# Fixing a 240.21(B)(2) issue. Oops...



## Chris Kennedy (Nov 19, 2007)

Today I rebuilt a 1000A 208 system due to undersized conductors. I designed this, had it stamped by EE, approved by plans reviewer and permit issued. Around 6hrs into this I see what I believe is a serious flaw in the design. I'll try to explain the riser diagram.

Poco comes underground into 1200A main fused at 1000 with 3 sets of 400cu.

3 sets of 350cu leave load side of main into wireway above.

Taps from the wireway consist of the following;

1) 4 500cu into 600A meter with two sets of 4 3/0 feeding 2 200A discos

2) 1 set of 3/0cu into 200A meter feeding 200A disco

3) 4 500cu into 600A meter with two sets of 4 3/0 feeding 2 200A discos

All the above conductors are under 10', no 250 issues, no 220 issues. The issue can be found in the info given.


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## BBQ (Nov 16, 2010)

3 sets of 350 cu sounds light for 1200 amps.


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## backstay (Feb 3, 2011)

I get 930 amps max for 3-350 in parallel with no adjustments.


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## Chris Kennedy (Nov 19, 2007)

BBQ said:


> 3 sets of 350 cu sounds light for 1200 amps.


Crap, I was going to say you missed the fact that its fused at 1000, but checked 310.15 and see I'm also in violation of 240.4(B).

There is another problem I was thinking of here Bob, and you should know what it is. You pointed it out to me a while back on another one of my installs.


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## Dennis Alwon (May 9, 2009)

Where's the meter for set #2?


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## Cletis (Aug 20, 2010)

*?*

The tap conductors are installed in a raceway if they leave the enclosure???

The ampacity of the tap conductor is not less than the computed load in accordance with Art. 220, and not less than the rating of the device supplied by the tap conductors or the OCPD at the termination of the tap conductors.???


Probably wrong...just throwing things out there

Cletis


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## Chris Kennedy (Nov 19, 2007)

Dennis Alwon said:


> Where's the meter for set #2?


All meters are immediately adjacent to the main. What are you getting at? I see, fixed it.



Cletis said:


> The tap conductors are installed in a raceway if they leave the enclosure???
> 
> The ampacity of the tap conductor is not less than the computed load in accordance with Art. 220, and not less than the rating of the device supplied by the tap conductors or the OCPD at the termination of the tap conductors.???


No, thats all good.


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## Dennis Alwon (May 9, 2009)

Can a tap conductor go thru two enclosures??? 

I was getting at the fact that you didn't mention a meter is #2.


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## Chris Kennedy (Nov 19, 2007)

Dennis Alwon said:


> Can a tap conductor go thru two enclosures???


Thats close.



> I was getting at the fact that you didn't mention a meter is #2.


Sorry, fixed that.


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## kaboler (Dec 1, 2010)

Chris Kennedy said:


> 2) 1 set of 3/0cu into 200A meter feeding 200A disco


Will you melt your meter if you hit 200A?

Also, the power company might like the disconnects before the meter, not after, because now they have to shut the whole building down to kill services to 1 unit. It's not like residential where they can disconnect people from the transformer. Maybe I got this backwards.


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## Chris Kennedy (Nov 19, 2007)

kaboler said:


> Maybe I got this backwards.


There is a 1200A SS fused at 1000A before any meters.


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## kaboler (Dec 1, 2010)

But if you want to cut 1 customer's power and not the other 2, how would you do it?

Okay that's not the answer. I'm going to draw it out.


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## kaboler (Dec 1, 2010)

Can't the power company supply a neutral? Or are we talking about only conductors?


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## HARRY304E (Sep 15, 2010)

kaboler said:


> Can't the power company supply a neutral? Or are we talking about only conductors?


 Only if they want to..:laughing:


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## walkerj (May 13, 2007)

kaboler said:


> Can't the power company supply a neutral? Or are we talking about only conductors?


You are a GREAT electrician. 




Chris,
First off, go tigers!
Second, it sounds good to me. 
Third, does it have something to do with the sizes of the tapped disconnects?

