Check them cheap circuit breakers.

[Derlyn]

Hi All

When a circuit breaker seems a bit on the light side, both weight and price wise,
better you check it out lekker before using.

Check this out.
https://www.youtube.com/watch?v=2TJEzdqtXlQ

Peace out .. Derek

[recre8]

Hi All

When a circuit breaker seems a bit on the light side, both weight and price wise,
better you check it out lekker before using.

Check this out.
https://www.youtube.com/watch?v=2TJEzdqtXlQ

Peace out .. Derek

I recently replaced all my breakers with nice Schneider Easy 9 ones. The ones I took out are also labelled DZ47 (same as in the video). It seems like a number of these SA brands just white-label those cheap nasty breakers.

[Frans400]

Somehow related to this post I want to ask hou you guys test that your cb still tripping on the rated current ?

[AndyD]

Testing that a circuit breaker is tripping correctly according to its curve isn't easy and it's not a test your average electrician is expected to do. To test them properly you need a primary current injection rig. There are portable units available but last time I saw one for sale it was USD18k (about R300k) and that was second hand. I'm sure they're available here but I've never seen one in this country.

In theory you could do very basic (uncalibrated) trip tests on an MCB using a big battery with a current regulator and a stopwatch. Because current is a physical flow of a number of electrons per second regardless of the voltage there's no reason you can't test an MCB at 12 volts. Something like this Hawkins battery tester will get you halfway there if you fancy building your own rig.

[Justloadit]

Testing that a circuit breaker is tripping correctly according to its curve isn't easy and it's not a test your average electrician is expected to do. To test them properly you need a primary current injection rig. There are portable units available but last time I saw one for sale it was USD18k (about R300k) and that was second hand. I'm sure they're available here but I've never seen one in this country.

In theory you could do very basic (uncalibrated) trip tests on an MCB using a big battery with a current regulator and a stopwatch. Because current is a physical flow of a number of electrons per second regardless of the voltage there's no reason you can't test an MCB at 12 volts. Something like this Hawkins battery tester will get you halfway there if you fancy building your own rig.

MMmmmm Andy, I agree that you can test with a lower AC voltage, however I will disagree with you in using DC to test the AC breaker. The issue with the DC is that on breaking the contacts the arcing would damage the circuit breaker, secondly the magnetic coil part of the circuit breaker is designed for an AC supply, which differs considerably to a DC type coil.

What I have done in the past, which is a limited to trip current testing, requires that you have a 15A variable transformer, a 1.5KW transformer with a 10V secondary to be able to test up to 150Amps. An AC ammeter which has a minimum of 150Amp shunt.
You would then turn the variable transformer to minimum, connect the circuit breaker across the secondary of the transformer with the shunt in series, and then slowly turn the variable transformer up.
Watch the amp meter and watch the amps to the point the circuit breaker trips. You can use a smaller KVA rating transformer for smaller circuit breakers.

Testing three phase circuit breakers simply connect all three breakers in series and connect as above.

[AndyD]

Yes, DC would only test the general overload thermal trip and DC testing would certainly take its toll on the contacts. I wasn't suggesting running 5 times the In current rating of a C curve breaker to test the mag trip (hence the stopwatch suggestion).

A 3-phase MCB should open all 3 poles if the current through any single pole reaches the tripping curve so if I was testing 3-phase MCB's I'd probably test each pole separately. Testing them simultaneously in series wouldn't guarantee all 3 poles are tripping correctly.