Can I jumper the line side feed between multiple motor feeder protective devices?

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AC/DC-FAN

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I'm designing a UL-508A 480VAC motor control panel. Are there any limitations per UL 508A or NEC bringing a #8 AWG 480VAC feeder from load side of my main fused disconnect protecting the panel directly down to the line side of my first branch circuit motor feeder breaker and then jumpering #12 AWG 480VAC from that first breaker to multiple other branch circuit motor feeder breakers? The #8 AWG Feeder from the load side of my panel main is sized properly per NEC accounting for 125% of largest OPD + sum of all other motor FLA's. The #12 AWG Feeders jumpering to the other OPD's protecting the smaller motor circuits are sized for the sum of those motor FLA's as well. I know I've seen this type of jumpering done many times in the past but want to be sure I'm doing it correct per code. I'd like to not use a Power Distibution Block.
 
AC/DC-FAN said:
Are there any limitations per UL 508A or NEC bringing a #8 AWG 480VAC feeder from load side of my main fused disconnect protecting the panel directly down to the line side of my first branch circuit motor feeder breaker and then jumpering #12 AWG 480VAC from that first breaker to multiple other branch circuit motor feeder breakers?
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Welcome to the forum.

The first thing that comes to mind is placing multiple wires in lugs not rated for doing that.

AC/DC-FAN said:
I'd like to not use a Power Distibution Block.
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You might be able to use wire-nuts or split-bolts, but it's hard to make them look decent.
 
I made a quick sketch. Seem like the only way to attached or insert to this post is via URL. Does that sound correct?
 
AC/DC-FAN said:
I'm designing a UL-508A 480VAC motor control panel. Are there any limitations per UL 508A or NEC bringing a #8 AWG 480VAC feeder from load side of my main fused disconnect protecting the panel directly down to the line side of my first branch circuit motor feeder breaker and then jumpering #12 AWG 480VAC from that first breaker to multiple other branch circuit motor feeder breakers? The #8 AWG Feeder from the load side of my panel main is sized properly per NEC accounting for 125% of largest OPD + sum of all other motor FLA's. The #12 AWG Feeders jumpering to the other OPD's protecting the smaller motor circuits are sized for the sum of those motor FLA's as well. I know I've seen this type of jumpering done many times in the past but want to be sure I'm doing it correct per code. I'd like to not use a Power Distibution Block.
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petersonra said:
I think it is an improper feeder tap conductor if I understand what you are asking. A sketch would help.
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Hi, I made a sketch but can't figure out how to attach w/o making it URL. I was thinking it may be a feeder tap rule but could not find exact verbiage in NEC to say I couldn't do this. The OCPD for each motor branch is less than 25 ft from all taps.
 
LarryFine said:
Welcome to the forum.

The first thing that comes to mind is placing multiple wires in lugs not rated for doing that.


You might be able to use wire-nuts or split-bolts, but it's hard to make them look decent.
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Yes, I agree, Lugs need to be rated to accept the two wires and AWG. I'll have to look into the split-bolts, have never used them.
 
You need to follow UL508A rules which are not always the same as those found in the NEC.
What do you have against power distribution blocks?
Does your "first' breaker have power distribution lugs as an option?
 
jim dungar said:
You need to follow UL508A rules which are not always the same as those found in the NEC.
What do you have against power distribution blocks?
Does your "first' breaker have power distribution lugs as an option?
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Jim, agreed. I don't see any clear direction on this in UL 508A. I have nothing against PDB's. I do have limited room in this box (retrofit), and also seems a shame to put in a PDB if it's not required by code. Definitely, there are many applications where a PDB is the only way to go, but this application is so simple.
 
AC/DC-FAN said:
Jim, agreed. I don't see any clear direction on this in UL 508A. I have nothing against PDB's. I do have limited room in this box (retrofit), and also seems a shame to put in a PDB if it's not required by code. Definitely, there are many applications where a PDB is the only way to go, but this application is so simple.
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Pdb often have sccr issues.
 
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