Inspector problem

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Horst

Member
Location
Valrico, FL
I am working in a new jurisdiction and the inspector says this configuration is not code compliant (built to the engineers spec). This is a 400A CT service, the 2 parallel runs of 3 phase 4/0 AL come through the CT cabinet into a wire way and into 4 port polaris'. from the wireway there are 2 disconnects, 1 single phase, 1 three phase (both 200A NON FUSED) of course each of the phases are into the polaris, except "C" phase for the single phase panel is not used. (120/208v). This is on the exterior of the building. Directly behind each of the disconnects is a 200A panel (1 single, 1 three phase) and each has a 200A MB. His beef is that the "C" phase leg, only feeding the 3 phase panel is too small, since it is expected to carry up to 400A prior to the 200A OCP of the breaker. So, being the smart *** that I am, I asked if I could then simply install a 500 KCmil CU from the polaris to the lug on the 200A breaker in the 3 phase panel. He didn't buy that. He says the only solution is to fuse the disconnect outside. Am I missing something here? Thanks.
 
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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I don't understand the : "since it is expected to carry up to 400A prior to the 200A OCP of the breaker."
I would ask for some load calculations since you are using 180 amp conductors, but other than that I see no problem
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Why is the "C" phase different. A wire can be much larger than the load it serves.

If you add a disco outside on one then you would have to add a disco on the other but what is the difference if the disco is inside, as you have it, or outside, as he wants it. Does that change anything----NO.

Is there an ordinance that requires the disco outside? Sounds a bit bogus to me.

As Gus stated the only problem I see is if your load is calculated larger than 360 amps. 4/0 is good for 180 * 2 = 360
 

Horst

Member
Location
Valrico, FL
Disco's outside

Disco's outside

To clarify, there are 2 non fused discos on the outside next to the meter can being fed from a wireway where the 2 parallel runs terminate into polaris'. one is single pahse, the other 3 phase. "C" phase of course is missing a leg due to one of the discos being single phase.

From the discos, immediately behind through a block wall are the 200A MB panels with 200A MB. He has no problem with anything but the "C: phase leg being too small. I tried to explain to him that the 200A OCP at the MB on the interior panel protects the "C" leg. He does not get it.

Also, the calculated load is 285A (TOTAL).

I just thought I may be missing something, he insists that I change the 3 phase disco to a fused one to protect the "C" at 200A...

THOUGHT HE IS OUT THERE, So much for podunk jurisdictions...

Really wish I was wrong, would feel better about all the time and money I am going to spend to do his configuration...
 

bphgravity

Senior Member
Location
Florida
I don't have an issue with the wiring configuration, but do see some code issues with your description.

1. The service disconnecting means must have an integral service overcurrent device OR it must be immediately adjacent. You indicate the service overcurrent protection is located at an interior panelboard whereas the service disconnect is located outside.

2. Make sure your grounding and bonding configuration is correct. The conductors from the outside to the inside are FEEDERS thus you need an EGC run to each inside panel. Plus, the grounding must take place in the outdoor equipment.

Why do engineers and designers come up with such weird configuations? What's wrong with a simple, typcial, standard service?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Horst, welcome to the forum! :)


I believe you have a high-leg Delta. Otherwise, there's no reason to have a single-phase panel.

Regardless, tap rules alone permit your installation. What size are the rest of those conductors?
 

Horst

Member
Location
Valrico, FL
No high leg

No high leg

No, this is definitely 120/208. No high leg. The single phase panel is due to the engineer "value engineering the service" in other words a single phase panel is cheaper, and there are only a few three phase loads. Anyway, I spoke with the AHJ today, and he agreed that the configuration is legal based on the "immediately adjacent" precedent. The disconnects outside are non fused, but within a few feet of wire, the OCP is there and appropriate. Personnally, I would just have put 2 200A Fused disconnects to main lug panels inside. Not my call! Thanks for the support, I was really getting upset at this guy.
 
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