DLO Ampacity for Close-Coupled Gear

[david luchini]

He said there are (6) sets of 444 kcmil RHH/RHW-2/DLO conductors that run from the XFMR secondary terminals, through a window cut out between the XFMR & SWBD, and to the SWBD main breaker. It is not a long jump to the conclusion that there are no special terminations on the transformer side or the SWBD side to avoid the use of Section 110.14(C)(1) which forces the reader to Table 310.15(B)(16).

Who said anything about avoiding the use of 110.14(C)(1)?

The problem is 110.14(C)(1) doesn't say what you think it says.

 

[ron]

Who said anything about avoiding the use of 110.14(C)(1)?

The problem is 110.14(C)(1) doesn't say what you think it says.

110.14(C)(1) seems to say to me that unless the equipment is listed and marked otherwise, the conductor ampacity associated with the terminations get determined based on Table 310.15(B)(16) or as modified for for single phase dwellings.

 

[david luchini]

110.14(C)(1) seems to say to me that unless the equipment is listed and marked otherwise, the conductor ampacity associated with the terminations get determined based on Table 310.15(B)(16) or as modified for for single phase dwellings.

That's not what it says. It says the conductor ampacity used in determining equipment termination provisions shall be base on T310.15(B)(7)...

310.15(B) says Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).


110.14(C)(1) tells you that if you have an equipment termination that is rated for (2) #1/0-#3/0 conductors, the termination is rated for 400Amps.

310.15(B)(16) as modified by 310.15(B)(2)(A) tells you that you can use two sets of #2/0 conductors (in separate raceways) in a 65degF ambient to carry a 380A load connected to the termination that is rated for 400A.

 

[ron]

I

That's not what it says. It says the conductor ampacity used in determining equipment termination provisions shall be base on T310.15(B)(7)...

310.15(B) says Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).


110.14(C)(1) tells you that if you have an equipment termination that is rated for (2) #1/0-#3/0 conductors, the termination is rated for 400Amps.

310.15(B)(16) as modified by 310.15(B)(2)(A) tells you that you can use two sets of #2/0 conductors (in separate raceways) in a 65degF ambient to carry a 380A load connected to the termination that is rated for 400A.

I will take a look. Thanks for spelling it out.

 

[oldsparky52]

That's not what it says. It says the conductor ampacity used in determining equipment termination provisions shall be base on T310.15(B)(7)...

310.15(B) says Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).


110.14(C)(1) tells you that if you have an equipment termination that is rated for (2) #1/0-#3/0 conductors, the termination is rated for 400Amps.

310.15(B)(16) as modified by 310.15(B)(2)(A) tells you that you can use two sets of #2/0 conductors (in separate raceways) in a 65degF ambient to carry a 380A load connected to the termination that is rated for 400A.

I've never seen it put this way.

David, assume type W cable in a single-phase system where the neutral is carrying the unbalanced load (120/240, not 120/208), table 400.5(A)(2) gives the ampacity of a 1/0 cable as 207 amps. May I use that cable to feed a power center at a marina at 200-amps and connect it to a 200-amp breaker in the panel?

Because of 110.14(C), the local AHJ says no. The wording you used above makes me wonder if yes, it would be okay (I will admit I'm a little confused as to exactly the point you are making).

 

[oldsparky52]

110.14(C)(1) tells you that if you have an equipment termination that is rated for (2) #1/0-#3/0 conductors, the termination is rated for 400Amps.

If it is a Cu/Al rated termination, does that change things since (2) #3/0 Al conductors at 75C are not rated 400-amps?

 

[ron]

That's not what it says. It says the conductor ampacity used in determining equipment termination provisions shall be base on T310.15(B)(7)...

310.15(B) says Ampacities for conductors rated 0 to 2000 volts shall be as specified in the Allowable Ampacity Table 310.15(B)(16) through Table 310.15(B)(19), and Ampacity Table 310.15(B)(20) and Table 310.15(B)(21) as modified by 310.15(B)(1) through (B)(7).


110.14(C)(1) tells you that if you have an equipment termination that is rated for (2) #1/0-#3/0 conductors, the termination is rated for 400Amps.

310.15(B)(16) as modified by 310.15(B)(2)(A) tells you that you can use two sets of #2/0 conductors (in separate raceways) in a 65degF ambient to carry a 380A load connected to the termination that is rated for 400A.

David,

I put some thought into your explanation. In this case with 4000A SWBD, I will guess there is copper bus detail for field applied wire connectors to be bolted.

Considering that 110.14(C)(1) is used in determining equipment termination provisions, and although I can't find a definition for equipment termination provisions, it seems to include the factory terminal (copper bus detail) and the field applied wire connector (compression connector of some type because they are using fine stranded wire), the link below shows that it is single sized per conductor.
http://www.tnb.com/pubint/docs/colorkeyed_spec.pdf

Since the 444kcmil fine stranded wire only has dedicated connectors, and we are directed by 110.14(C)(1) to use 310.15(B)(16) for determining equipment termination provisions, it would seem that we are back to where we started. Sizing it based on 400kcmil in the 75 deg column where 6 sets are 2010A.

