

[marconi]

Just wondering - what is the earthing system, what is EP bonded to the MET, any supplementary bonding still in place, and have you measured the N-E voltage at the CU for no load (Main Switch off), and before and after an RCBO trip for the four combinations of the two RCBO closed/open states? Are any equipments or socket strips with EMI filters present?

 

[marconi]

No mention by you yet but I assume you checked the ground floor socket at back of house and run to it off the up FRC (#3) and inter FRC IR and found nothing untoward.

Could you also test for PEFC and PSSC:

a. Supply
b. Sockets on Up FRC
c. Sockets on Down FRC

to see if you have a higher resistance neutral path for 'return' currents (cf RB's #6).

You mention the Tv and lamp(incandescent, CFL or LED?) when switched on (no cpc) cause the up FRC's RCBO t0 trip. Makes me wonder if you have a high resistance Neutral path or connection which is shown up when a brief high current (ie: the surge when TV powered up) flows - I'd try kettle on up FRC and measure L-N and L-E voltage at the socket it is plugged in to and also observe up L-N and N-E at CU as kettle turned on. I am wondering if the brief drop in L-N or rise in N-E pd is being detected by RCBO as a loss of neutral (but then one might expect the down FRC RCBO to trip too albeit it is not biased by the 8mA earth leakage).

No doubt you have thought of doing FRC standard tests.

Happy hunting. Better wear your deer-stalker hat!

 

[The Ghost]

These are the figures from the EICR RFC IR order LN-LE-NE r1-rn-r2 (first three figures). Thanks @marconi for your input. Ze is 0.16 PEFC 1.4 kohm. The earth DNO supplied was TN-S converted to TN-C-S with braid from outer sheath in there with the neutral. I suspect the utility room socket and the way it has been supplied as this is part of an extension and looking at the lighting in shower room, very poor wiring (see pic). Going back Monday now to get to the bottom of this problem. As you can see tests have been done as I did an EICR before fitting a new box. The client is about to go to Australia for a year and is renting the premises and wants a satisfactory cert. for the estate agent. So I have time to sort this and it is a semi empty house at the moment. But it is going to be a bit of a shock on the pursestrings methinks. Just musing... I wonder what the position would be if I changed all RCBO to RCD and did not supply RCD at all? After all I am required to leave the property no less safe then when I started. And in fact it would be much safer as the fuse carrier for an ex shower had gone into melt down due to replacing fuse on a short under load, i.e. not switching off the main switch. MCB would obviate this problem.

 

[The Ghost]

OK went back and sorted it. Managed to get it down to middle room spurred socket opened it up and neutral and earth connected incorrectly. Owner had installed a couple of sockets. Didn't take long at all. Thought I would be under the floorboards all day. Phew!

 

[marconi]

So Richard Burns was spot on - an N-E fault as a result of N and E reversal at a spurred socket, which was switched on (dp switch?) or switched on or off(sp switch)on the up FRC with an appliance plugged in to it using L,N and cpc?

 

[The Ghost]

In fairness to @telectrix as @Richard Burns acknowledged Tel got it. And Richard illustrated it. But otherwise that is about the size of it @marconi

 

[telectrix]

the important thing is always the result. ( as Croatia said after the semi-final).