Testing breakers

[Eddiesparks]

Interesting that we dont test mcb's like we do rcd's. To see if they trip as according to their time/current curves. I'm guessing the practicalities of the test gear is why? Anyone else got any suggestions?!

 

[Meggerman]

Not Practical Mate. 60898 B Type MCB's need 5 X rated current to trip within 0.4 seconds. A 32A MCB would need 160A passed through it.

 

[Broken handle]

Is an MCB just a mechanical device whereas RCD is electro-mechanical?

 

[davesparks]

This topic has been discussed before, I'm sure a search will reveal lots of info.

But the basic problem is that to test it properly will make it unsuitable for continued use.
Manufacturers test samples from each batch, these samples are then thrown away after testing as they will be damaged by the test process.

 

[davesparks]

Is an MCB just a mechanical device whereas RCD is electro-mechanical?

Yes, purely mechanical, no electrical connections whatsoever!

 

[Eddiesparks]

Interesting. Amazing they are not all tested. There must be a few out there then (esp b&q £50 CU s) that wouldnt trip at the right time/ current surely?!

I know they are manufactured to a BS number but so are rcd's and we still test them.


Surely a variable resistor that you can stick across L and N would do the trick with a nice tasty BANG!!

 

[davesparks]

I'm sure I've said this already but testing them correctly destroys them.

 

[Engineer54]

You would only destroy/damage them if you passed a current equal or more than their rated KA breaking capacity. The main or overwhelming reason why they are not called on to be tested after installation, is the cost of the test kit that would be needed to test MCB's, eg, ''A Primary current injection'' test set... Were talking several 1000 pounds. MCB's are actually generally very reliable and a proven means of protection, far, far more reliable than RCD devices....

We test all our MCCB/ACB/GCB's etc on our main Distribution/Switchboards using Primary and Secondary injection testers, so we have the means to test any of our MCB's if they are/become suspect, but don't test them as a matter of course....

 

[GLENNSPARK]

here:

Miniature Circuit Breaker Test Equipment - MCB Testing

 

[Eddiesparks]

Cheers glenn i'll nip out and get one now