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Old 06-12-2010, 10:47 PM   #1
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Question 600 amp parallel feed

i have a 600 amp panel with parallel feeds in two different runs of conduit.
one run of conduit has 3 500 kcmil and a 4/0 for ground.
second one has 3 3/0 thhn and a 1 awg for ground.
(IS THIS CODE) can you run different size wire on a parallel feed.

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Old 06-12-2010, 10:50 PM   #2
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Whether it is right or wrong is a consideration that you should have thought about before you pulled the wire...or you just trying to test us?

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Old 06-12-2010, 11:01 PM   #3
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Default 600 amp parallel feed

i'm a contractor who is setting up a new machine, and need to pull out of this panel
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Old 06-12-2010, 11:22 PM   #4
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The parallel conductors need to be the same length, material, size, insulaation, and terminated in the same manner. 310.4
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Old 06-13-2010, 04:41 AM   #5
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Quote:
Originally Posted by industrialboy View Post
i have a 600 amp panel with parallel feeds in two different runs of conduit.
one run of conduit has 3 500 kcmil and a 4/0 for ground.
second one has 3 3/0 thhn and a 1 awg for ground.
(IS THIS CODE) can you run different size wire on a parallel feed.
The answer is no you can not run diffrent size conductor it must be the same size as the other set of conductors and the length is the same and type as well.

Look up in 310.4 plus few other spots IIRC

And you will run some issue with unbalanced conductors current drawage { I am pas joking on this one }

Merci.
Marc
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Old 06-13-2010, 10:45 AM   #6
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Originally Posted by frenchelectrican View Post
The answer is no you can not run diffrent size conductor it must be the same size as the other set of conductors and the length is the same and type as well.

Look up in 310.4 plus few other spots IIRC

And you will run some issue with unbalanced conductors current drawage { I am pas joking on this one }

Merci.
Marc
Oui , Vous etes correct. Just practising my french.
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Old 06-13-2010, 02:06 PM   #7
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Feeder into the breaker or load side of the breaker.
Is this a feeder leaving the breaker and going to two separate loads or is this feeding the line side of the breaker?
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Old 07-10-2010, 10:54 PM   #8
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Quote:
Originally Posted by industrialboy View Post
i have a 600 amp panel with parallel feeds in two different runs of conduit.
one run of conduit has 3 500 kcmil and a 4/0 for ground.
second one has 3 3/0 thhn and a 1 awg for ground.
(IS THIS CODE) can you run different size wire on a parallel feed.
In agreement with the other posters, this is a code violation for parallel feeds. I want to add that this is a very dangerous situation. Remember that current will flow through the path of least resistance which, in this case, is the set of 500s. Most of the load will try to use this path, rendering the 3/0s useless. If the service is loaded to more than 430a, the 500s will overheat without tripping the breaker until there's a dead short inside the conduit. This condition can also result if there's any appreciable difference in the lengths of feeder conductors, even if they're the same size.
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Old 07-10-2010, 11:07 PM   #9
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In agreement with the other posters, this is a code violation for parallel feeds. I want to add that this is a very dangerous situation. Remember that current will flow through the path of least resistance which, in this case, is the set of 500s. Most of the load will try to use this path, rendering the 3/0s useless. If the service is loaded to more than 430a, the 500s will overheat without tripping the breaker until there's a dead short inside the conduit. This condition can also result if there's any appreciable difference in the lengths of feeder conductors, even if they're the same size.

Current is not guaranteed to divide in any specific quantity, resistance of conductors and resistance of connections together determine how much current flows on which conductor, you could easily have the 3/0 carrying the majority of the current if you have a higher resistance connection on the 500.
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Old 07-10-2010, 11:31 PM   #10
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Quote:
Originally Posted by industrialboy View Post
i have a 600 amp panel with parallel feeds in two different runs of conduit.
one run of conduit has 3 500 kcmil and a 4/0 for ground.
second one has 3 3/0 thhn and a 1 awg for ground.
(IS THIS CODE) can you run different size wire on a parallel feed.
Totally wrong. The panel may work fine without much load but as others have said if the load gets up there you will have issues.

You need to have parallel 300kcm copper conductors if the calculated load on the panel is 570 amps or less. Art. 240.4(B) allows us to use the next size breaker -- 600 amps.

Your egc needs to be based on the 600 amp breaker from T. 250.122. This means you need a #1 copper conductor in both raceways.

When you say 4/0 for ground and #1 for ground are you meaning neutral or the EGC (equipment grounding conductor)?

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