Taps

[musa]

My question is I have an 800 amp 120/208v 3ph Wye service with an 800amp main breaker disconnect feeding 4-200amp MB subpanels being fed with seperate runs of 4-3/0 cu conductors & a #6grnd in 2" EMT, it is 32' to the last subpanel. My inspector is referring to article 240.21 (B)(2) as a failed inspection, I have tried to convince him that this scenario has nothing to do with the tap rule because I have overcurrent protection devices on both ends. I have the 800 amp Main breaker and the 4-200amp main breakers for the sub panels. Does anybody have a code reference that I can use to help me out?

 

[infinity]

How long are the #3/0's? Shouldn't be more than 10'. And the ground is too small also. Should be #1/0 for an 800 OCPD.

 

[infinity]

This is an addition to my first post which was somewhat truncated as I was side tracked by a yelling spouse. .

The inspector is correct. Your setup is a tap. The overcurrent device protecting the 200 amp conductors (#3/0) is 800 amps. That makes those conductors a tap. Taps conductors rated for 1/3 or more of the ampacity of the upstream OCPD are permitted in this application up to 25' in length. You need to provide OC protection for the #3/0 conductors. Also the EGC must be sized for the 800 amp OCPD ahead of the taps. According to 250.122 this would be a #1/0.

 

[Rich Elec.]

Trevor,
Help me understand this all correctly?
1. The tap conductors are too low of an amperage rating.
1/3 of 800 is 266.6.

Are the 200 amp panels now allowable?
Increase the wire size to 300mcm?

2. The tap conductors are too long. 25' max.
Which means that an OCPD must now be installed.

Disconnect at 25' max then feed a 200 amp panel?

3. Which code article tells you that the EGC must be sized for the 800 amp main?

 

[raider1]

There are three items you must comply with to use the 25' tap rule. First the ampacity of the tap conductors can't be less than 1/3 of the rating of the overcurrent device protecting the feeder. In this case the tap conductor would be 300 kcmil copper conductor at 75c or larger.

Second the tap conductors must terminate in a single circuit breaker or set of fuses that limits the load to the ampacity of the tap conductors. So if you terminate the 300 kcmil conductors in a 200 amp fues disconnect or breaker located so the tap conductors don't exceed 25' you are OK.

And third, the tap conductors must be protected from physical damage by being enclosed in an approved raceway or by other approved means.

250.122(G) requires that EGC's run with feeder taps shall not be smaller than shown in Table 250.122 based on the rating of the overcurrent device ahead of the feeder but shall not be required to be larger than the tap conducotrs.

Chris

 

[Pierre C Belarge]

Tap conductors do not come directly off of an overcurrent device. Tap conductors come off of conductors.
Do I understand this correctly as there are 3/0 conductors terminated directly to the 800 amp overcurrent device?

 

[iwire]

Do I understand this correctly as there are 3/0 conductors terminated directly to the 800 amp overcurrent device?

I am not sure that is a violation, a terminal is a type of conductor.

Also that would mean I could not terminate 3/0s directly into a 800 OCPD but I could run 4" of 800 amp conductor and start my 'tap' at that point. It just does not strike me as logical.

 

[infinity]

I am not sure that is a violation, a terminal is a type of conductor.

Also that would mean I could not terminate 3/0s directly into a 800 OCPD but I could run 4" of 800 amp conductor and start my 'tap' at that point. It just does not strike me as logical.

I agree, and I've seen it done this way many times in the field. The tap can originate at the lug on the switch or breaker as long a the correct lugs are used.

 

[jamesguy10]

I agree, and I've seen it done this way many times in the field. The tap can originate at the lug on the switch or breaker as long a the correct lugs are used.

Yup, as long as you have the right lugs its alright

 

[Pierre C Belarge]

240.21(B) Feeder Taps
Conductors shall be permitted to be tapped, without overcurrent portection at the tap, to a feeder as specified in...


In this section it is specifically referencing conductors/feeders, not termination of overcurrent devices.

And yes one could conceivably have a 400 amp overcurrent device, terminate 500 kcmil and install 100 feet of it, tapping at the location 100 feet away from the termination, as long as the tap at that location complies with the applicable section.

Think of motor feeders with multiple disconnects for smaller motors at a remote location from the distribution panel where the motors receive their supply.

 

[augie47]

taps

taps

Pierre,
I agree with you on the wording, but, out of couriousity, do you or does anyone you know enforce it that way. I can imagine requiring someone to add a section of wire and some means of tapping it (thus adding more connections) to avoid connecting directly the OCP device. (providing the correct lugs are used)

 

[eric stromberg]

240.21(B) Feeder Taps
Conductors shall be permitted to be tapped, without overcurrent portection at the tap, to a feeder as specified in...


In this section it is specifically referencing conductors/feeders, not termination of overcurrent devices.