The only way he can use the "other" ampacity tables, is if he used some type of transition box pair in between which is not practical in this application, AND where the bus detail in the transition box on both ends were "equipment is listed and marked otherwise".

 

[david luchini]

Since the 444kcmil fine stranded wire only has dedicated connectors, and we are directed by 110.14(C)(1) to use 310.15(B)(16) for determining equipment termination provisions, it would seem that we are back to where we started. Sizing it based on 400kcmil in the 75 deg column where 6 sets are 2010A.

But you wouldn't have a 400mcm connector (you wouldn't even have a 400mcm conductor.) With the information given, we only know the size and type of conductor, not the size (or temperature rating) of the termination.
You are trying to force a rating onto the termination based on the conductors supplied rather than the actual rating of the termination.

 

[david luchini]

I've never seen it put this way.

David, assume type W cable in a single-phase system where the neutral is carrying the unbalanced load (120/240, not 120/208), table 400.5(A)(2) gives the ampacity of a 1/0 cable as 207 amps. May I use that cable to feed a power center at a marina at 200-amps and connect it to a 200-amp breaker in the panel?

Because of 110.14(C), the local AHJ says no. The wording you used above makes me wonder if yes, it would be okay (I will admit I'm a little confused as to exactly the point you are making).

240.5 says that flexible cords and cables shall be protected by an overcurrent device in accordance with their ampacity as specified in Table 400.4(A)(1) and Table 400.5(A)(2), so yes, you could protect the 1/0 cable with a 200A breaker.

The point I am trying to make is that the termination must be rated for 200A also. You couldn't use a termination or connector that was listed for a max. 1/0 conductor, as that termination would only be rated for 150A.

 

[oldsparky52]

240.5 says that flexible cords and cables shall be protected by an overcurrent device in accordance with their ampacity as specified in Table 400.4(A)(1) and Table 400.5(A)(2), so yes, you could protect the 1/0 cable with a 200A breaker.

The point I am trying to make is that the termination must be rated for 200A also. You couldn't use a termination or connector that was listed for a max. 1/0 conductor, as that termination would only be rated for 150A.

Do you put any credibility into the NEC handbooks?

 

[david luchini]

Do you put any credibility into the NEC handbooks?

Some, not completely. Which section would you like me to read?

 

[oldsparky52]

The most current issue I own is the 2011 edition. There is a calculation example that starts in 400.5, page 509 of my book. The paragraph I would like you to read/comment on is step 3 (which on page 511 of my book).

 

[oldsparky52]

Here is a pic of that paragraph

 

[david luchini]

The most current issue I own is the 2011 edition. There is a calculation example that starts in 400.5, page 509 of my book. The paragraph I would like you to read/comment on is step 3 (which on page 511 of my book).

That commentary is similar to what I've been saying, but their example already forced you to a 3/0 conductor based on temperature and CCC adjustments. (The example is wrong in that they start the derating from 200A even though they tell you that the 200A includes the 25% increase for continuous load...the derating should start from the actual feeder load without the added 25% for continuous load.)

What I'm saying is that your 1/0 with an ampacity of 207 would have to be connected to a termination that is rated for 3/0 conductors (200A).

 

[oldsparky52]

That commentary is similar to what I've been saying, but their example already forced you to a 3/0 conductor based on temperature and CCC adjustments. (The example is wrong in that they start the derating from 200A even though they tell you that the 200A includes the 25% increase for continuous load...the derating should start from the actual feeder load without the added 25% for continuous load.)

What I'm saying is that your 1/0 with an ampacity of 207 would have to be connected to a termination that is rated for 3/0 conductors (200A).

I guess I'm not understanding you because that example to me specifically points to using table 310.15(B)(16) to comply with 110.14(C), and because this cable is being used at 200-amps it does. If it was used at a higher ampacity (it's rated to 241-amps) it would not comply.

 

[Sunny_92]

The conductors are terminated on both ends with Thomas & Betts lugs that are properly rated for the stranding.

Very interesting discussion so far... I definitely see the point David is trying to make about what 110.14(C)(1) says. I guess my biggest hangup with using table 310.15(B)(17) is that I'm not sure that conductors that are inside gear really meet the definition of "free air".

 

[ron]

The conductors are terminated on both ends with Thomas & Betts lugs that are properly rated for the stranding.

I guess my biggest hangup with using table 310.15(B)(17) is that I'm not sure that conductors that are inside gear really meet the definition of "free air".

I agree with you.

I also think that the T&B lugs are probably only rated for 444kcmil conductors, and the terminations (factory terminals with the T&B connectors) would only be good for 2010A.