UL508A Power Distribution Block

D

doomed9

Member
Location
Hopkinton, MA
Occupation
Control Systems Designer
I am designing a UL508a panel that has a MCCB of 125A acting as my disconnect switch. Downstream of that disconnect I am looking to install a UL listed power distribution block to connect to my branch circuits. The PDB accepts 1 AWG wire Line side, however load side it only accepts a 4-14 AWG. I want to connect 8 AWG wire to it as I need 50A for my branch circuits. Am I allowed to connect lower ampacity wires to the load side of a PDB if I used circuit protection soon after the PDB? Thank you for any help.
 
It has nothing to do with overcurrent protection. The load side termination is simply not designed for use with conductors smaller than 4 AWG.
 
Be careful with PDBs with regard to SCCR and series listings. Most are only listed at 5-10kA unless protected by FUSES. In some cases you might find distribution LUGS for the CB itself that will be listed with the CB at its rated kAIC, that’s often a better route if you want to avoid fuses.
 
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