MCB Breaking Capacity

[Risteard]

Some, but not all mcb's also have the Ics value marked on them, the Wylex and Square D single phase ones I have here do not have the Ics value marked, but some of Jay's did.

That may well be the case. I must have a look through mine and see which ones do and which ones don't display it.

 

[Jay Sparks]

Risteard,
I think we are talking at cross purposes here, the 6000 or 10000 in the little box is marked in Amps, this is the Icn value usually given as kA, eg 6 or 10 kA, the In is also marked in amps eg. 6 or 32 or whatever.

Some, but not all mcb's also have the Ics value marked on them, the Wylex and Square D single phase ones I have here do not have the Ics value marked, but some of Jay's did.

I think what Risteard is saying, is that the Ics on some mcbs is in fact given in ka. I.e the ones Ive got show a number 3 in a little box, Which is 3000A or 3ka. This half the Icn (6000A or 6k) which the mcb will interupt but will prob not work again but if it interupts at 3000A or 3ka then it may be still useable.
Hope this made sense, its sunny, warm and Ive been in the garden all afternoon with a few beers....
"Summer, summer, summer time..." (Fresh prince)

Jay

 

[spark 68]

That is what I meant Jay, when I said we were at cross purposes, as I don't have any MCB's to hand with the Ics marked on them.

At this point in time I cannot say if the Ics is is normally present or not, it may be that the Ics is usually marked on 3 phase MCB's but not on the single phase ones ?, but the Icn is always shown

 

[Jay Sparks]

The mcbs I have are all single phase. But as you say they dont all have it on them, I also have a few Wylex rcbos kicking about and they dont have it on. I suppose if you really needed to know the Ics of a particular device, then you could always ask the manufactuerer....


Jay

 

[Risteard]

I think what Risteard is saying, is that the Ics on some mcbs is in fact given in ka. I.e the ones Ive got show a number 3 in a little box, Which is 3000A or 3ka.

That's exactly what I meant! I probably didn't express it very well in fairness.

 

[Meggerman2391]

HiJust like to throw a curve ball here, according to latest on site guide if I were to use an 6amp, 60898 mcb, icn 6ka ics 3ka, would I need to increase my cpc to 2.5 mm2 csa? As 1.00 mm2 doesn't comply. Or would I need to find an mcb with a lower breaking capacity.?

 

[JUD]

HiJust like to throw a curve ball here, according to latest on site guide if I were to use an 6amp, 60898 mcb, icn 6ka ics 3ka, would I need to increase my cpc to 2.5 mm2 csa? As 1.00 mm2 doesn't comply. Or would I need to find an mcb with a lower breaking capacity.?

That would depend on the PEFC of the circuit in question. Just because the Icn is 6kA doesn't mean that the PFC will be 6kA (or even 3kA)

By the way the min cpc size for 3kA is 8.25mm² and for 6kA is 16.5mm²