Breaker upgrade ? Do it with the cheapest ?

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Davebones said:
The utility upgraded a 1500 kva transformer to 2500 kva . They said our AFC went from 32k to over 53k . These two breakers are only rated 50k ( P frame 2000 amp ) . The ones they recommend replacing them with are ( Power pact R-frame 2000 amp 65 AIC ) .
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I don't see a 50kA AIC on any P frame, and you can get P frame up to 100kA. What is the actual catalog # of your breakers?
 
Davebones said:
Had a arc flash study done on our facility last year . It showed two ( 2 ) 2000 amp main breakers that needed to be upgraded . This is in a 4000 amp SQ D switchgear . Sq d looked at this and gave us a quote to replace and also retro fit the bus to accommodate the new breakers . Being what this is I told my boss I would recommend going with Sq D as it is their type of switchgear . Purchasing is now involved and they want to go online to find someone to do it cheaper . Not thrilled to go with the cheapest when it comes to doing a upgrade like this . Wondered what we should consider when we get quotes to do it cheaper ??
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Purchasing don't understand why there are problems in the first place, all they see is dollar signs and a decrease in bottom line. You need to give them a worst case scenario of what the potential liability cost of this condition or even any other non properly engineered solutions might be and then have them decide what kind of a gambler they are.

Could be the cheaper solution is to move the transformer further away and leave the gear in question as is.
 
There's no way to relocate transformer . We have 5 on site . Best way to deal with this is to replace these breakers and modify the bus . Wanting to go with the cheapest is what I'm concerned about . If there ever was a issue I would want Sq D sitting next to me at a inquire .
 
wbdvt said:
For an arc flash study, if there is an overdutied protective device that is doing the interrupting for an arc flash event, that needs to be ignored and the next upstream device used.
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Can you offer proof that this is actually a written Standard?

I am in a somewhat argumentative mood, thank you debates.
The NEC requires devices to have ratings high than the bolted fault current available on its line side terminals. But the NEC does not require existing installations to be upgraded.
It is absolutely impossible, for a <600V arcing fault to to be close in size to a bolted fault. So, an overdutied device might easily be able clear an arcing through fault.
 
jim dungar said:
Can you offer proof that this is actually a written Standard
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No it's not a standard but is done by experienced engineers on arc flash studies. The closest I can come to a standard for you to reference is a IEEE paper titled "Arc-Flash Hazard Analysis of Power Systems with Overdutied or Series Rated Equipment", by Mark E. Johnson, PE - GE Energy Services, #978-1-4673-0409-2
 
wbdvt said:
No it's not a standard but is done by experienced engineers on arc flash studies.
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I know many engineers and firms that do not share your opinion.

The report should be based on facts, assumptions should be clearly identified.
It is perfectly acceptable to recommend, and even encourage, overdutied equipment be changed, it is something else to say it is required or mandatory.

Safety does come first, but I do not like fear mongering.
 
wbdvt said:
No it's not a standard but is done by experienced engineers on arc flash studies.
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I know many engineers and firms that do not share your opinion.

The report should be based on facts, assumptions should be clearly identified.
It is absolutely acceptable to recommend, and even encourage, overdutied equipment be changed, it is something else to say it is required or mandatory.

Safety does come first. We need to be conservative, however we also need to do a better job of analyzing risk rather than simply identifying hazards. I do not like base fear mongering.
It seems we spend a lot of effort focusing on the .001% risks while all but ignoring the 99.999% ones.
In an operating and properly maintained system, what is the likelihood that a bolted 3-phase fault is going to occur versus that of a 1-phase line to ground arcing fault?
 
wbdvt said:
I would double check the report to see what value of fault current is being used to determine the overdutied equipment.
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I agree. My first move would be to see if that Fault current figure was provided by the utility, or the actual value based on the transformer nameplate. Utilities will typically quote a much higher than actual value.
 
electrofelon said:
I agree. My first move would be to see if that Fault current figure was provided by the utility, or the actual value based on the transformer nameplate. Utilities will typically quote a much higher than actual value.
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What I tried to do in my previous post wp outas to avoid needless time that is waisted to calculate actual fault current which may not gain you anything such a going from a 14kaic breaker to a 30kaic breaker. If the actual kaic based upon he available fault current based upon unlimited fault current on the pri. Is equal to or below that breakers kaic rating you can stop there but you still must consider the beaker ratings down sterean. As they too mî
 
templdl said:
What I tried to do in my previous post wp outas to avoid needless time that is waisted to calculate actual fault current which may not gain you anything such a going from a 14kaic breaker to a 30kaic breaker. If the actual kaic based upon he available fault current based upon unlimited fault current on the pri. Is equal to or below that breakers kaic rating you can stop there but you still must consider the beaker ratings down sterean. As they too mî
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Sorry, my post was incomplete as I had to step away it timed out N me.
What I tried to do in my previous post was to avoid needless time that is waisted to calculate actual fault current which may not gain you anything such a going from a 14kaic breaker to a 30kaic breaker. If the actual kaic based upon he available fault current based upon unlimited fault current on the pri. is equal to or below that breakers kaic rating you can stop there but you still must consider the beaker ratings down sterean. As they too must have a. Kaic ratiing equal honor less than than the faultcurrent that the main breaker was based upon which is called being fully rated. Should hat a value be above then you will find coordination study to determine what the actual available ka would be at each one of the down stream breakers and gthrogh th same considerations you did ewhen justifying the main faic rating.
The key is to never needlesly taking the time to do ka calculation if it doesn't gain you anything. If you go from a 14kaic to a39kaic device and the max ka at the transformer secondary is 28ka then busting your butt to calculate 25 or 26ka is not going to change the 30kaic rated breaker. Doing a coordination study only gains something only if the ka is above the 30kaic rating and you need to consider going up to a 42kaic, the next higher rated device. In taking the time to do a coordination stidy there may be a chance that the actual available ka at the device is less than the kaic rating of the device which then justifies the need not to go up to a 42kaic device.
Without doing a coordination study all devices down stream of the main breaker must be fully rated for the available ka where each device is located.
If luck is on your side the devices down stream from the main breaker may have a "series rating" with it which may justify the need to have to up to athe next higher kaic rated device.
This may have been a long post but this is the thought pattern that must be considered when justifying he kaic ratings of each device when changing the available ka current at the service entrance.
 
wbdvt said:
I would also encourage you and others to visit Jim Phillips (IEEE 1584 Committee Member) ArcFlashForum.com and do a search on overdutied equipment and what is being done.
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Like Paulengr's comments in this thread? http://www.arcflashforum.com/viewtopic.php?f=2&t=4238&p=19329&hilit=overdutied#p19329
paulengr said:
Such currents are also unlikely to occur during an arcing fault (arc flash) so the real risk is during a dead short condition. I haven't found any original sources but there are plenty of statistics suggesting that these types of faults account for less than 10% of the faults that occur, and it would not occur during normal operation in the first place except...
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Davebones said:
Sq D did the study . They were the ones that said the breakers now weren't rated for the available fault current at the switchgear .
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I'd be inclined to have a third party do a study. I'm not saying there is a conflict of interest with Sq D doing it themselves, but a third party would take all the bias out of it.

I'm sure retrofitting Sq D gear of this size is astronomically priced, and a second study to confirm the results of the first would be money well spent.
 
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