When testing a circuit protected by RCBO, do you test at the DB or furtherst point

[Sparky8898]

Hi, I just have a few questions in regards to testing an RCBO circuit

Is there a requirement to test at either the furthest point or the DB or is it down to the testers discretion.

Do the test results differ?

What tests on a circuit will trip the RCBO when you are away from the DB. Is it just the tripping times test?

Thanks

 

[Pete999]

Hi, I just have a few questions in regards to testing an RCBO circuit

Is there a requirement to test at either the furthest point or the DB or is it down to the testers discretion.

Do the test results differ?

What tests on a circuit will trip the RCBO when you are away from the DB. Is it just the tripping times test?

Thanks

Dis the circuit from the board and test from there.

 

[Deleted account]

If you mean testing the disconnection times of the residual current device at half, one and five times rated mA then it doesn't matter where you test from on the circuit.

I personally test at the board straight into the terminals of the device for convenience and ease. Why make things difficult.

 

[Deleted member 26818]

I prefer to test at the furthest point, so as to prove that the RCD/RCBO is providing the required protection.
I understand that some MFTs can struggle with this method, so most advice is to conduct the test at the RCD/RCBO.

 

[Silly Sausage]

PP, you've agreed with Pete, then said it doesn't matter!
Test RCDs as Pete says. The test is for the device, not the circuit.

 

[Ian1981]

At the DB.
Imagine testing on your own in a large commercial installation and having to go and reset the rcd every time you test on the 0 and 180 degree cycles If testing at the furthest point.
Plus there should be no load on the circuit so it’s more convenient at the DB id say.

 

[Deleted member 26818]

PP, you've agreed with Pete, then said it doesn't matter!
Test RCDs as Pete says. The test is for the device, not the circuit.

The reason I disagree with this advice, is:
Testing at the device does not prove that the device is functioning as intended.
If sockets require RCD protection, then the only way to prove the sockets have RCD protection, is to my mind test at the sockets.
Where circuits require RCD protection, again the only way to prove those circuits have RCD protection, is to test the circuit.

 

[Silly Sausage]

The reason I disagree with this advice, is:
Testing at the device does not prove that the device is functioning as intended.
If sockets require RCD protection, then the only way to prove the sockets have RCD protection, is to my mind test at the sockets.
Where circuits require RCD protection, again the only way to prove those circuits have RCD protection, is to test the circuit.

We've all had this discussion years ago, I, for one, am not going to change my stance that the test is for the device only. Any circuit(s) connected are separate entities that should be tested in their own right. Are you going to do speed tests on every circuit that is connected to an RCD?

 

[Deleted member 26818]

We've all had this discussion years ago, I, for one, am not going to change my stance that the test is for the device only. Any circuit(s) connected are separate entities that should be tested in their own right. Are you going to do speed tests on every circuit that is connected to an RCD?

Yes this is a recurring discussion, neither of us have changed our viewpoint.
Personally, I very rarely conduct Periodic Inspections and when I do, I charge for a whole day.
So taking my time and conducting a thorough I&T is not a problem.

 

[SparkyAndGeorge]

Some RCBO terminals are too deep for the probes on certain testers though so you'll have no choice but to test somewhere else on the circuit.

 

[Flanders]

Memshiled 2 rcbos fail if you test them at the board. fit a short length of cable to them and they test ok otherwise as other have said test and board or any where on the circuit, just need to make sure all loads are disconnect when you test it .

 

[KEV 1 N]

Memshiled 2 rcbos fail if you test them at the board. fit a short length of cable to them and they test ok otherwise as other have said test and board or any where on the circuit, just need to make sure all loads are disconnect when you test it .

Yes....they are a pain in the ar*e!

 

[UNG]

I prefer to test at the furthest point, so as to prove that the RCD/RCBO is providing the required protection.

My thinking as well.
If you apply a measured current / test to any point on a circuit with RCD protection then the device should IMO operate within the devices spec

I understand that some MFTs can struggle with this method, so most advice is to conduct the test at the RCD/RCBO.

Is it that MFT struggles or is there an underlying problem with the device that is not being identified


To add to this my question would be how many of us do a ramp test on a circuit with RCD / RCBO protection

 

[Midwest]

I just think its easier to test at a socket outlet, rather than taking the lid back off a CU and struggling to push some probes onto the RCD/RCBO terminals.

My MFT has a dedicated plug lead, and an auto function for the RCD tests. Don't most MFT's have these?

 

[ipf]

Either way, for me, whichever is easier..... I had an assessor telling me it had to be done at the device....but what difference between that and circuit points, after all, you are just testing RCD operation times, as required.
Ramp testing is a separate test, altogether.