RCBO testing

[pencilpusher]

Having read differing views about this test, can someone suggest the best way to test an RCBO. Can it be done at the end of say, the smoke alrm circuit or should it be done at the board using the RCBO terminals? Thanks.

 

[Guest112]

i dont think it matters although some may argue that you shouldnt have a cover off a live db but i find it saves time to do at the board especially when you have many rcbos in the board

 

[pencilpusher]

Thanks. That's the problem; some say you shouldn't have the cover off at the board and others say you shouldn't be using live terminals at the end of a circuit. I thought live tesing is sometimes required and "competent" persons should be able to justify it, when resonable?

 

[Deleted member 9648]

Thanks. That's the problem; some say you shouldn't have the cover off at the board and others say you shouldn't be using live terminals at the end of a circuit. I thought live tesing is sometimes required and "competent" persons should be able to justify it, when resonable?

Live working and live testing are two different things....you can avoid live working but you cant avoid live testing.
You should 'risk assess' the dangers when live testing,and carry out your tests in a manner safe to yourself and others....balancing at the top of steps trying to get the probes into the terminals of a luminaire while holding the meter may not constitute safe testing...testing at an open DB in a closed off area with approved live testing equipment may. Apply common sense.

 

[malcolmsanford]

^^^^^^^^^^^^^^ nail head hit

 

[Deleted member 26818]

Another problem being that the length of the circuit can affect the results, and unless you can safely leave your tester hanging there, it will be a lot of work running backwards and forwards to the CU to reset the RCD everytime it trips.

 

[Richard Burns]

The recommendation for testing a RCD (whether and RCBO or not) is to test as close as possible to the device. I would test at the terminals of the RCBO if it was a lighting circuit as it is safer to connect there.

 

[Dunc]

Always test RCDs at source however some manufacturers RCDs will not operate correctly when tested at the terminals. Have a look at this thread for more info.

 

[Engineer54]

You are proving the functions of the RCD device, not the installation, so you would generally conduct the tests at the RCD terminals. You only need to test/check downstream if you have proved your RCD device is correctly functioning but is tripping out, for no apparent reason when the circuit is energised. In other words fault finding on a suspect RCD protected circuit.
Nothing however to stop you testing RCDS from the circuit ends, but as others have stated, not the most convienient place to test, when you have to keep walking back to the CU to reset...

 

[telectrix]

when you have to keep walking back to the CU to reset...

that's what apprentices are for.:reddevil:

 

[pencilpusher]

Thanks to you all. PP

 

[ezzzekiel]

Although i agree with testing at source i would like to know where its stated that rcd / bo should be tested direct as every bit of literature i have seen always shows meter being plugged into a socket outlet for the test

 

[Des 56]

I agree with ezzzekiel
I dont think that there is a specific "thou shalt test at source" instruction

But to keep the sentiment alive

There is evidence that connected loads can and do give misleading results
To eliminate the chance of those misleading results,it would be worthwhile testing at source

here is information that may be of interest
Effect of load on RCD Test Performance report : Electrical Safety Council

 

[alanl]

612.8.1
"...verification...shall be made...for RCDs by inspection and test..... The disconnection times...shall be verified."

No other way than by live testing to verify that they meet the requirements.

Then you have the Electricity at Work Regs, which state adequate safety standards should be kept, so if a RCD was protecting a light circuit, you wouldn't really be safe putting probes on a pendant, 4 steps up a step ladder, then getting down each time to reset the RCD, so you'd use common sense, and do it at the DB/CU, where there would be no falling hazard, no moving from the spot to reset the RCD (you'd be leaving a live connection open at the pendant when you reset the RCD), and no hanging leads that can trip you., wrap around your leg, one could be inadvertently left on line, the other is dropped onto your leg, and there is potential for a shock through the meter etc.
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