Circuit Breakers Required to be Below 48" for ADA Accessibility???

sparkyrick

Senior Member
Location
Appleton, Wi
Series rating will not matter if the available fault current doesn't exceed the SCCR of the breaker in question. If you can prove that rating is not exceeded you can play his game too. If it has been exceeded then I guess maybe the only real issue here may be his method of dealing with problems he does find.

If this guy really wants to keep his job for very long he has the wrong attitude. He may be the AHJ representative but he still serves the people he is inspecting for and not all of them are as stupid as he may think. Abuse of his "power" is one way to lose his job pretty quick.
He said I have 65K available at the the main on the Cutler Hammer meter stack. So now he wants another main installed inside with 65K rating in the Sq D panel too. If I had installed a Cutler Hammer Main Lug Only panel inside, he would have been happy. I questioned him why the House panel didn't have a main and his response was because it was Cutler Hammer.

Yeah, two inspectors in a city just south of me got the boot last year because of their abuse-of-power attitude. One was a building inspector and the other was an electrical inspector. Both working together to make people miserable.
 
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Is he giving you citations or just "I want"s? Can you hide behind something like "I'd change it, but the office need the code article to make the change and order the parts." Sounds like you need to go over this guy's head, to the county or state. If it's an engineered job, get the PE involved.
 

kwired

Electron manager
Location
NE Nebraska
He said I have 65K available at the the main on the Cutler Hammer meter stack. So now he wants another main installed inside with 65K rating in the Sq D panel too. If I had installed a Cutler Hammer Main Lug Only panel inside, he would have been happy. I questioned him why the House panel didn't have a main and his response was because it was Cutler Hammer.

Yeah, two inspectors in a city just south of me got the boot last year because of their abuse-of-power attitude. One was a building inspector and the other was an electrical inspector. Both working together to make people miserable.
How far away and what size conductors are supplying the inside panel? Is it in magnetic raceway? Is there motors supplied that will contribute to fault current? The answer to those questions will impact how much fault current is available at the end of that circuit.
 

sparkyrick

Senior Member
Location
Appleton, Wi
How far away and what size conductors are supplying the inside panel? Is it in magnetic raceway? Is there motors supplied that will contribute to fault current? The answer to those questions will impact how much fault current is available at the end of that circuit.
25' run of 250Kcmil Al in PVC.

Two RTU's at 25A MCA/45 MOCD, not sure of the HP rating of the compressors though.
Two 1.5HP 3? vacuum pumps on freq drives, 1? input, the drive creates the third leg.
One 1.5HP 1? air compressor.
One typical laundry washing machine.
One typical laundry dryer.
One 1/4HP grinder.
One 1/2HP garbage disposal.
Six FHP exhaust fans (bathroom style exhaust fans)
One full size refrigerator.
One dorm room size refrigerator.

Thats all the motors I can think of.

65K available at the service and I have no clue how to figure fault current.
 

sparkyrick

Senior Member
Location
Appleton, Wi
Is he giving you citations or just "I want"s? Can you hide behind something like "I'd change it, but the office need the code article to make the change and order the parts." Sounds like you need to go over this guy's head, to the county or state. If it's an engineered job, get the PE involved.
I sent an email to the state inspector and I'm waiting for a reply. I didn't question him on the mix and match between manufactures because I didn't know for sure myself. If I know I'm right on something, I'll ask for a code reference, that usually stops the "I wants".
 

kwired

Electron manager
Location
NE Nebraska
25' run of 250Kcmil Al in PVC.

Two RTU's at 25A MCA/45 MOCD, not sure of the HP rating of the compressors though.
Two 1.5HP 3? vacuum pumps on freq drives, 1? input, the drive creates the third leg.
One 1.5HP 1? air compressor.
One typical laundry washing machine.
One typical laundry dryer.
One 1/4HP grinder.
One 1/2HP garbage disposal.
Six FHP exhaust fans (bathroom style exhaust fans)
One full size refrigerator.
One dorm room size refrigerator.

Thats all the motors I can think of.

65K available at the service and I have no clue how to figure fault current.
How did inspector know there was 65K available at service? Just because it maybe had 65K rating doesn't mean that is what is available.

A quick check at a chart in the American Electricians Handbook shows 55.6kA available at transformer terminals of a 250kVA, 3.01% impedance, 120/240 single phase transformer (largest single phase transformer in the chart) 25 feet away with parallel 350 aluminum (largest conductors in the chart) drops it to about 35K.

