RCD and RCBO not tripping

[Ross Trician]

morning folks, I have completed 2nd fix on an extension and have pit 2 circuits on to rcbo's to sgregate them from the rcd side and split up the circuits. (i.e, up lights, down sockets etc)

on testing the ring i get good continuity of L,N,E, figure 8 test ok, insulation is low but acceptable at 8megs, (it is not a complete new circuit it does incorporate existing to).

When testing rcbo it wont trip on auto test but will on ramp test but at something like 1550m/s.

the only thing i can find "wrong" is that all of the earthing seems to be interconnected across all circuits...

the consumer unit is a squarre d type, singe rcd split load board.

I am bit baffled, advise appreciated.

thanks, Ross.

 

[slocm3105]

bad rcd probably. But I have had problems with paralell earth paths causing an rcd not to rip before now.

 

[Des 56]

If all other tests are ok,test the Rcbo at source with the circuit dis connected

 

[ian.settle1]

morning folks, I have completed 2nd fix on an extension and have pit 2 circuits on to rcbo's to sgregate them from the rcd side and split up the circuits. (i.e, up lights, down sockets etc)

on testing the ring i get good continuity of L,N,E, figure 8 test ok, insulation is low but acceptable at 8megs, (it is not a complete new circuit it does incorporate existing to).

When testing rcbo it wont trip on auto test but will on ramp test but at something like 1550m/s.

the only thing i can find "wrong" is that all of the earthing seems to be interconnected across all circuits...

the consumer unit is a squarre d type, singe rcd split load board.

I am bit baffled, advise appreciated.

thanks, Ross.

When carrying out a ramp test it should give you the mAmps it trips at not time.

 

[Ross Trician]

soory, yes it was Mamp not time.

If the parrelel paths are the problem which are preventing it triping, is there a way around it other than trying to find the interconections?

could be a nightmare to find them eh!!!!!!

 

[Risteard]

soory, yes it was Mamp not time.

It was hardly ramping to 1550mA!!!

 

[ian.settle1]

It was hardly ramping to 1550mA!!!

Same as 1.5 Amps

 

[Risteard]

Same as 1.5 Amps

Yes but presumably the tester will quit after 30mA (presuming it's a 30mA RCD) if it fails to operate.

 

[Ross Trician]

you chaps have now got me wondering, I am sure the meter said 1550Ma, it is a megger 1552 meter. when i did the auto test it didnt trip at all, just said 1999Ms.......

That i presumably means that the test has failed to trip in a given time. it doesnt measure the ampage it trips at. that said, i am sure the ramp test measure tripping current so yes, it did say 1550Ma.

(I do appologise to you chaps that seem to find the question a bit "misdemeaner" but that is surely how people learn...including me and hope those of you who seem to know everything would alow those that dont a little slack........so as for answers like "it was hardly ramping at 1550ma!!!!, please dont bother to answer if you cant be constructive eh!!!!!!! )

thanks for your replies anyway..

 

[xraytek]

morning folks, I have completed 2nd fix on an extension and have pit 2 circuits on to rcbo's to sgregate them from the rcd side and split up the circuits. (i.e, up lights, down sockets etc)

on testing the ring i get good continuity of L,N,E, figure 8 test ok, insulation is low but acceptable at 8megs, (it is not a complete new circuit it does incorporate existing to).

When testing rcbo it wont trip on auto test but will on ramp test but at something like 1550m/s.

the only thing i can find "wrong" is that all of the earthing seems to be interconnected across all circuits...

the consumer unit is a squarre d type, singe rcd split load board.

I am bit baffled, advise appreciated.

thanks, Ross.

You mention continuity and insulation tests, but did you carry out any loop impedance tests?
I am wondering if there is a poor connection between the CU earth rail and an external MET where bonds are connected

 

[Risteard]

so as for answers like "it was hardly ramping at 1550ma!!!!, please dont bother to answer if you cant be constructive eh!!!!!!! )

I was trying to be constructive by suggesting that it didn't make sense to me and that perhaps you had mistyped or I had misinterpreted what you were saying. I wasn't having a go at you at all.

 

[Ross Trician]

Update on RCBO's not tripping..

Evening folks.

Just to give an update/possible explanation to the problem with RCBO's etc not triping.

I havnet yet completed the job I posted about earlier as they are away at the moment. I have however been today to some wors and a PIR for a client. The work involved changing some C/B's to RCBO's (as before) did dead tests, all very good results, come to do live tests and the RCBO tests and couldnt get the Flaming things to trip,,,,,,,Here we go again I thought....


I have, after some hair and teeth pulling found my problem and thought I'd share it (and yes expect some sarcy coments) so that if you experience similar problems it may help you out.


Problem was..............Operator/meter errror. I have a megger 1552 and the "milli amp" selector switch is not locating at for example the 30Ma slot properly, after some fiddling with it, it located properly and then tested fine......I will contact megger and see if there is anything that they will do to it....

Cant believe that its playing up and causing such grief and it's not exactly a cheap nasty meter...