What would U Do?

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Dennis Alwon

Dennis Alwon

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Chapel Hill, NC
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Retired Electrical Contractor
I am bidding a small retail office that requires a 120/208 Square D I-Line 200 amp 3 phase breaker with a 56K AIC rating.

I got a price of $1550.00 new and $868.00 Refurbished. First question is

1) WWUD? What would you do?
2) Are the used one worth a damn--- one year warranty.
3) Are you required to use a new one--- plans don't stipulate.
My gut is go with the new, esp. since this is a brand new building. For bidding sake I would definite use new price but if they wanted to cut money out- if I get that far-I can make this an option. Would this be a safe thing to do or am I looking for trouble?
 
56Kaic

56Kaic

56Kaic? on a 208/120V-3ph panelboard what is this fed from? Is this correct? you will have to install 65Kaic seems like it could be overkill..
 
I am not a gambler. All I can think of is what if it does malfunction and causes an outage? What kind of monetary damages would the customer suffer due to an outage and who would they be looking to for recovery?

We recently bought a large cooler of meat due to just a small outage.:roll: (A single small switch was left off)
 
Mike01 said:
56Kaic? on a 208/120V-3ph panelboard what is this fed from? Is this correct? you will have to install 65Kaic seems like it could be overkill..
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Poco told me teh aic of the trany was 52,000 but probably a bit lower. The aic for those breakers go from 25K to the next one at 65K. Even if the engineer was a bit high it would still take a 65k rated breaker.

I have no idea what the feed is from. The building is 10 stories with apartments (condos) and retail shops. The retails shops are fed with a 1600 amp service I believe.
 
If it were my building I would be very upset with used equipment being installed in a new building. I would specify in my quote that I am not using refurbished equipment. JMO.
 
Dennis Alwon said:
I got a price of $1550.00 new and $868.00 Refurbished.

My gut is go with the new, esp. since this is a brand new building.

For bidding sake I would definite use new price but if they wanted to cut money out- if I get that far-I can make this an option.
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For new construction, I'd recommend new. $700-ish isn't enough to risk it.

If the job was to replace an existing breaker, I'd offer the choice up front.
 
Dennis Alwon said:
Poco told me teh aic of the trany was 52,000 but probably a bit lower. The aic for those breakers go from 25K to the next one at 65K. Even if the engineer was a bit high it would still take a 65k rated breaker.
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Maybe, maybe not. The available current at the breaker will be nowhere near that at the transformer, unless they're very close.

Each section of wire, some terminations, devices, etc., contribute to lowering the requirement by the time it gets to the breaker.

You should do a fault-current study, or whatever it's called. You'll need to know the size and length of each conductor segment.

Please forgive me if you already know this stuff. :)
 
LarryFine said:
Maybe, maybe not. The available current at the breaker will be nowhere near that at the transformer, unless they're very close.

Each section of wire, some terminations, devices, etc., contribute to lowering the requirement by the time it gets to the breaker.

You should do a fault-current study, or whatever it's called. You'll need to know the size and length of each conductor segment.

Please forgive me if you already know this stuff. :)
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Thanks. I do not know how to do a fault current calculation. I hear it is pretty involved. He told me the parallel wires sizes, how many and the distance but I didn't pay him no nevermind.

Do you really think it could be under 25K??
 
Dennis Alwon said:
Do you really think it could be under 25K??
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Yes. I've done them myself. I searched for and found a "free fault current calc" a few years ago.

I just did that and found a free one on this site. :)

The POCO field engineer should provide the numbers to the point of service, where they're conductors and yours meet.
 
I rather dought that the contract would not call for new. If it didn't then you could sumit it both ways.This sounds like major building i think new is only way to go
 
I would see if you could find a "new/used'', for lack of a better way to name it, there are many times we have ordered new panels with the breakers installed, then the requirements change. We wind up with never energized breakers, but they are technically "used" because they have been installed. Your post is about a month late, because I recently sold two of the exact breaker you are talking about. It was new in the gear and never used. Sorry timing is everything.
 
I tend to agree with Larry. You may get down to 22K, but if not I would guess that a breaker like that may already be rated at 65K/42K/22K and not be that special.

If they are paying for it I would go new and not give them a choice.
 
Okay I have done a calculation based on all the info needed and I am still at 41k.

So I need understanding of some issues and I apologize for my ignorance as I never dealt with this before.

The fault current calculator has 2 calculations, One is the fault current at the main disconnects for L-L at 41k and the other is L-N at 32K. Which one do I use???? I assume the higher?????

Also what does this all mean. I was told that if I had a breaker that had an aic rating higher than the fault current from the poco that I would not need to worry about the branch circuits downstream. The breaker feeds the MLO panel in the retail space. Then I had an inspector say that that was not true. He said all breakers had to be 56K???? I didn't even know they made 56K branch circuits for 120V panelboards. I thought they were all 10K.

The engineers also state that series rating is permissible. What does this mean.

Basically I need to know what I am required to do here. :-?:-? Totally.

The distribution panel is a Sq. D HCP model.
 
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