Any issues with this installation?

[George Stolz]

I'm glad you guys know what's going on, 'cause I've read this probably four times over the course of the day and I still can't visualize the installation.

So whatever Mike says, I'll agree with.

 

[bjp_ne_elec]

The conductors are copper with #6 AWG THHN. I'm going to see if I can post a graphical, as I see George is having trouble visualizing. I may need some help in posting graphics. In that drill bit discussion, Larry Fine postes a nice graphical representation of some points he wanted to make about the challagne of drilling in to old work situations.

Larry - did you do that in something like Power Point? And then what is that process to get it to post?

Smart$ - you say they are tap conductors - so is the original installation (the #6 AWG THHN essentially protected by the 100A Main Breaker in the main panel) legal, as it was orginally installed?

Thanks,

Brett

 

[antenna2001]

Panel Classification

Panel Classification

"...If the tap panel has a neutral (grounded conductor) it is a lighting and appliance panel"

I thought panel classification was based on percentage of circuits served, per 408.34(A) and 408.34(B). Branch circuit classification, however, is based on whether or not the branch circuit has a connection to the neutral, per 408.34.
Am I wrong?

 

[bjp_ne_elec]

Here's my attempt of graphically displaying the situation, and also my first attempt at uploading. I drew it up in Power Point and saved as a jpeg file.

Please note that I didn't include the Neutral and Grounding Electrode Conductor and EGC in my sketch, as I figured it get too busy. The neutral is isolated from the ground in the subpanel, but is bonded together in the main panel. The ground between the subpanel in the original installation is the rigid metal nipple between the two panels - there is not seperate EGC installed.

Thanks,

Brett

 

[jwelectric]

Brett;

There is a problem with these conductors being ?tap conductors?.

As you have outlined these conductors are less than 10 feet in length and land on the lugs of a main lug panel. Look at 240.21(B)(1)(1)(b) and you will see that these conductors are required to;

b. Not less than the rating of the device supplied by the tap conductors or not less than the rating of the overcurrent-protective device at the termination of the tap conductors.

Let?s say for the sake of argument that this sub panel is a 60 amp panel and is supplied with a number 6 conductor. Now we have a problem with 408.36(A) and exception 1 of that section.

Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.

As outlined here the sub panel must have Overcurrent protection that is not greater than the panel therefore the 100 amp main breaker protecting the #6 will be a violation of this section.
The conductors coming from the lugs in the main panel going to the lugs of the sub panel will be required to be sized at 100 amps for this installation to comply. This will require the sub panel to be rated at 100 amps also.

As you have posted this scenario there is no way to make this installation code compliant short of changing the way it is set up now.
If you want to leave the main panel in place the 100 amp main breaker will need to be anchored to the panel as outlined in 408.36(F).
The feeders and sub panel will be required to be rated at 100 amps as outlined in 408.36(A) and 240.21(B)
Or
Set a breaker that will supply the sub panel and size the feeder conductors based on the size of the breaker.

 

[bjp_ne_elec]

jwelectric - I fully agree. I've never said I believe the installation, as it sets presently ( I have convinced the customr that a new 12 circuit subpanel is the right thing to do), is compliant - I'm just trying to get everything clear in my mind when it comes to subpanels and taps. I've always been a little confused in the tap rule - and get the impression others are as well.

Thanks,

Brett

 

[jwelectric]

To help you better understand the sub panel and taps you will need to read and study sections, 240.21 and 408.

408.36 clearly states that a lighting and appliance panelboard is to be protected at not more than the rating of the panel. This will rule out any thoughts of using a main lug panel and tap conductors together.

 

[Smart $]

Smart$ - you say they are tap conductors - so is the original installation (the #6 AWG THHN essentially protected by the 100A Main Breaker in the main panel) legal, as it was orginally installed?

First off, quit saying the #6's are protected by the 100A Main OCPD. Its simply a false statement. Tap conductors are protected on their load side and the reason for distance restrictions.

I can't say for certain these tap conductors are compliant without more information:

1) What is the maximum ampere rating of the subpanel.
2) What is the load, calculated or actual, whichever is greater, of the circuits served by the subpanel.

