Current in Paralleled Conductors
- Thread starter bphgravity
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john m. caloggero
Senior Member
Re: Current in Paralleled Conductors
There is no problem with the arrangement as described, until the load is increased to the ampere rating of the smallest conductor. In this instance, the ampacity of No. 1, Cu is 150A for 90 degree C insulation, but limited to 130A because of the 75 degree terminations. The 1/0 has an ampacity of 170A but limited to 150A. Using the DC resistance values provided in Table 8, chapter 9.
0.0122/(.0122+.0154)x(2x130)= 114.9A
0.0154/(.0122+.0154)x(2x130)= 145.0A
The terminations are rated at 75degrees C so they are operating close to their maximum rating for one of the conductors.
If the load was based on the larger conductor times 2, the result would be 132.6A and 167.4A which would be greater than the load permitted for 75 degree terminations.
There is no problem with the arrangement as described, until the load is increased to the ampere rating of the smallest conductor. In this instance, the ampacity of No. 1, Cu is 150A for 90 degree C insulation, but limited to 130A because of the 75 degree terminations. The 1/0 has an ampacity of 170A but limited to 150A. Using the DC resistance values provided in Table 8, chapter 9.
0.0122/(.0122+.0154)x(2x130)= 114.9A
0.0154/(.0122+.0154)x(2x130)= 145.0A
The terminations are rated at 75degrees C so they are operating close to their maximum rating for one of the conductors.
If the load was based on the larger conductor times 2, the result would be 132.6A and 167.4A which would be greater than the load permitted for 75 degree terminations.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Current in Paralleled Conductors
Please allow me to clarify: I infer that you mean there is no physics problem. We all know that it still violates 310.4. Once in a while, as we get off into discussing these strange situations, we need to remind ourselves that academic discussions, design considerations, and code issues are distinct subjects.
james wuebker
Senior Member
- Location
- Iowa
Re: Current in Paralleled Conductors
Charlie, you wrote:
quote:
--------------------------------------------------------------------------------
Originally posted by john m. caloggero: There is no problem with the arrangement as described, until the load is increased to the ampere rating of the smallest conductor.
--------------------------------------------------------------------------------
Please allow me to clarify: I infer that you mean there is no physics problem. We all know that it still violates 310.4. Once in a while, as we get off into discussing these strange situations, we need to remind ourselves that academic discussions, design considerations, and code issues are distinct subjects.
Charlie, question: It looks like the #1 was feed to a piece of equipment and the 1/0 wire was feed to another piece of equipment off this 225 amp breaker. Let's say that at the 225 amp breaker, they had the correct type of lugs installed for the #1 & 1/0 wire. Now where each wire ended up at they had and breaker or disconnect with it being fused for that wire size or load. Would this now be a violation? I know we see this type of hook up a lot if you think about it. Say we have a 200 amp disconnect off the meter. From there we might sub off to 2 different panels. Is this the same process like above topic? Just thinking about it.
Thanks!
Jim
Charlie, you wrote:
quote:
--------------------------------------------------------------------------------
Originally posted by john m. caloggero: There is no problem with the arrangement as described, until the load is increased to the ampere rating of the smallest conductor.
--------------------------------------------------------------------------------
Please allow me to clarify: I infer that you mean there is no physics problem. We all know that it still violates 310.4. Once in a while, as we get off into discussing these strange situations, we need to remind ourselves that academic discussions, design considerations, and code issues are distinct subjects.
Charlie, question: It looks like the #1 was feed to a piece of equipment and the 1/0 wire was feed to another piece of equipment off this 225 amp breaker. Let's say that at the 225 amp breaker, they had the correct type of lugs installed for the #1 & 1/0 wire. Now where each wire ended up at they had and breaker or disconnect with it being fused for that wire size or load. Would this now be a violation? I know we see this type of hook up a lot if you think about it. Say we have a 200 amp disconnect off the meter. From there we might sub off to 2 different panels. Is this the same process like above topic? Just thinking about it.
Thanks!
Jim
pierre
Senior Member
- Location
- Westchester County, New York
Re: Current in Paralleled Conductors
If the 2 sets of conductors are in the same conduit, but terminate in two different pieces of equipment, that is fine as this would not be a parallel installation.
"parallel(electrically joined at both ends)."
[from the '05 NEC, the last sentence in 310.4.
the other considerations would be 300.3(B), 310.15(B)(2)(a), and pipe fill, as per Chapter 9.
If the 2 sets of conductors are in the same conduit, but terminate in two different pieces of equipment, that is fine as this would not be a parallel installation.
"parallel(electrically joined at both ends)."
[from the '05 NEC, the last sentence in 310.4.
the other considerations would be 300.3(B), 310.15(B)(2)(a), and pipe fill, as per Chapter 9.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Current in Paralleled Conductors
I had asked that question, and was told it was a parallel connection. Please follow the link in the first post of this thread, and look for the post in that other thread by ?spider2? on May 16, at 9:11 pm.
james wuebker
Senior Member
- Location
- Iowa
Re: Current in Paralleled Conductors
Sorry Charlie,
I miss read that and your are correct.
Thanks!
Jim
Sorry Charlie,
I miss read that and your are correct.
Thanks!
Jim
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