25' tap rule inspection failure

[kameele]

For a fun-filled Friday afternoon, i have just been informed that my very carefully measured (on paper :roll: ) 25' tap will likely end up being 26-27' long and the inspector didn't go for it. nothing can change location, so I'm looking for options.

a little background: we are replacing a 2000A MCC and adding a separate 1000A MCC to a plant. Both will be fed from a 3000A breaker on the secondary of the plant transformer. the feeder to the 2000A MCC would not be considered a tap becasue it is rated at the full 3000A. Each one has a main breaker. we need to keep them separately isolatable because the 1000A one will be supporting necessary plant functions while we rip out and replace the old 2000A one.

i have a suggestion that we put another breaker/fused switch in between the main breaker and the new 1000A MCC. It seems like it will satisfy code but look like a kluge and cost more than I would like.

I'm up for any expert opinions you care to offer (and one or three beers)

thanks,

 

[augie47]

concrete encase it and call it an outside feeder

 

[mxslick]

Good one Augie.

Seriously, 26-27 feet and a red tag? :roll: I know the Code says 25', but what is the hazard from the extra 2 feet? Any testing or lab results PROVE that the resistance (or exposure) of that extra 2 feet is creating a hazard?

IMHO adding a disconnect, breaker or fuses to this ADDS additional connections and possible failure points (or arc flash hazard potential) greater than the extra 2 feet of conductor would.

If I were the inspector in this case, as long as it was properly installed and protected from physical damage I would have passed it.

 

[iwire]

I am not 100% sure that concrete encasing it would make it fully compliant. Safe yes, compliant ... not so sure. I think they would have to start outside.

Is there any way to change the raceway in a way that shortens things up?

Like change from pipe to wireway eliminating wasted length used in sweeps?

Or run the conduits 'as the crow flies' instead of parallel with the building?

I did a 1600 amp tap off of a 4000 amp service and had the same issue, we had to run the four conduits at a diagonal to just stay under 25'

 

[Smart $]

concrete encase it and call it an outside feeder

Regarding outside feeders, a couple questions for kameele:

How much of the existing tap run is inside? ...outside?​

Please describe in terms of 240.21(B)(5) Outside Taps of Unlimited Length.

Aside from that, to keep the feeders isolated, you must either unland the 2000A MCC feeders from the 3000A Main, or install a separate breaker for the 1000A MCC feeders thereby removing the tap condition from the equation.

 

[infinity]

Can you add a few more sets of conductors to eliminate the tap rule altogether?

 

[danickstr]

Run it outside, encase it in concrete, then bring it back inside.

 

[Strife]

Yeah, I got red tagged on a 24-1/2" receptacle from the edge of the counter. Not as costly as the OP, but yeah, the law is the law. technically you can get pulled over going half a mile over the speed limit and it's not much you should be able to do about it.
Well, not red tagged, but failed inspection.

Good one Augie.

Seriously, 26-27 feet and a red tag? :roll: I know the Code says 25', but what is the hazard from the extra 2 feet? Any testing or lab results PROVE that the resistance (or exposure) of that extra 2 feet is creating a hazard?

IMHO adding a disconnect, breaker or fuses to this ADDS additional connections and possible failure points (or arc flash hazard potential) greater than the extra 2 feet of conductor would.

If I were the inspector in this case, as long as it was properly installed and protected from physical damage I would have passed it.

 

[iwire]

Can you add a few more sets of conductors to eliminate the tap rule altogether?

I was thinking that as well but 3000 amps of conductors landing in 1000 amp gear is going to be tough.

 

[kameele]

Thanks for the input so far. Outside tap was my first thought, but since it's running in in existing overhead wireway, the concrete encasing becomes a little problematic The AHJ hasn't officially failed it yet, but has expressed his concern. I'm going to site on Monday to see if we can work something out that doesn't involve an extra breaker (1200A is NOT going to be cheap). Another interesting twist to this would be that the plant manager is OCD and if we were to angle some pipe, it would drive him absolutely bonkers.

I haven't met the inspector in person, but my field manager says he's been reasonable about earlier inspections. We can't move the gear, but maybe we can put in three conduits and cut down the distance if there's no room for negotiations.

 

[wireguru]

can you stick a box a couple feet into the conduit run with junction blocks in it, and run 3000 amps of wire between the service and the box to keep the length of the 1000 amp conductors under 25ft? (i have no idea if this is legal or not)

 

[augie47]

Hopefully the inspector will be lenient. If not, I think wireguru has the best idea..increase the conductors from the breaker to 3000 amp capacity for the 1st few feet, then tap your feeder to those.

 

[kameele]

Thanks for that. It sounds somewhat painful to do, but a lot less expensive than the CB/Fuses that we were thinking of. Hope the inspector had a good weekend and is feeling generous.

 

[kameele]

I'm now on site and after talking it over with my electrician, we think that the terminals and full capacity feed will be the best solution. right now, I'm looking to find some terminals/distribution blocks that will handle 8-500s on the line side and 10-500s on the load (3 for the 1000A and 7 for the 2000A) So far, the biggest I have come up with is 760A, but it appears that I would need one for each conductor and that would lead to a rather large box. I haven't had to deal with connectors for this large current, so suggestions again are wlecome.

 

[mxslick]

Before you go through all that expense and effort, have the inspector take a look at it and see if he'll let the extra foot or so pass...I really think that unless your EC has made that inspector mad he'll be reasonable and allow it to pass as-is.

EDIT: Re-read the OP and see that inspector has already said no, but I would still plead my case and point out that adding terminals, or any device adds potential failure points that the continuous feeder wouldn't have.

One thing not clear: Has the inspector actually been on-site to see this, or was his "no" done by phone? Perhaps an on-site visit would persuade him that it would be ok as-is?

I reiterate from my last post that I seriously doubt that the extra foot or so presents a hazard.

Why are people so afraid to ask first? The worst-case is that you will have to make changes..and maybe the inspector has a better suggestion.

 

[iwire]

Asking the inspector to ignore the code is really out of line.

 

[jwjrw]

Asking the inspector to ignore the code is really out of line.

I agree. It is his butt on the line. However if he looked at it and approved it I would be happy but I wouldn't point out that " this tap is really 28 feet thanks for overlooking it".

 

[iwire]

I agree. It is his butt on the line. However if he looked at it and approved it I would be happy but I wouldn't point out that " this tap is really 28 feet thanks for overlooking it".

Yes, exactly.