mcb tripping when doing zs test

Robo · Jan 20, 2012

What are the general reasons for why MCBs trip when doing zs tests. The R1+R2 wasnt very good and likewise with IR test

The Ranger · Jan 20, 2012

the R1+R2 wasn't good and the insulation resistance wasn't either but you still went onto a live test!

have a word!!

MarkieSparkie · Jan 20, 2012

MCB tripping usually happens with low nominal current rated devices (6 or 10A). The cause is the high current pulse and it's duration, that the tester uses to conduct the test <30A Peak. It is even possible in certain circumstances for some so called "no-trip" tests tripping MCBs, particularly if they employ DC blocking or if the pulse level and duration is long enough.

Deleted member 9648 · Jan 20, 2012

Robo said:
What are the general reasons for why MCBs trip when doing zs tests. The R1+R2 wasnt very good and likewise with IR test

You are asking for a pasting with that one mate......that aside 6a type B MCB's often trip on a high current test because the tester draws enough current to trip them,try a low current test if you have a meter capable of that.

Robo · Jan 20, 2012

I didnt mean bad enough to not continue with a live test. Sorry to miss lead. Just curiousd if that had an affect. appologies.

The tester didnt have a no trip facility. Thanks for the info

ezzzekiel · Jan 21, 2012

you said the readings were not good you didnt say they were not within range so i think on this occasion the response you recieved was a tad harsh.

to overcome the problem swap mcb for higher rated one for duration of test

The Ranger · Jan 21, 2012

ezzzekiel said:
you said the readings were not good you didnt say they were not within range so i think on this occasion the response you recieved was a tad harsh.

to overcome the problem swap mcb for higher rated one for duration of test

Really? we are supposed to be skilled people if the test was not good that would say to me they were not as expected for the install and I personally would want to know why and investigate further. This just will do attitude because i'm following what the book says is acceptable, when I know there is a issue really don't cut it in the industry we work in! to many people rely on books over there personal knowledge and instinct.