Discuss Conflicting informatiom in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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Plonker 3

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Doing a EICR today, and come across this MCB, but the stickers different from what is engraved on the side, could someone please give me the correct KA rating for this please.
 

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spark 68

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Both look like the Icn or breaking capacity is 10 000 (10kA), and Ics M3 (3kA) or switching capacity on paper label, but if it is part of a CU up to a 100A single phase, the Icn may be taken as 16kA.

See what others think.
 
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johnboy6083

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i had exactly the smae problem a few weeks ago, with exactly the same breakers. I think that the 10ka interrupting capaictyis the reated ultimate breaking capacity, in toherwords, the unti will not be useable after breaking a fault of that magnitude. the 3Ka is the load that it willbreak wand still be usebale again.

the DNO fuse will have energy limiting characteristics that will probably stop the fault currwent from reaching 10Ka though. maufacturers info is available
 
E

Engineer54

At a guess made for the American market, the 10KA relates to there NEMA/UL standards Whereas the M3 is the category that the BS institute has handed it. Very similar to MG (Schneider) breakers, ...look at the French KA ratings and you'll find that they can be very different from the BS ratings....

I may be wrong, but seen this many times in the past with European KA values in conflict to BS type ratings...
 
P

Plonker 3

Right then so I record it as a 3KA MCB, the PSCC of the DB is 4.5 KA what code does this need on a EICR?
 

spark 68

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I would have said the max breaking capacity or Icn is 10kA and this is present on both labels.

Icn = n for knackered, means it is capable of breaking this magnitude of fault current and is the absolute max capacity but will not work again after, this is the parameter for the EICR, for clearing the largest fault current that is possible (or pfc).

Ics is the max fault current it can safely switch and still be usable, in this case M3 or 3kA.

Ics = s for safely switch, which is still more than it's normal load and will probably not be exceeded on a fault downstream of this device.

The PFC diminishes the further away from the origin you get, due to the resistances of the conductors MCB etc.



see Johnboys post further back in the thread.
 
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Guest55

Icn = n for knackered, means it is capable of breaking this magnitude of fault current and is the absolute max capacity but will not work again after, this is the parameter for the EICR, for clearing the largest fault current that is possible (or pfc).

Isnt it the other way round ?
I thought the value recorded on the cert was its Ics ? the max fault current that leaves the mcb reusable ?
Its certainly the most useful data of the two.
 

topquark

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Isnt it the other way round ?
I thought the value recorded on the cert was its Ics ? the max fault current that leaves the mcb reusable ?
Its certainly the most useful data of the two.
Nope it's Icn, same as for the MCB/RCBO (normally 6k or 3k for the wylex plug in 3036 replacement jobbies).
 

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