My point is available fault current drops pretty fast when you factor in conductor sizes and lengths, but you still need to give them a look as relatively short distances will catch you off guard and require higher interrupting rated equipment.

25 feet of conductor from a transformer to a meter pack is usually pretty easy to have, you already take up nearly half that length in vertical portions of raceway in many cases and just how often is a transformer any closer than 10-15 feet horizontally from the service equipment?
 
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sparkyrick

Senior Member
Location
Appleton, Wi
How did inspector know there was 65K available at service? Just because it maybe had 65K rating doesn't mean that is what is available.
The building was recently constructed over the winter, so he had knowledge about the service and available fault current from the POCO's transformer (which is three phase) and the available fault current at the meter stack. He called it a 900A, 120/208V service. 400 for the restaurant that built the building, two 200A for future tenants and a 100A house panel.
 
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kwired

Electron manager
Location
NE Nebraska
The building was recently constructed over the winter, so he had knowledge about the service and available fault current from the POCO's transformer, which is three ? by the way.
Ok. Is 65k the actual available current or is it the rating of the main device(es)? If standard devices go from 42 to 65k we really don't know what we have if going by the device rating only. Chances are it is at least 42k if a 65k device was selected.

Now add your 25 foot feeder to your new equipment and you could possibly be in the 22k range being acceptable devices to use, but probably worst case only need a 42k rated device. If you are close, adding more length to the feeder is possibly a simple solution.
 

sparkyrick

Senior Member
Location
Appleton, Wi
Ok. Is 65k the actual available current or is it the rating of the main device(es)? If standard devices go from 42 to 65k we really don't know what we have if going by the device rating only. Chances are it is at least 42k if a 65k device was selected.

Now add your 25 foot feeder to your new equipment and you could possibly be in the 22k range being acceptable devices to use, but probably worst case only need a 42k rated device. If you are close, adding more length to the feeder is possibly a simple solution.
He said 65K available at the 200 meter stack breaker I was using. The service equipment is rated 100K.
 

kwired

Electron manager
Location
NE Nebraska
Yes.

I'm starting to wonder if we should contact the POCO and verify what he is telling us.
A quick ball park figure can be made if you know the transformer KVA rating, conductor size, type and number of parallel runs and even closer if you know exact transformer impedance, but that info is likely inside the access covers. What would be unknown is losses on the primary, most of these simpler calculations assume infinite available primary current, but they leave you on the high side with results instead of the low side.
 

sparkyrick

Senior Member
Location
Appleton, Wi
A quick ball park figure can be made if you know the transformer KVA rating, conductor size, type and number of parallel runs and even closer if you know exact transformer impedance, but that info is likely inside the access covers. What would be unknown is losses on the primary, most of these simpler calculations assume infinite available primary current, but they leave you on the high side with results instead of the low side.
Monday, I could tell you the KVA rating of the transformer and number of wires, but not the wire size. From the transformer, the wires terminate in a tap box between the two services and that tap box is sealed by the POCO.
 

kwired

Electron manager
Location
NE Nebraska
Another quick look at tables in American Electricians Handbook seems to indicate you will not even be close to needing 65K rated equipment if the supply transformer is not at least a 750kVA and more likely at least a 1000kVA unit.

Line to line available fault current of a 1000kVA, 5.32% impedance unit at distance of zero feet is 56787 amps.

Line to neutral will be higher at close distances but eventually line to line becomes the higher value. Just 25 feet can make a big difference here.

So I would say that if your transformer is any smaller than 750kVA your inspector is just trying to be a PITA, more than he is trying to help you comply with codes.
 

kwired

Electron manager
Location
NE Nebraska
Monday, I could tell you the KVA rating of the transformer and number of wires, but not the wire size. From the transformer, the wires terminate in a tap box between the two services and that tap box is sealed by the POCO.
Also adding more distance and lowering the available current at the other end.
 

kwired

Electron manager
Location
NE Nebraska
From the transformer to the service is around 65', but thats a guess. I'd have to measure on Monday.
What I was getting after was the fact that the presence of the tap box likely means even more distance between the transformer and service equipment, or even a reduction in conductor size after the tap box, all adding to the conductor impedance and lowering the available current at the service equipment.
 

sparkyrick

Senior Member
Location
Appleton, Wi
Anyone care to figure the fault current for me.
208/120 75KVA 3 phase POCO transformer, 3.6% impedance.
3 parallel runs of 350Kcmil Al, 68' tansformer to tap box on service.
 
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