Resi Main AIC

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chris kennedy

Senior Member
I'm bidding a couple hundred cake service changes. The same can is still available and company owner wants it bid to use the old main in the new can.

Existing main is 150A 10,000AIC. Is 10,000 typical for resi? Thought is was 22k.

View attachment 1747
 

mdshunk

Senior Member
10K is all we've ever needed here most of the time, but I see a lot of the equipment now is 22K anyhow.
 

480sparky

Senior Member
Older stuff is typically 10K. Newer is rated 22K. You may not me able to use the breakers. Contact your utility to see what the fault current is on their transformers.
 

chris kennedy

Senior Member
480sparky said:
Contact your utility to see what the fault current is on their transformers.
Thats what I figured but thought one of you people might say:

'Your an idiot Chris, typical resi trannys can't deliver over 10k.'
I only went to look at this because it was on my way home.
 

frizbeedog

Senior Member
chris kennedy said:
Existing main is 150A 10,000AIC. Is 10,000 typical for resi? Thought is was 22k.
Local Power Company here has recently changed their requirements for residential AIC to require 22k for up to 400amps.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
chris kennedy said:
The same can is still available and company owner wants it bid to use the old main in the new can.
Gee, what's wrong with the old can? It looks like it's equipped to drain.
 

charlie

Senior Member
frizbeedog said:
Local Power Company here has recently changed their requirements for residential AIC to require 22k for up to 400amps.
HMMM. The serving electric utility usually stops at the service point. Most electric utilities, will just give you the expected worst case available fault current and leave it up to you to determine what is needed for the AIC rating. With smaller transformers and up to 50 kVA, you will not have enough available fault current to need more than 10 kAIC rating unless the service is a large underground fed one and the transformer is on the nose of the service equipment. :smile:
 

frizbeedog

Senior Member
charlie said:
HMMM. The serving electric utility usually stops at the service point. Most electric utilities, will just give you the expected worst case available fault current and leave it up to you to determine what is needed for the AIC rating. With smaller transformers and up to 50 kVA, you will not have enough available fault current to need more than 10 kAIC rating unless the service is a large underground fed one and the transformer is on the nose of the service equipment. :smile:

From thier "Electric Service Requirements" Manual

1.5.2 Single Family Residential (201 to 400 Amps)
For single family residences with services in the range of 200 to 400 amps,
the Customer is responsible for furnishing equipment that will withstand a
maximum 22,000 amps fault current. For services larger than 400 amps,
PGE will provide the maximum available fault current to the Customer upon
request.

Originally I posted that it was for up to 400 amps, but it is for 201 to 400 amps.
I provided a link for you to entertain your confusion. I haven't asked for an explaination, it was new this year. They must have thier reasons.

Electric Service Requirements. See chapter 1
 

charlie

Senior Member
frizbeedog said:
They must have their reasons.
I am guessing that their reason is to make sure that they are not liable for someone selecting the wrong AIC equipment and to keep from putting together any charts that would show what their maximum available is for their various sizes of transformers. In other words, I believe that they are lazy and are afraid of a lawsuit. :)
 

chris kennedy

Senior Member
charlie said:
With smaller transformers and up to 50 kVA, you will not have enough available fault current to need more than 10 kAIC rating unless the service is a large underground fed one and the transformer is on the nose of the service equipment. :smile:
I will call POCO Monday as I looked at a couple of the 20 year old pad mounts and the name plates are gone. These trannys feed 4 units each so from what you describe sounds like 10k is OK.

Of topic but an update. Still no POCO lock on the vault as of yesterday. Going on a month now. Thats how FPL rolls.
 

CopperTone

Senior Member
I hate reusing old stuff - why not just install all new mains? If they fail - they'll blame the EC - if you break it during disassembly, you would be blamed and on the hook to replace it - if it doesn't work after you reinstall it - even though you didn't do anything wrong you'll get blamed - you'll get blamed for anything for the next year - don't use old crap. Plus, you drive down the price on the job, and when a company who believes in doing things right bids the job - they lose it to companies that are piecing the job together.
I know I'm not in this business to help out the guy who needs a lot of work done cheaply. I do lose bids to guys who cut corners and the people who are comparing the bids aren't looking at the same job - apples and oranges - but all they see is the price and think they are getting the same job for a lot less money. Why do most of the job right? Heck, why not just buy some sheet metal and repair the rusted out cabinet - that would save the owner a ton of money - and you'll be out of there in no time.

BTW - I have a saying - If money is a problem, come back when it's not!
 
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mdshunk

Senior Member
CopperTone said:
I hate reusing old stuff - why not just install all new mains?
The owner specifically wants to reuse the old mains. That's certainly his right. I take certain offense to the suggestion that reusing any part of the old service is not "doing the job right". I'm going to go out on a limb here and guess that you are not a business owner.
 

CopperTone

Senior Member
I'm not looking to get into a pissing match here. I do own my company - and for long enough to see down the road at potential problems, problems I'd rather not open my company up to. Sure, it's the owners right to reuse old stuff, I see it as my right to show the owner how to do the job right the first time. I can see the point that reusing old stuff isn't necessarily the "wrong way" but it certainly isn't the best way. You can take all the offense you want or look at it as possibly advice. best of luck either way.

Sometimes you have to learn the hard way to learn something at all.
 

mdshunk

Senior Member
CopperTone said:
Sometimes you have to learn the hard way to learn something at all.
...and sometimes you need to quit thinking like an ar-teist and think more like a businessman.
 

CopperTone

Senior Member
I am just glad that you don't work for me. You'd cost me too much money eventually. Hows that for business thinking?
 

mdshunk

Senior Member
CopperTone said:
I am just glad that you don't work for me. You'd cost me too much money eventually. Hows that for business thinking?
Why? Would you go back and replace a bunch of main breakers for free? I think not. Truth be told, I give "good", "better" and "best" options on small estimates like this, so they'd have their choice.

I am constantly puzzled by guys that won't do a job at all if they can't do it their way. A small slice of the pie is better than no pie at all. The profit is still the same. Matter of fact, the profit potential is probably greater on just replacing the cans alone in this case.
 
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