MCB Breaking Capacity

[Duncan Bennett]

With regards to to BS7671, can anyone tell me where I might find values for the Breaking Capacities of Type B MCB's. I just can't find the answer to this one? :-(

 

[telectrix]

stamped on the breaker, generally 6000 in a box, i.e.6kA.

 

[Duncan Bennett]

DOH!!! Bit obvious.

My head is getting fried with these books.

Many thanks

 

[Engineer54]

MCB breaking capacities can be anything from 3KA to 25KA!! As Tel has stated, the breaking capacity is always indicated on the MCB device either in a box using all figures ie, 3000A or as a term, ..ie, 3KA

 

[telectrix]

or, with the older 3871 MCBs, it's denoted as M3,M6, etc., where the 3 or the 6 is the kA rating

 

[Duncan Bennett]

Thanks again, guys!

 

[Des 56]

You also have to be a spring chicken in order to be able to read the writing on the mcb as well :rolleyes4:

Either that,or use the bolt on eyes we unspringlike chickens have to use :sweatdrop:

 

[Paul.M]

With regards to to BS7671, can anyone tell me where I might find values for the Breaking Capacities of Type B MCB's. I just can't find the answer to this one? :-(

When you say "breaking capacities" of type B mcb's, do you mean the actual rating of, or the maximum breaking capacities under fault current?

Let's say you have a BS EN 60898 B32 mcb.

It's designed breaking capacity is 32 Amps (and up to 1.45 times its value for a maximum of an hour).

It's maximum Prospective Fault Current is (as above) printed on the mcb, eg 6000 or 6KA or M6. This means it can withstand a current of that value without being replaced. Any current above its maximum PFC would mean the internal parts of the mcb will be damaged and no longer suitable for use. Btw they can go bang as well.

If this is for college, look at what the question is talking about. You have all the answers on this thread.

 

[telectrix]

It's designed breaking capacity is 32 Amps (and up to 1.45 times its value for a maximum of an hour).

nope, that's it's rated load capacity In. breaking capacity is the kA rating, or max. pfc. as you say below.

 

[applemac]

sometimes printed on the side of mcb not front...

 

[spark 68]

If this is for college etc.,
the markings on the device are the max current (PFC) it can safely break, but the device may not be usable again, and should be replaced, this is the Icn value or the rated short circuit capacity in kA.

It will also have an Ics, or service short circuit capacity, this is the max current that it can safely break and still be usable, this is not marked on the device, and you will normally have to refer to the manufacturers data for this.

I only add this extra bit of information as there are sometimes questions on this (2391 etc.)

 

[Paul.M]

values for the Breaking Capacities of Type B MCB's. (

I'm only going by the question Tel.

B32= the "type and In" rating

[6] (in a box)= the Ics rating

6000 = the Icn rating.


Which "breaking capacities" does the op need? He doesn't ask for "maximum"?

Rather the op has put the full question down or It's another C&G play on words.

 

[Paul.M]

Spark 68 is quick on that keyboard lol. Good explanation mate.

 

[spark 68]

The way I was taught is Icn 'n' for Knackered, and Ics 's' for safe to re-use lol

 

[Jay Sparks]

The Ics is generaly a single figure in a square box, under the 6000 rectangle box, i.e on an MK B32 BS60898 the Ics is 3, which is the maximum current the device can interrupt and still be reset. Im not sure if it will have this box on any other make, as Ive only got an MK one knocking about. But I guess if the the Icn is 6ka then the Ics should be 3ka aswell........ But I dont make em so it could be different on other types...


Jay