mccb tripping

[dave-gardiner]

horticultral lighting circuit - 14 x t/p 16A mcb's each mcb has 6 x 600w 400v son lights, fed from a contactor which is fed by a 160A merlin gerin mccb. across the contactor measures L1 - 130A L2 - 133A L3 - 132A but after 6hrs the 160A trips. any ideas ? there is another 2 identical systems in the same cabinet working ok. system has worked ok for last 12 months.

 

[Guest123]

I have only seen these on youtube but from that have managed to get a grasp of what they are about but i would like more knowledge of them so i will be sure to ask the lecturers about them at college.....

Have a look through the PDF, page 14 onwards has info on 60947-2 MCCB's.

 

[Engineer54]

I have only seen these on youtube but from that have managed to get a grasp of what they are about but i would like more knowledge of them so i will be sure to ask the lecturers about them at college.....

Go onto the MG website, they have some very good reference material, it will probably tell you a lot more than your lecturer at collage. It obviously based on MG equipment, but it will be generally the same for all manufacturers MCCBs, ACBs, GCBs, etc. That's if you can get onto there website!!...lol!!

 

[dave-gardiner]

there 84 units on this mccb. The Amps are roughly the same as the 2 other mccb 's next to this one. Putting on one mcb and measuring at mccb at a time all 14 mcb's are the same.

 

[Guest123]

there 84 units on this mccb. The Amps are roughly the same as the 2 other mccb 's next to this one. Putting on one mcb and measuring at mccb at a time all 14 mcb's are the same.

This particular MCCB wouldn't happen to be the middle one in a column of 3 without spacing would it???

 

[Engineer54]

There is one sure way to find out if you have a dodgy MCCB and that is to swap it over with one of the others. If the fault transfers to the other circuit, it's down to a new MCCB unit!!


Is it possible to swap with one of the other units on this installation??

 

[dave-gardiner]

yes. i wonder if a look with a thermal imager would show if the unit is getting to hot!

 

[Marvo]

If it runs for several hours without tripping then it's not really the kind of fault I would go after with a thermal imager. Maybe a current logger would be a better weapon of choice.

Am I right in assuming that none of the t/pole 16A MCB's are ever tripping along with the 160A main breaker?

 

[dave-gardiner]

that is correct, just the one mccb 160A

 

[Marvo]

Have you checked the lugs and bolts on the connections top and bottom, If they're getting warm enough to cause nuisance tripping you would feel it by hand after the system has been running a while if you isolate the power. There would probably also be tell tale signs of heat on the pvc insulation near the lugs.

Otherwise as engineer54 suggested try swapping out the breaker with an identical one from another system to prove if it's faulty. I have to say though that Merlin Gerin equipment is pretty damn reliable, I'd bet my lunch it's not a faulty breaker.