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Is it acceptable, using a two-wire RCBO tester, to test at a light switch using the phase and earth wires?
If it is acceptable are there any disadvantages?
 
it's acceptable, but RCBO should be tested at it's outgoing terminals with no load applied.that way, you are testing the RCD itself without any interference from the circuit.a ramp test could be erroneous if there are any loads with integral leakage on the circuit.
 
It could be a long night, and I haven't any pop corn. :)

We've had this debate many times before, and my recollection of the guidance given by manufactures, schemes and the like is vague, but I seem to recall it was split 50/50, with the other side of the debate stating it should be tested at a point on the circuit. Whilst the test is verify the function of the device, also it confirms its functioning with the circuit it has been connected to.

I agree with loads being disconnected, by the way.

Edit; GN3 isn't clear exactly, I believe? But this piece from the IET states 'Tests are made on the load side of the RCD between the line conductor of the protected circuit and the associated cpc. Any load or appliances should be disconnected prior to testing';

Inspection and testing of electrical installations: residual current devices - https://electrical.------.org/wiring-matters/issues/50/inspection-and-testing-of-electrical-installations-residual-current-devices/
 
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I thought MW did a great job stating the situation, so I've a awarded a belated like, like.
 
I thought MW did a great job stating the situation, so I've a awarded a belated like, like.
He’s stated the situation, but not explained why he disagrees with Tel.
Does he disagree that it’s acceptable to test at the switch, or does he disagree that the test should be done at the terminals of the RCBO?
 
If I'm there to swop out a busted outlet I'd have to say I'm likely not isolating the whole installation to open the the board and remove conductors to test the RCD. Shall I get back on my horse and ride off?
 
If I'm there to swop out a busted outlet I'd have to say I'm likely not isolating the whole installation to open the the board and remove conductors to test the RCD. Shall I get back on my horse and ride off?
Well, to my mind, if you’ve installed a socket which requires RCD protection, then you should be testing that the RCD provides protection to that socket.
Testing the RCD at it’s outgoing terminals doesn’t prove that the RCD will provide protection to the socket.
 
I'm not saying now (edit 'cos I already have). Just to annoy you. :)
 
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Telextric, as I understand it, you are saying that testing at the switch is acceptable but that testing at the outgoing terminals is preferable.

Do you think there is ever a case for using both methods?
 
I always test at the load side of the rcbo with finals disconnected but also like to test at the furthest point ,be that a socket or light etc.
 

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