Playing devil's advocate here, yes this section is referencing a feeder, which is defined as a conductor. But what is a conductor? Article 100 has three definitions for Conductor. Why couldn't the lugs on a transformer secondary be considered a "Conductor, Bare" as is described in Art. 100?

Often, in industry, a transformer secondary will feed multiple MCC's. For example, a 1 MVA transformer (1200 Amps at 480) will feed three MCC's. Each MCC will have 600 kcmil conductors triplexed, running to the secondary. The secondary lugs will have three 600's per phase bolted to the lugs. Is this a Code violation? All the conductors going to the MCC's are feeder taps.

 

[iwire]

In this section it is specifically referencing conductors/feeders, not termination of over current devices.

Again whos to say a terminal is not a conductor?

Take a look at the definition of feeder, the terminal itself could be considered a feeder. It says what it says, read it like you have never seen it before

And yes one could conceivably have a 400 amp over current device, terminate 500 kcmil and install 100 feet of it, tapping at the location 100 feet away from the termination, as long as the tap at that location complies with the applicable section.

100' or 1" either way we both seem to agree is compliant, so electrically is no safety advantage to not allowing the tap to start at the breaker terminal.

Lets say I have to do a tenant fit out where the provided power is supplied by a 600 amp breaker to that space.

Assuming this breaker has three barrel lugs my first thought might be to supply three 225 amp main breaker panels each supplied by 4/0s directly from the lugs of the breaker using the tap rules.

Edit: Pirre I am not trying to be PITA here I just don't see it as black and white as you laid it out.

 

[musa]

Taps

The inspector is still trying to say these are tap conductors. When I referred to the article 240.21(B) (that he specified) as saying the this is referencing Taps WITHOUT overcurrent protection he then tried saying that I had Service Conductors inside a building. Service conductors are generally from the point of the power company's transformer to the first means of disconnect, not the load side of a breaker. Does any one know of an article that I can use for reference

 

[raider1]

The term conductor does not always means a wire. The definition of conductor in webesters dictionary (and no this is not from the collegiate 11th edition ) is : a material or object that permits an electric current to flow easily.

So the terminals of a breaker are in fact a conductor as opposed to an insulator.

Chris

 

[Pierre C Belarge]

Again whos to say a terminal is not a conductor?

Take a look at the definition of feeder, the terminal itself could be considered a feeder. It says what it says, read it like you have never seen it before



100' or 1" either way we both seem to agree is compliant, so electrically is no safety advantage to not allowing the tap to start at the breaker terminal.

Lets say I have to do a tenant fit out where the provided power is supplied by a 600 amp breaker to that space.

Assuming this breaker has three barrel lugs my first thought might be to supply three 225 amp main breaker panels each supplied by 4/0s directly from the lugs of the breaker using the tap rules.

Edit: Pirre I am not trying to be PITA here I just don't see it as black and white as you laid it out.

I do not see any of the responses that are contrary to mine as being a PITA. I am always seeking some kind of clarification to issues I do not always have answers for...hence the collective minds of this site. Not that I always agree with some of the thought processes here :wink: thank God for a free country.

As with anyone else here, my ideas and thought processes have always been limited to the reading/contact with others mostly in my geographical area. So, sometimes I need a boot in the rear to straighten me out. Sometimes that boot has to be big and hard to shake loose long standing beliefs I have.


That being said. I understand that conductors are not limited to "wire".
My concern is that the "tapping" of the load side of a circuit breaker directly from the terminal of the CB with conductors smaller than rated for the CB rating (exclusive of such items such as motors, etc...) is a foreign process for me to digest.
As of this moment, I am not convinced that the tap rules of 240.21(B) permit the installation of the "tap" conductor(s) directly off of the CB terminal. Maybe someone can show me more INFO that will take me from the dark side...:grin:

 

[petersonra]

240.2
Tap Conductors. As used in this article, a tap conductor is
defined as a conductor, other than a service conductor, that
has overcurrent protection ahead of its point of supply that
exceeds the value permitted for similar conductors that are
protected as described elsewhere in 240.4.

A tap conductor is not defined by the conductor it taps to but rather by it being too small to be adequately protected by the upstream OCPD.

 

[infinity]

The inspector is still trying to say these are tap conductors. When I referred to the article 240.21(B) (that he specified) as saying the this is referencing Taps WITHOUT overcurrent protection he then tried saying that I had Service Conductors inside a building. Service conductors are generally from the point of the power company's transformer to the first means of disconnect, not the load side of a breaker. Does any one know of an article that I can use for reference

These are tap conductors and not service conductors. Ask him for the specific code references that you've violated. They should be from article 240 and 250.

 

[Filthy Phil]

Can some one give me a good definition of a tap?

 

[don_resqcapt19]

Tap Conductors. As used in this article, a tap conductor is defined as a conductor, other than a service conductor, that has overcurrent protection ahead of its point of supply that exceeds the value permitted for similar conductors that are protected as described elsewhere in 240.4.