For tha sake of discussion, let's say the subpanel is rated at 60A. This would be a borderline situation with #6 thhn conductors. The terminals would have to be rated 75? to allow the #6's to have an capacity of 65A. The subpanel would then have a rating less than the ampacity of the tap conductors and therefore the tap conductors would be compliant on this point of criteria. If the terminals are rated 60?, the subpanel would be rated higher than the 55A adjusted capacity of the tap conductors and therefore the tap conductors would be non-compliant on this point of criteria. However, if the panel is rated 55A or less the tap conductors would be compliant on this point of criteria regardless of the terminal temperature ratings.

If compliant to this point, the load requirement must also be met. A quick guess would be the sum of the cb's trip ratings. If the sum is equal to or less than the rating of the panel [and operating properly, and not tripping], the tap conductors would be compliant on this point of criteria. If the sum exceeds the rating of the panel, the only way to be certain is by calculating the load in amperes and determining the actual draw of the loads served. The greater value of the two must be less than the panel's maximum ampere rating.

 

[jwelectric]

Smart;

Using your thoughts how would you get around 408.36?

If the number 6 was landing on a 60 amp breaker I would agree with what you are saying but Brett has already said that the sub panel is a main lug panel.
This would then have a 100 amp breaker protecting the sub panel. This would require the sub panel to be rated at 100 amps and thus requiring the feeders to be rated at 100 amps.

Let?s don?t forget that the requirements of 240.21 is not all that is to be considered in this installation.

 

[Smart $]

...
Let’s say for the sake of argument that this sub panel is a 60 amp panel and is supplied with a number 6 conductor. Now we have a problem with 408.36(A) and exception 1 of that section.

Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.

Yes, but the protection of tap conductors are on the load side, therefore the panel and load are the panel's feeder protection...

[edited to add] I must say this is stretching tap rules to the limit, but the code is "black and white"

 

[Smart $]

See P#30.....

 

[jwelectric]

I agree with this statement, BUT, we have another section that forbids this installation. What are we to do with 408.36?

408.36 Overcurrent Protection.
(A) Lighting and Appliance Branch-Circuit Panelboard Individually Protected. Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.

Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.

408.36 states that there must be a main

Exception one states that this main can be left out if the feeder has Overcurrent protection not greater than the sub panel.
In this case the feeders are protected at 100 amps even though they are tapped from the main panel. There is no Overcurrent (main) in the sub panel.

 

[Smart $]

...
Exception one states that this main can be left out if the feeder has Overcurrent protection not greater than the sub panel.
...

It does not state where the overcurrent protection has to be or the means by which overcurrent protection is accomplished. The feeders in this case are also tap conductors. Tap conductors require overcurrent protection. If these tap conductors are protected so is the feeder for the panel, as they are one and the same.

In this case the feeders are protected at 100 amps even though they are tapped from the main panel. There is no Overcurrent (main) in the sub panel.

No, no, no. Your making the same basic error as Brett (was?). You're thinking overcurrent protection only occurs through the main ocpd.

 

[George Stolz]

Brett, thanks for the picture.

If the number 6 was landing on a 60 amp breaker I would agree with what you are saying but Brett has already said that the sub panel is a main lug panel.

This would then have a 100 amp breaker protecting the sub panel.

This is the key.

The conductors are not being protected at their load side. They are therefore not tap conductors. They are simply conductors installed with improper overcurrent protection at their source of supply.

240.21(B)(1)(1)(b) is what prohibits this installation.

No, no, no. Your making the same basic error as Brett (was?). You're thinking overcurrent protection only occurs through the main ocpd.

How is that an error? What is the "protection" at the load end of the conductors? The lugs are not protecting anything.

240.21(B)(1) Where the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:
(1) The ampacity of the tap conductors is
(b). Not less than the rating of the device supplied by
the tap conductors or not less than the rating of the
overcurrent-protective device at the termination of
the tap conductors.