Sent from my iPhone using ET Forum


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## kaboler (Dec 1, 2010)

HARRY304E said:


> Only if they want to..:laughing:


I did a side job insulating and I noticed that residential guys get 2 hots and a copper jacket around the 2 conductors. I think that's the neutral. I dunno.

Anyway, trying to draw it out. Getting confused between sets and numbers of wires lol. Dang, but I'm anxious. I like these pluzzles you guys put up.


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## Dennis Alwon (May 9, 2009)

> (2) The tap conductors do not extend beyond the switchboard, panelboard, disconnecting means, or control devices they supply.
> (3) Except at the point of connection to the feeder, the tap conductors are enclosed in a raceway, which shall extend from the tap to the enclosure of an enclosed switchboard, panelboard, or control devices, or to the back of an open switchboard.


Sounds like these taps do not comply with #3


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## kaboler (Dec 1, 2010)

walkerj said:


> You are a GREAT electrician.
> 
> Second, it sounds good to me.
> Third, does it have something to do with the sizes of the tapped disconnects?


"The issue can be found in the info given" 

I will be a great electrician because I'm taking something real, and trying to find out if it's code. You? Guessing. Hahahahaha.


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## kaboler (Dec 1, 2010)

Dennis Alwon said:


> Sounds like these taps do not comply with #3


That's what I said too. Disconnect then meter. Hope you're right.

Too bad I would be right for the wrong reason.


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## ColoradoMaster3768 (Jan 16, 2010)

Chris Kennedy said:


> Today I rebuilt a 1000A 208 system due to undersized conductors. I designed this, had it stamped by EE, approved by plans reviewer and permit issued. Around 6hrs into this I see what I believe is a serious flaw in the design. I'll try to explain the riser diagram.
> 
> Poco comes underground into 1200A main fused at 1000 with 3 sets of 400cu.
> 
> ...


 
I'll take a stab at # 2) above: "1 set of 3/0cu into 200A meter feeding 200A disco"


And, refer to 240.21 (B) (2) (1): The ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors.


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## Dennis Alwon (May 9, 2009)

ColoradoMaster3768 said:


> I'll take a stab at # 2) above: "1 set of 3/0cu into 200A meter feeding 200A disco"
> 
> And, refer to 240.21 (B) (2) (1): The ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors.


He said all taps were less then 10' so 240.21(B)(2)(1) would not apply. 240.21(B)(1) applies.


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## ColoradoMaster3768 (Jan 16, 2010)

Dennis Alwon said:


> He said all taps were less then 10' so 240.21(B)(2)(1) would not apply. 240.21(B)(1) applies.


 
Yes, he did, but he also titled the conversation: *"Fixing a 240.21(B)(2) issue..."*


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## Dennis Alwon (May 9, 2009)

ColoradoMaster3768 said:


> Yes, he did, but he also titled the conversation: *"Fixing a 240.21(B)(2) issue..."*


Well darn.... something is amiss. :laughing:


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## electricalperson (Jan 11, 2008)

the way i read 240.21B1 the ampacity of the tap conductors cant be less than the rating of where it terminates too. i believe terminating 500s in a 600 amp meter enclosure is a violation. i might be wrong but were you thinking of the 25 foot tap rule where you had to terminate the taps to OCPD's? another issue is the 3 sets of 350s protected by a 1000 amp breaker thats a violation of 240.4C. i hope im not terribly wrong but that is my opinion on what might be wrong


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## Chris Kennedy (Nov 19, 2007)

The original install done in the 80's was in violation of 240.21(B)(2), all 3/0's leaving the load side of main, all over 10' long. 

Do you see a problem with the the tap for following?

4 500cu into 600A meter with two sets of 4 3/0 feeding 2 200A discos


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## ColoradoMaster3768 (Jan 16, 2010)

Chris Kennedy said:


> The original install done in the 80's was in violation of 240.21(B)(2), all 3/0's leaving the load side of main, all over 10' long.
> 
> Do you see a problem with the the tap for following?
> 
> 4 500cu into 600A meter with two sets of 4 3/0 feeding 2 200A discos


 
Yes, but I believe some confusion was created with the statement: "All the above conductors are under 10', no 250 issues, no 220 issues." This caused most to focus on 240.21 (B) (1). 


