Replacing main breaker

[RRJ]

I have an old westing house 225 amp 3 phase 10kaic. I called Eaton to see what would be the replacement for it. They gave me an Eaton 225 amps with interrupting rating of 65KA. My question is: what happens when everything upstream is 10kaic and you replace a main with a breaker rated 65KAIC?


Sent from my iPhone using Tapatalk

 

[don_resqcapt19]

I has no effect on the system. All that means is that the new breaker can interrupt a fault current of 65,000 amps without exploding. It does not change the currents that the other breakers see. You can always replace a breaker that has a low interrupting rating with one that has a higher interrupting rating.

 

[RRJ]

I has no effect on the system. All that means is that the new breaker can interrupt a fault current of 65,000 amps without exploding. It does not change the currents that the other breakers see. You can always replace a breaker that has a low interrupting rating with one that has a higher interrupting rating.

Thank you, that’s what I thought but some one was telling me I was going to change the incident energy levels. But as long as upstream I have 10kaic I didn’t think it will change.

 

[Amps]

If it's a main breaker you may want to check with the utility company.

 

[Buck Parrish]

If it's a main breaker you may want to check with the utility company.

That would not be prudent....

 

[RRJ]

If it's a main breaker you may want to check with the utility company.

It’s a panel main. Not the main of the building.


Sent from my iPhone using Tapatalk

 

[mayanees]

Thank you, that’s what I thought but some one was telling me I was going to change the incident energy levels. But as long as upstream I have 10kaic I didn’t think it will change.

If you have labels downstream of the panel where you're replacing the main breaker, it may effect the incident energy (IE) of those downstream devices. If your labelling stops at the panel you're working in then no worries. If anything, I would expect the new breaker to operate faster, thus reducing the IE downstream.

 

[Engser18]

IMO, the KAIC rating won’t effect your system as soon as it is higher than the arc flash cal. The new breaker may effect the system due to other reason.

 

[jim dungar]

IMO, the KAIC rating won’t effect your system as soon as it is higher than the arc flash cal. The new breaker may effect the system due to other reason.

The AIC rating has no impact on anything once it is higher than the available fault current. AIC per se does not impact clearing time, however high AIC (65kAIC and higher) devices are often inherently fast.

 

[winnie]

You have 3 things to consider:

Actual available fault current at the breakers

Any series ratings in the existing situation

Fault incident energy at various locations.

You say that the upstream and downstream devices are rated 10 KAIC. If the actual available fault current is less than the rating of the other breakers, meaning that you have a 'fully rated system',
then the only requirement is that your new breaker exceed the available fault current.

But if the available fault current exceeds the breaker ratings, you may have a series rating situation. If this is the case then your new breaker needs to be rated for the available fault current with the existing breakers in series. 'Series rated systems' are only allowed with specific manufacturers testing.

Given your description of the upstream and downstream breakers, I suspect you have a fully rated system at the point where you are changing the breaker, but you don't say what the available fault current is.

Any change in breaker can change the incident energy. Because of the interplay between the various dynamic impedances of the breakers in series, incident energy can go up or down. This interplay is the reason that series ratings are required.

Changing the breaker probably means recalculating incident energy. If you have a fully rated system then the higher KAIC breaker is allowed but the change in breaker brand and rating probably triggers additional paperwork and label changes.

Jon

 

[Jraef]

If you have labels downstream of the panel where you're replacing the main breaker, it may effect the incident energy (IE) of those downstream devices. If your labelling stops at the panel you're working in then no worries. If anything, I would expect the new breaker to operate faster, thus reducing the IE downstream.

Interrupting capacity (kAIC) has zero relationship to opening time, incident energy or anything else like it. It ONLY has to do with the physical strength of the device and its ability to not become shrapnel in the event of having to interrupt a fault. If the old breaker was only rated 10kAIC, then there must not have been more than 10kA of incident energy in the system. 10kA < 65kA so it's not going to explode if there is a fault and has to interrupt 10kA.

Also, 10kAIC is the lowest rating available and is going to be the rating of even the smallest branch breaker anyway, so there would be no "series rating" with the existing breaker in this case.