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[Desmond.22]

Apologies for headline trying grab attention

So can someone help on this scenario.

Plant room prob 7Mx7M square ish. Loads of HVAC, pumps etc as you would expect and a ring final circuit.

Socket been damaged somehow and went to replace socket.

After replacing socket just for peace of mind we test that circuit. IR ok elip ok polarity etc.

Test RCBO and with cables disconnected as per GN3 all ok.

Just testing further and left loop tester on high current and the RCBO did not trip unusual so we got out RCD tester and couldn't get the RCBO to trip from socket. Yet with cables disconnected works as should.

So what going on and ae replaced RCBO and same ?

But circuit looks ok all in tact all tests on circuit as expected.

So unplug everything thinking maybe some item plugged in causeing problem but NO joy still.

Anyone ?

 

[curly]

What kind of tester do you have, is it possible you connected the CPC and neutral wrong on the tester ?

 

[Desmond.22]

What kind of tester do you have, is it possible you connected the CPC and neutral wrong on the tester ?

No mate megger 1721 we checked all stuff like that

 

[Bellendian]

What's the type of RCD? Is this a case that all this talk of needing type A or B rather than AC is having a practical impact?

 

[curly]

Did you try to trip the rcbo at all the sockets, just 1 or a few? Did you do a figure of 8 test R1 + R2

 

[Dan]

You tried turning it off and on again?

(Sorry I'm not a sparky )

 

[Wilko]

Hi - 2 thoughts - confirm again that N and E are separated so the rcd trip current returns via E to the earth bar and doesn’t rejoin N before the rcd - and if it’s an AC type rcd possibly loads are putting DC back through it and desensitising it. Good hunting .

 

[curly]

confirm again that N and E are separated so the rcd trip current returns via E to the earth bar and doesn’t rejoin N before the rcd

This is what I'm thinking. Looks like an alteration that's not been done correctly.

 

[James]

Might seem daft but are you sure the socket is fed from that rcbo?

Also as mentioned above, possible dc locking of the coil due to inverters or other equipment in plant room passing dc into mains.

 

[Desmond.22]

Definitely correct circuit and confirm the ring is complete and figure 8 test all good.

All in right place all through circuit L,E and N.

The dc from other stuff good shout so ill try turning off other stuff see if makes a difference.

Its all sockets on that circuit we even tried testing at the Type B rcbo 32A direct on terminals cables connected wont trip but connected out of RCBO and operates as should.

Now also question was would people class this as a defect as to gn3 i done tests correctly its only further testing thrown this issue up ?

 

[dmxtothemax]

Remember with RCD'S it's vitally important to keep neutral and earth seperate, probably an neutral to earth fault somewhere.

 

[marconi]

HAve you tried reversing the phase of the test current ie using the 0 and 180 deg positions?

And measure the N-E voltage at the RCBO output and socket. Most RCD testers do a pre-check of voltages and also check that the E/cpc will not rise above 50V when the test current is injected.

Is it a single or double pole RCBO?

 

[marconi]

Check N-E IR of the ring at the RCBO but disconnected from it with all socket switches in the on position and all loads unplugged.

Check ring continuity and compare readings of L-L N-N and E-E.

Does the ring supply equipment which is equipotential bonded to MET?

What is earthing system please?

What happened to cause damage to the socket and what was the effect of the damage?

 

[Midwest]

I've had similar with a neutral-earth fault before. Double check IR.

 

[mart spark]

Was I.R. testing done with all cpc and bonding connected at met? Was just thinking if there is a neutral to earth fault affecting the operation of the RCBO then this should show up on an IR test if done in this way