Also with my understanding of the statement of conditions originally posted, I still think Section 240.21 (B) (2) (1) is also applicable for the set of 3/0 Cu conductors serving the 200A disconnect: "The ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors."


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## Chris Kennedy (Nov 19, 2007)

ColoradoMaster3768 said:


> Also with my understanding of the statement of conditions originally posted, I still think Section 240.21 (B) (2) (1) is also applicable for the set of 3/0 Cu conductors serving the 200A disconnect: "The ampacity of the tap conductors is not less than one-third of the rating of the overcurrent device protecting the feeder conductors."


All the tap conductors now meet the requirements of 240.21(B)(1). Here is what I see as a violation with the double lugged meter bases.



> 240.21 Location in Circuit.
> Overcurrent protection shall be provided in each ungrounded circuit conductor and shall be located at the point where the conductors receive their supply except as specified in 240.21(A) through (H). Conductors supplied under the provisions of 240.21(A) through (H) shall not supply another conductor except through an overcurrent protective device meeting the requirements of 240.4.


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## ColoradoMaster3768 (Jan 16, 2010)

Chris Kennedy said:


> All the tap conductors now meet the requirements of 240.21(B)(1). Here is what I see as a violation with the double lugged meter bases.


 
OK, got it now Chris; it is _not _*"**a 240.21(B)(2) issue"* after all. Thanks


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## Greg (Aug 1, 2007)

kaboler said:


> Will you melt your meter if you hit 200A?
> 
> Also, the power company might like the disconnects before the meter, not after, because now they have to shut the whole building down to kill services to 1 unit. It's not like residential where they can disconnect people from the transformer. Maybe I got this backwards.


No, Chances are the meter is a 320, even it did it is the POCO's problem not his.

As far as the disco before the meter, he said it was 208vac not 480vac. I also deal with the same POCO's he deals with and we are only required to put a disco before the meter if it is 480vac.


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## electricalperson (Jan 11, 2008)

i still think terminating a 500 mcm tap in a 600amp enclosure is a code violation of 240.21B1

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


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## Chris Kennedy (Nov 19, 2007)

electricalperson said:


> i still think terminating a 500 mcm tap in a 600amp enclosure is a code violation of 240.21B1
> 
> The ampacity of the tap conductors is :
> a. Not less than the combined calculated loads on the circuits supplied by the tap conductors and
> ...


The 600A meter bases are over sized, each feed two 200A discos. Probably an EE's spec for the original install. So the 200A discos are the devices being supplied, not the cash registers.


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## electricalperson (Jan 11, 2008)

Chris Kennedy said:


> The 600A meter bases are over sized, each feed two 200A discos. Probably an EE's spec for the original install. So the 200A discos are the devices being supplied, not the cash registers.


just the way i interpret the code, where the conductors terminate is the device being supplied. i understand that you need a breaker or set of fuses if you have to supply other conductors. i just figured that the device where the conductors terminate is the device supplied and it doesnt matter what the load is attached too 

maybe i am just overthinking the whole situation i personally would of put a 400 amp meter socket instead.


the definition of device according to the NEC is 

Device: A unit of an electrical system that carries or controls electric energy as its principal function.

a meter socket is a device because it carries electrical energy to the load


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## Chris Kennedy (Nov 19, 2007)

The way I'm reading 90.2(B)(5) the meter base does not exist in the eyes of the NEC.



> 90.2(B)(5) Installations under the exclusive control of an electric utility where such installations
> a. Consist of service drops or service laterals, and associated metering


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## electricalperson (Jan 11, 2008)

Chris Kennedy said:


> The way I'm reading 90.2(B)(5) the meter base does not exist in the eyes of the NEC.


but its installed on the load side of the service so is it still a meter base owned by the poco? i know the meter itself is poco property but i think the meter socket on the load side of the service should fall under the NEC


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## Chris Kennedy (Nov 19, 2007)

electricalperson said:


> but its installed on the load side of the service so is it still a meter base owned by the poco? i know the meter itself is poco property but i think the meter socket on the load side of the service should fall under the NEC


Its a good point Chris, in the 80's meter bases were supplied by POCO so your read is as valid as mine.


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## PDX-SPARKY (Mar 5, 2010)

Never mind thought I had something constructive......:whistling2:


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