Looking at Brett's diagram (and reading the following posts) it seems you're saying that all the branch circuit OCPD's can serve as the protection for the tap. I don't see anything codewise to support that claim.

 

[jwelectric]

No, no, no. Your making the same basic error as Brett (was?). You're thinking overcurrent protection only occurs through the main ocpd.

Well let?s look at it one step at a time.

Let?s start with the tap rule
(B) Feeder Taps. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (B)(5). The provisions of 240.4(B) shall not be permitted for tap conductors.
We can tap what? The feeder

Now let?s look at 409.36 exception 1
Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.
If what has protection? The feeder

You are trying to use the Overcurrent protection for a tap rule to fulfill the requirement for the required feeder protection. The two are different.

Does the feeder being tapped have Overcurrent protection? The feeder Overcurrent is what would protect the tap in the event of a ground fault or short circuit and the Overcurrent device that the tap is terminated with protects it from Overcurrent.
Protection as outlined in 240.21 is to protect a tap not the feeder that supplies the tap.

The requirement in the exception of 408.36(A) is requiring that the FEDDER be protected not greater than the panel board. This rule kills the Overcurrent requirement of the tap rule in 240.21.
Being that the FEEDER (not the tap) is protected at 100 amps then the sub panel wired as it is would be required to be at least 100 amps.

Going back to the tap rule now
(B) (1) Taps Not Over 3 m (10 ft) Long. Where the length of the tap conductors does not exceed 3 m (10 ft) and the tap conductors comply with all of the following:
(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the circuits supplied by the tap conductors, and
b. Not less than the rating of the device supplied by the tap conductors or not less than the rating of the overcurrent-protective device at the termination of the tap conductors.
Here we see that the ampacity of the conductor must be the same as the ampere rating of the terminations (B)(1)b. Now the tap conductors are required to be rated 100 amps.


The way the panels are now wired is a violation of 408.36(A) and 240.21(B)(1) as well as 408.36(F) and this is how I would write it up on a noncompliance report.

 

[Smart $]

Let?s start with the tap rule
(B) Feeder Taps. Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (B)(5). The provisions of 240.4(B) shall not be permitted for tap conductors.
We can tap what? The feeder

The comprehension of this provision actually starts at 368.17(C), which addresses requirements of feeder and branch circuit tapping of a busway?the busbars in the discussion's main panel. In summation it requires an OCPD at the tapping of the busway. However, it goes on to the following ? Exception No. 1: As permitted in 240.21. This relinquishes the requirement for an ocpd at the tapping of the busway, but in no way relinquishes the requirement that the tapping conductors must have overcurrent protection. That is dealt with in 240.21. Note also the tapping conductors are categorized as either feeder or branch circuit conductors.

Now let?s look at 409.36 exception 1
Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.
If what has protection? The feeder

You are trying to use the Overcurrent protection for a tap rule to fulfill the requirement for the required feeder protection. The two are different.

No they are not different. The tap conductors ARE the feeder conductors for the panel. Overcurrent protection on a conductor is overcurrent protection regardless of whether it a serves as service, feeder, or branch circuit conductor. Yes, there are some stipulations as to where and how the overcurrent protection must take place in some instances. 408.36 Exception No. 1 has no such stipulations other than the overcurrent protection cannot exceed the rating of the panel. Tap rules achieve overcurrent protection by having an ampacity of not less than the rating of the device supplied (the subpanel) and not less than required to carry the connected load (the panel's branch circuits.

Does the feeder being tapped have Overcurrent protection?

Yes, the 100A main breaker.

The feeder Overcurrent is what would protect the tap in the event of a ground fault or short circuit...

"Feeder" as you have used here I take to be the busway. Also, I take "tap" to mean the tapped conductors. "The tap" is actually the electrical connection, not the conductors.

Your assessment is incorrect. The busway feeder ocpd protects the busway, and the only the busway. It does not protect the tap conductors.

...and the Overcurrent device that the tap is terminated with protects it from Overcurrent.

If there is an overcurrent device at the termination of the tap conductors. Otherwise, the ampacity of the tap conductors must be "not less than the rating of the device supplied".

