RCBO faulty or not ?

[AndyPRK]

Is this a valid test?

I just wanted to do a basic test of an RCBO I had to see if the test function worked.

I connected it to a 13A socket.
When I pressed the test button the RCBO tripped, but so did the RCBO in the CU connected to the ring.

Do you think this is normal behaviour? I know you wouldn't design it with two 30mA devices in series.


Both RCBO's are the same brand.

 

[sparkybird]

I think you've answered your question - two RCD's on same circuit in effect will trip

How on earth did you wire up the rcbo under test safely???

 

[AndyPRK]

Just wondering if one is Working more quickly.

I got enough rcds about to be safe!

 

[ericmark]

The 100ma S type delayed RCD would trip in the main board when the test button was pressed on the 10ma RCD built into the work bench so nothing wrong there.

But to test a RCD you need to also measure time. 6 tests in all the first 2 at half the rated value with positive half cycle and with negative half cycle both should fail to trip the RCD.

At rated current again both pos and neg should trip the RCD.

And at double rated value again both pos and neg it should be under 40ms.

I fail to see how one can ever measure 40ms or ensure either pos or neg without using a proper RCD tester.

The test button is purely to ensure it can mechanical trip and is not a valid method of testing.

 

[ricicle]

The 100ma S type delayed RCD would trip in the main board when the test button was pressed on the 10ma RCD built into the work bench so nothing wrong there.

Did the OP mention a 100mA TD or 10mA built into a workbench