AIC RATING
AIC RATING
(OP)
If a breaker has an AIC rating of 100KA ( for example) and it is exposed to a 30KA fault.
should the breaker still operate correctly after the fault 100% of the time OR does the 100KA rating insure that the breaker will operate for the said fault but there is no guarantee that the breaker will not be damaged?
should the breaker still operate correctly after the fault 100% of the time OR does the 100KA rating insure that the breaker will operate for the said fault but there is no guarantee that the breaker will not be damaged?
Ohm's it not just a good idea, Its the law.





RE: AIC RATING
For a typical molded case circuit breaker, the UL standards require only a very limited number of successful operations at the maximum fault current - I believe the number is six, but I'm not sure and I'm too lazy to look it up.
If the fault current is lower, presumably it is more likely to survive more fault interruptions, but there is no guarantee of anything.
As a minimum, I'd want to verify that breaker is still operating properly manually, with no obvious signs of damage. In an ideal world, the breaker would be tested after a fault interruption. In the real world, 99% of the time, if the breaker is still in one piece with no obvious damage, it will be closed back in and everyone hopes for the best.
David Castor
www.cvoes.com
RE: AIC RATING
"
what is the UL standard for this. the breaker in question is a SQD master pack NWH
Ohm's it not just a good idea, Its the law.
RE: AIC RATING
RE: AIC RATING
2. If a short-circuit has occurred, inspect the circuit breaker. Make sure all power is disconnected prior to inspection.
— Check the condition of the arc chambers (see page 90)
— Check the condition of the contacts (see page 90)
— Check the torque of the connections (see the connector installation instructions)
— Check the condition of the clusters (see page 90)
3. After eliminating the cause of the trip, reset the device.
RE: AIC RATING
thanks to all that responded.
Ohm's it not just a good idea, Its the law.
RE: AIC RATING
Keep in mind no actions are required following an overload (LT trip), just a fault.
Masterpacts have had a few issues and safety notices released, you may want to check out those also.
RE: AIC RATING
according to the lit. new masterpact breakers are designed to meet IEC 947-2
this is taken from page 10 of the attached document
______________________________________________________
IEC 947-2 & BS EN 60947-2
This standard replaces IEC 157-1,
applicable since 1973.
The circuit breaker selection criteria remain
unchanged, but the new standard provides
the user with a better guarantee concerning
quality and performance.
Circuit breakers are now subjected to tests
that are more representative of real
operating conditions.
Icu : the ultimate breaking capacity,
which must be greater than or equal to
the 3-phase short-circuit current at the
point of installation of the circuit breaker,
a value unlikely to be reached under real
conditions;
Ics : the service breaking capacity,
generally expressed as a percentage of
the ultimate breaking capacity (25, 50, 75
or 100 % of Icu). It corresponds to a
short-circuit current that is more likely to
be reached under real conditions. The
circuit breaker must continue to operate
normally after having interrupted a
current equal to Ics three times;
All Masterpact circuit breakers have a Ics
value equal to 100% of Icu.
_______________________________________________
so that tells me that a masterpact should be able to handle a fault of (100Kaic in this case) 3 times
Ohm's it not just a good idea, Its the law.
RE: AIC RATING
RE: AIC RATING
Rafiq Bulsara
http://www.srengineersct.com
RE: AIC RATING
My point for posting was to find out more info on just what the "expectations" are for the end user. I think that i have convinced myself that this is a SQD issue and not a end user issue based on the expectation of the breaker being able to meet the stated testing requirements.
can i get an amen?
Ohm's it not just a good idea, Its the law.
RE: AIC RATING
It should certainly be good for numerous 40 kA interruptions, at least that would be my position.
There are two UL standards for breakers - molded case and power circuit breaker - I believe the MasterPact can built to either one, depending on how it was specified.
David Castor
www.cvoes.com
RE: AIC RATING
One thing to keep in mind is that new breakers are not tested by the OEM, they only "batch test". That is why acceptance testing is always recommended.
RE: AIC RATING
Other than that, this is no different than anything else you own, with or without warranty. You will have hard time having mfr paying for the replacement, unless a manufacturing defect is proven. It is easier said than done. So, you need to weigh your options and costs.
Rafiq Bulsara
http://www.srengineersct.com
RE: AIC RATING
While breakers are obviously different, they have their own physics and one could envision time-integrated power behavior similar to fuses.
TTFN
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RE: AIC RATING
I think that is why Square D says as the 4th step to inspect the clusters after a fault operation. I think what they should have said is to inspect the clusters whenever the breaker has been racked out.
You can read their notification letter (attached).