Protection as outlined in 240.21 is to protect a tap not the feeder that supplies the tap.

"Tap" meaning tap conductors. I have a feeling you are having a hard time accepting that tap conductors can also be feeders.

Let's clarify this:

1) The busways of the main panel are feeder conductors. They are the tapped feeder.
2) The #6 wires are the subpanel feeder conductors. They are the tapping feeder.
3) Nos. 1 and 2 constitute TWO distinct feeders, each having to meet requirements of overcurrent protection... but with regards only to their particular aspect of power distribution, not as though they are the same feeder. Again we're back to if the tap conductors are required to have an ampacity of 100A, they would not be tap conductors.​

There's little point in continuing this discussion unless you agree. I can lead the blind but I can't make 'em see.

I have some errands to take care of now... I'll be back later to see where we stand

 

[Smart $]

How is that an error? What is the "protection" at the load end of the conductors? The lugs are not protecting anything.

The rating of the panel and the calculated load.

Looking at Brett's diagram (and reading the following posts) it seems you're saying that all the branch circuit OCPD's can serve as the protection for the tap. I don't see anything codewise to support that claim.

Not the bccb's but the load they serve, as specified in 240.21(B)(1)(a).

 

[don_resqcapt19]

Smart,

The comprehension of this provision actually starts at 368.17(C), which addresses requirements of feeder and branch circuit tapping of a busway—the busbars in the discussion's main panel.

Article 368 has nothing to do with the question in this thread. The scope of that article only covers busways, and there are no busways involved in this installation.

Not the bccb's but the load they serve, as specified in 240.21(B)(1)(a).

If the calculated load is less than the ampacity of the conductors and the ampacity of the conductors are equal to or greater than the rating of the sub-panel you are correct. Note that all of the provisions of this section must be complied with and it appears that this could be the case
There is one remaining problem...the required protection of the sub-panel. This panel must be protected on its line side at or below the rating of the panel. 408.36(A) We don't have that protection in this case, and if we did it would mean that the rating of the sub-panel is equal to or greater than 100 amps. If that would be the case, then the tap rule in 240.21(B)(1) (b) would be violated. The rules in 240.21 apply to the required overcurrent protection of the conductors , but they do not provide the protection for the sub-panel.
Don

 

[jwelectric]

There's little point in continuing this discussion unless you agree.

Well I don?t guess there is much need to say much more. I would like to ask why you see a need to compare Busways to Panels?
Surely you are not trying to use the rules for Busways for panels are you?

I can lead the blind but I can't make 'em see.

Well I sure do appreciate you running around helping me find my way but I think that I will jerk free for a while and let someone help me with this one, mightily feared that you might be headed the wrong way.

I have some errands to take care of now... I'll be back later to see where we stand

I stand my ground. I just can?t agree with what you are saying because of how it reads.
First you refer to a section of the code that allows 240.21 in an exception. No such exception exists in 408 and 408.36(A) is clear about the feeders in the first exception.

The comprehension of this provision actually starts at 368.17(C), which addresses requirements of feeder and branch circuit tapping of a busway?

Second you claim that a tap is a feeder although 240.2 gives a definition of a tap conductor and it does not call it a feeder. Now When I look at 240.21(B)(1) I see that these conductors are called ?tap conductors? not feeders.

"Feeder" as you have used here I take to be the busway. Also, I take "tap" to mean the tapped conductors. "The tap" is actually the electrical connection, not the conductors.

Now if you want to lead me around some more then don?t take me back to the railroad tracks again. I get a little nervous down there being led around. I can?t tell if it is dark or not and I don?t know whether or not you can see.

 

[LarryFine]

In that drill bit discussion, Larry Fine postes a nice graphical representation of some points he wanted to make about the challagne of drilling in to old work situations.

Larry - did you do that in something like Power Point? And then what is that process to get it to post?

Thanx. Believe it or not, I made those drawings in MS Word, saved them as jpg's, and uploaded them to my site. From there, it's easy to link to them. In this case, I merely posted the images as inserts, using

BBS code.