Hey everyone! I'm designing a control cabinet for a conveyor system that contains some motor protector breakers powering VFDs in the field, 480vac-24vdc power supplies, 480vac-120vac transformer, etc. I'm still new at this in general but also this is the highest amperage panel my company has done so my coworkers do not really know either; we typically deal with <150A feeds but this one is 400A. We build to UL 508A standards and I'm looking for information about what NEC and UL say about it as I'm not sure we are applying to codes correctly. I've attached a little line drawing of an simplified setup but I've also explained the setup and thrown my questions below. It may not matter but the distance from the switch, thru the block, breakers, etc. to the loads or field terminals is less than 10 feet total.
On the side of our enclosure we mount a smaller box that has a fused disconnect switch in it and we'll run wires from the load side of the switch, thru a chase nipple/bushing, into the main enclosure, and then into the line terminals of a power distribution block. Due to the 400A nature, I'm actually wanting to split the load between (2) PDBs (doing 200A each) and to run (2) 000 wires from the switch, one to each PDB; 000 is just easier for our shop to deal with. My first question would be, is it even allowed to run 000 off of a 400 switch like this? I was using the 10' feeder tap rule to say that 000 could do over 10% of the upstream protection. But reading more perhaps this rule only applies when the wire terminates in a OCPD and not to a PDB. Again, we normally just do <150A panels and this feed would be a 0 size in that case which as far as I know there's no issues with.
Leaving the PDB, I've got smaller wires that go off to my various circuits. Some go to various individual breakers, others go to terminal blocks that then have several breakers going to those, and some feeder devices that jumper several breakers together (such as a 140M-C-WBE from AB). Most of these are 14 wire with a breaker directly on the other end. In our normal <150A panels, I assume the 10' rule applies as 14 can do 10% of 150A and it's protected on the other end for <15A. Do these wires now need to be sized to handle 20A (or maybe even 40A)? As I've said, I've also got some wires coming off the PDB that do not directly terminate in an OCPD but rather to terminal blocks or jumper terminal (which then eventually go to multiple breakers). Do these wires need to be sized for the 200A of the PDB (or maybe even the 400A)?
Is there anything that would make terminating to a terminal block, PDB, or the jumper feeder have different rules than say terminating to a terminal on a device?
I apologize if I'm breaking some major rules with this design. As I said, I'm new to panel designs and this size feed is new to my company. I'm looking to learn though and help or code references you all could provide would be great!
On the side of our enclosure we mount a smaller box that has a fused disconnect switch in it and we'll run wires from the load side of the switch, thru a chase nipple/bushing, into the main enclosure, and then into the line terminals of a power distribution block. Due to the 400A nature, I'm actually wanting to split the load between (2) PDBs (doing 200A each) and to run (2) 000 wires from the switch, one to each PDB; 000 is just easier for our shop to deal with. My first question would be, is it even allowed to run 000 off of a 400 switch like this? I was using the 10' feeder tap rule to say that 000 could do over 10% of the upstream protection. But reading more perhaps this rule only applies when the wire terminates in a OCPD and not to a PDB. Again, we normally just do <150A panels and this feed would be a 0 size in that case which as far as I know there's no issues with.
Leaving the PDB, I've got smaller wires that go off to my various circuits. Some go to various individual breakers, others go to terminal blocks that then have several breakers going to those, and some feeder devices that jumper several breakers together (such as a 140M-C-WBE from AB). Most of these are 14 wire with a breaker directly on the other end. In our normal <150A panels, I assume the 10' rule applies as 14 can do 10% of 150A and it's protected on the other end for <15A. Do these wires now need to be sized to handle 20A (or maybe even 40A)? As I've said, I've also got some wires coming off the PDB that do not directly terminate in an OCPD but rather to terminal blocks or jumper terminal (which then eventually go to multiple breakers). Do these wires need to be sized for the 200A of the PDB (or maybe even the 400A)?
Is there anything that would make terminating to a terminal block, PDB, or the jumper feeder have different rules than say terminating to a terminal on a device?
I apologize if I'm breaking some major rules with this design. As I said, I'm new to panel designs and this size feed is new to my company. I'm looking to learn though and help or code references you all could provide would be great!
