Electronic Trip Units vs Manual Breakers

Having adjustable trip settings on breakers, especially larger ones, allows for better system coordination. When a fault happens, you want the breaker closes to the fault to be the first, and hopefully only, one to trip so that more and more of the facility does not get taken off-line in a disorderly way. If you have a fixed trip breaker, you may end up in a situation where the trip curve of that breaker is higher than one up-stream, meaning the upstream breaker may trip, shutting down more of your facility than necessary.

May be there is genuine fault on your load side and the breaker is tripping for a fault.Please eliminate the fault before coming to conclusion of replacing the breaker.Generally these micrologic breakers will have recording facility and you can see in the display why the breaker has tripped.

Relevant points, thank you. A little background, the breakers and trip units are going on 14 years old. (I'm told their active life is 12-14 years!) They are inspected yearly by an outside contractor. When they started faulting for no apparent reason (to us at that time) we called in an electrician to check them out. They were found to be tripping with less than 40% load and when we sent one out for testing, they were found to be bad. (whatever that means, I'm an ME so it's a little Greek to me) I can see the logic to having them trip before shutting everything down but in our application I don't know if it applies.

Any experience with manual breakers vs micrologic trip units?

We too experimented with micrologoc trip units in our GE AK power circuit breakers. We found them to be un-reliable even when new... Retrofit the old EC trip devices. The retrofit is relatively simple, we have done literally 100's (I work in a power plant so you can imagine how many thai means) The old ECs are reliable some having been in service for 30 years or more with just the recomended maintenance. Yes we test them regularly. Yes dear hearts sometimes older equipment is just better than the new stuff with all the fancy bells and whistles (But then I still prefer the simple, old, reliable Simpson analog meter...)