# 25 ft. Tap Rule



## RePhase277 (Feb 5, 2008)

I have been involved recently in a spirited discussion about an installation with a local inspector. I will say ahead of time that I won the argument and he capitulated.

*The situation*: I was contacted about replacing some services on apartment buildings after a recent tornado. The original services were 100 A, fed from a meter socket with #3 copper ran across the apartment, unfused, to a 100 A main breaker in the panel. Now the planned upgrade was to provide 200 A to each apartment with a new MLO panel an disconnect outside.

After getting the equipment up on the wall outside, I was told that budgetary constraints would necessitate that we keep the services 100 A. So the compromise was made that we leave a 200 A service on the wall and leave a 100 A main breaker panel inside 21 ft. away.

*The Problem:* Existing 1" conduit will not allow 3/0 copper conductors from 200 A service to 100 A main (not that they would fit the breaker anyway).

*My Solution: *Apply the 25 ft. Tap Rule. As far as I'm concerned, I feed #3 copper from the 200 A disconnect to the 100 A main in the panel. To me this satisfies the conditions of the tap rule. The #3 conductors are protected from overload by the 100 A main at the termination. Short circuit protection is provided by the 200 A breaker in the disconnect.

The inspector argued that it wasn't a tap until conductors of the "right" size were taken from the 200 A terminals, then tapped onto. I argued that the lugs of the 200 A breaker were just that: a tap from the unfused conductors of the line side. After a little code book jogging, he come to my side.

What do you guys think?


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## NolaTigaBait (Oct 19, 2008)

Yeah def. you are right. I think they have to be a minimum of 1/3 the ampacity of the 200...


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## garfield (Jul 30, 2009)

Is it 25 feet of wire or a lineal measurement?


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## brian john (Mar 11, 2007)

garfield said:


> Is it 25 feet of wire or a lineal measurement?


It is based on conductor length.

Are the 100 AMP OCPs in the same room as the taps?


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## RePhase277 (Feb 5, 2008)

brian john said:


> It is based on conductor length.
> 
> Are the 100 AMP OCPs in the same room as the taps?


 No. The 100 A mains are inside, while the 200 A service discos are outside.


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## Mike_586 (Mar 24, 2009)

garfield said:


> Is it 25 feet of wire or a lineal measurement?


Conductor length.


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## John Valdes (May 17, 2007)

I need to learn alot more about tap rules as I would have thought this was non compliant.
How can we land #3 cu to a 200 amp disconnect? I am asking?

I mean it this way. If I have a detached structure 10' away from the main structure and I wanted a 100 amp sub panel in the unattached structure, I could use a 200 amp breaker to feed the structure as long as I had a 100 amp main in the sub panel?

I understand I could reverse this and have the 100 amp breaker for the feeder and the 200 amp breaker as a switch in the structure. 
This is what I do not understand concerning the tap rule. I sure am glad this was brought up as I have no idea NOW.

Great to see you back Inphase!!!!!


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## Bob Badger (Apr 19, 2009)

InPhase277 said:


> What do you guys think?


I agree with your reading of it, there is no rule requiring that we start with 200 amp conductors.

The feeder tap can start at the breaker terminal, an unusal set up but in my opinion within code.


Now that said, is there an EGC run?

If there is a 'wire' EGC the size of that must be based on the 200 amp over current device.


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## RePhase277 (Feb 5, 2008)

John Valdes said:


> I mean it this way. If I have a detached structure 10' away from the main structure and I wanted a 100 amp sub panel in the unattached structure, I could use a 200 amp breaker to feed the structure as long as I had a 100 amp main in the sub panel?


The way I interpret the tap rules, yes. In your structure, the 10' tap rule applies and the setting of the overcurrent device could be 10 times the ampacity of the tap conductors. So you could land a #3 copper conductor on a 1000 A breaker so long as it terminates into a 100 A OCPD and is protected by a raceway.

Of course, I would never utilize such a setup in a residence outside of these government housing buildings where the residents themselves cannot work on the system.




> Great to see you back Inphase!!!!!


Thanks JV. Good to be back!


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## Bob Badger (Apr 19, 2009)

John Valdes said:


> How can we land #3 cu to a 200 amp disconnect? I am asking?



The key with the tap rules is all the details.

In this case he is using the 25' tap rule which requires;

The capacity of the tap is at least 1/3 the rating of the overcurrent device. He is set here


No more than 25' of conductor length. Which if you have to go up, over and down keeps things pretty close together. He is set here.


The tap must end in a breaker or fuses. He is set there.


It is in a raceway. He has that covered

The idea is this.

At 25 feet or less a ground-fault on those conductors will still trip the over current device fast enough to protect the conductors from over heating.

With the breaker or fuse in place at the end of the taps the conductors can not be over loaded.


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## frenchelectrican (Mar 15, 2007)

I have done like that quite few time as long the items what Bob highlighted and that will have no issue with the codes.

I know there are other taps rules we can able discuss as well.

There is a short verison IIRC under 15 feet and long one that should be unlimted { normally outdoor useage which I have used from time to time but very loosely }


Merci.
Marc


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## John Valdes (May 17, 2007)

Thanks guys. This has peaked my interest. Where should I start in the code book or other source to get up to speed. I may never need to use the tap rule, but I sure as hell want to know how? Thanks for the help Bob and Inphase.


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## Bob Badger (Apr 19, 2009)

John Valdes said:


> Thanks guys. This has peaked my interest. Where should I start in the code book or other source to get up to speed. I may never need to use the tap rule, but I sure as hell want to know how? Thanks for the help Bob and Inphase.


For the most part just take a look at 240.21, it is two or three NEC pages with each section covering a specific type of tap conductor.


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## John Valdes (May 17, 2007)

Bob Badger said:


> For the most part just take a look at 240.21, it is two or three NEC pages with each section covering a specific type of tap conductor.


Thanks Bob.


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## Wirenuting (Sep 12, 2010)

And what do you do when you have to repair a tap that's 30+ years old, wrapped in friction tape and has been burning split bolts on the 500 feeds for who knows how long, and you find a gaggle of wires, #12's included?
You fix it, report it, knowing it will still be waiting 2 years from now. 
Is a "tap" like this grandfathered in?


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