Discuss RCD Test on lighting circuit protected by RCBOs in the Electrical Forum area at ElectriciansForums.net

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traineespark

Hi everyone, still training so please bear with me.

What is the correct way to carry out an RCD test on a lighting circuit protected by a BS61009 Type B RCBO?

I've looked in the regs, OSG and all of my course material but still no actual definitive answer so thought I'd ask here.

The reason I ask is that everything I've been taught to date as said that we only test live where it is save to do so, which is why Zs on lighting circuits is normally calculated rather than measured. That's all fine but you can't calculate the RCD test results.

Thanks in advance
 
The definitive answer to testing RCDs, is that you carry the tests out at the device with the outgoing circuit cables disconnected. (there are possibly some varying manufacturers variations)

So, you'll have to power down first to make your disconnections.
 
It is not possible to test the rcbo with no mains power, it is one of the live tests.
 
Thanks for your replies. So you are saying that to carry out the RCD test I should be doing the following (just checking I've understood correctly):-

1. Switch off main switch.
2. Disconnect L1 and Ln on outgoing side of RCBO
3. Power up
4. At the RCBO test between the L & N terminals and earth bar

Thanks again
 
This trips a lot of people up still to this day but as others have said test at the load side of rcbo or rcd. You are testing the device not the lights.
Edit
And yes make sure loads are disconnected.
 
One of the problems I have with conducting RCD tests at the board, is that they do not prove tha RCD will provide the required protection.
To my mind, an RCD installed at a board to provide protection for socket-outlets should be tested at the socket-outlets.
An RCD installed at the board to provide protection for cables concealed in walls should be tested beyond wherever the cables are concealed.
An RCD installed to provide protection for circuits of a location containing a bath or shower, should be tested in the location.
 
Look, about a year ago we had the same debate. At great expense to myself (if I say so myself!), I emailed several manufactures and organisations and the overwhelming majority were in favour of carrying out an RCD test at the end of the circuit.

I would have posted a link, but not intelligent enough to use the search facility here :) But you argue all you want, I will continue to test at the circuit end, or as near as.

For the OP, its one of the live tests. Testing a socket is easy enough, testing an RCBO inside a CU or at a lighting point, both have an element of risk. But you should be capable of doing given your training.
 
i'm with spin on this. RCD might perform perfectly when loads are dissed, but a neutral fault somewhere on the installation could prevent it from operating. the whole purpose of a RCD is to protect against accidental touching of a live part anywhere on the installation. therefore it should be tested as a real life situation, not dissed from the circuits. that's like something working in the lab. but failing in service. tin hat, where art thou?
 
I agree with the above, but when say replacing a DB I'll often fill it with the required RCBOs power up and test them all before connecting any of the outgoing cables. Hopefully insulation tests will identify any neutral problems, but some electronic equipment can upset RCDs, how far do you go, plug in and switch on every load in the installation before testing?
 
Cripes.... if you can't do this safely, you shouldn't be meddling with lecky!

Just noting that for all the effort of getting the screw-ins it still means you have to access near live terminals. That said, it's a nightmare holding three leads in the air while pressing a button so those screw-ins are worth their weight.
 

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