Testing a RCBO

[STI]

Ive not tested one of these before. So from checking the RCD perspective is it the same as testing an RCD. Also if the RCBO is protecting several circuits do you disconnect the neutrals of the circuits not being tested before carrying out the test on an individual circuit.

Sorry just read another post asking a similar question and the answer to my first question is yes but still would like clarity on disconnecting the neutrals of the circuits protected by the RCBO but not under test at that time
Thanks

 

[RF Lighting]

You should test ALL RCDs in isolation.

 

[STI]

You should test ALL RCDs in isolation.

RF, what does that mean exactly. If i have understood you correctly you are saying disconnect everything from the RCD and test it. Ok i can see this would prove the RCD is working but what that doesnt confirm is that lets say a radial circuit which is on the RCD side is wired correctly and would trip the RCD.

If all the tests are carried out in the correct order it is possible to confirm polarity with the continuity tests. Then later do the insulation test reconnect incorrectly. So surely the RCD should be checked through the circuits it protects also?

 

[Taylortwocities]

No, the RCD tests check that the RCD itself disconnects in the times specified. It has nothing to do with the circuit (s) connected to it.

If you have a circuit connected and there is earth leakage then it will skew your testing because (for instance for a 30mA RCD) ) the ½Δn test should be at 15mA. If you had 10mA earth leakage on the connected copper the test could then be at 25mA and you may see the RCD trip when it should not do so.

You should do the tests in the proper order. Insulation testing is near the beginning and RCD testing is near the end.
If the RCD trips when you connect up the (tested) circuit this would be a part of the functional testing. Then you have a problem to sort out!

 

[Spark123]

It also takes any capacitance of the circuit out of the equation and stops it messing up the RCD tester readings.

 

[STI]

Thanks all for the resplies. I understand what is being said but a couple of other questions.

Do you ever check the RCD via the connected circuits eg a ring. I ask for two reasons firstly this was how i was taught to do it (plug in/attach your tester at the furthest point and record slowest time for 0 and 180 at 1 and 5x) and secondly if you dont, what figure do you put in say either a certificate or a PIR where it asks for the trip times specific to that circuit. Do you just put the isolated RCD times ?

 

[holmslaw]

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