It is currently Sun Sep 19, 2021 5:04 am



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Weakest link circuit breaker?
PostPosted: Wed Mar 03, 2021 3:03 pm 

Joined: Mon Aug 24, 2015 10:24 am
Posts: 29
Say I have a 480V branch panel with a main breaker in a panel that is rated 65kA , and a bunch of branch breakers each also rated 65kA. I also have a few branch breakers that are rated 18kA.

Is it 'correct' to consider the panel itself as therefore only rated at 18kA or at the 'weakest link' breaker wise in the panel? If my fault calcs indicated 20kA at the line side of the main breaker, the 18kA breakers are technically threatened since they are within the same enclosure, right? I should swap out those 18's for 65's. Does that sound right?

Thanks for your time,
Brian


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Wed Mar 03, 2021 3:17 pm 
Sparks Level

Joined: Thu Apr 18, 2019 11:42 am
Posts: 58
18kA. :shock:

Mike


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Thu Mar 04, 2021 5:36 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 851
Location: Rutland, VT
If the main breaker is rated at 65kA, I think the panel would be rated higher than the 18kA breaker as a manufacturer is not going to put a 65kA breaker in a low rated panel. I don't have the info with me but I believe standard panel ratings go something like, 10kA, 22kA, 42kA.

Did you see if that 18kA breaker is series rated with the 65kA breaker?

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Thu Mar 04, 2021 2:25 pm 
Sparks Level

Joined: Thu Apr 18, 2019 11:42 am
Posts: 58
Never know Barry...maybe someone came in after the fact and installed an 18kA breaker (seen it happen all of the time). Good point about series rating...

Mike


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Fri Mar 05, 2021 6:11 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 851
Location: Rutland, VT
Yes, Mike, I had thought of that and that is a reason why on all my labels, I include the short circuit fault current at that location. I hope it will help to stop under-rated breakers from being installed in panels.

By code, if it is a series rated system it needs to be labeled as such.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Mon Mar 15, 2021 6:40 am 
Sparks Level

Joined: Tue Jul 01, 2014 8:40 am
Posts: 106
Hi All, I agree with Barry, why would an electrical equipment manufacturer install a 65KA breaker in a much lower rated panel. It sounds like someone, perhaps an outside contractor has been installing some breakers in your panel without considering the short circuit ratings. If your fault current calcs indicate 20KA on the line side, then true enough that 18KA breaker could be threatened. Can you consult with the manufacturer or perhaps find out what the actual KA rating is of the panel and then install the correct KA rated breakers accordingly?


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Mon Mar 15, 2021 7:21 am 
Plasma Level
User avatar

Joined: Wed May 07, 2008 5:00 pm
Posts: 851
Location: Rutland, VT
Typically the panel SCCR is located inside the panel on a paper label. Many times I have seen this label non-existent in a panel, usually due to age of panel.

_________________
Barry Donovan, P.E.
www.workplacesafetysolutions.com


Top
 Profile Send private message  
Reply with quote  
 Post subject: Re: Weakest link circuit breaker?
PostPosted: Mon Mar 15, 2021 7:57 am 
Sparks Level

Joined: Tue Jan 19, 2010 2:35 pm
Posts: 152
A couple of options. First, I'd look at both symmetrical and asymmetrical fault current at the panel. It likely the asymmetrical fault current is higher. No matter, you'll be ahead of the game if you install that level AIC rated breaker or more. Most (newer) breakers have a maximum AIC listed on them. Depending on the manufacturer, your cost for a higher AIC rated breaker may not be much more than just getting the minimum rated AIC. You may end up getting something much better for a just little extra cash. Good luck.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 8 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883