JovialBulge
Member
- Location
- New England
- Occupation
- Automation Dude
To start here’s my math using 32.3.1.a)
45+0.42+0.85=46.27
So the MCCB should not be higher than this value. However, section b) of 32.3.1 states "The ampacity of the conductors or bus bars on the load side of the overcurrent device."
Now the MCCB would usually have a distribution lug attached to it on the load side, from there we would then do our wire runs to the line side of the 3 BCPD devices (in our case it will be class cc fuse folders) then from there out to the final devices that they protect.
The VFD will have a 45 A fuse protecting it, so I will have a 6 AWG wire from the MCCB distribution lug to the fuses. The other two fuse holders will have 14 AWG wires, since that's the smallest I can use there regardless of the amperage.
Can the MCCB be 50 A instead of 45 A that I calculated above based on using section b) from 32.3.1? Or am I misunderstanding something there? The 6 AWG wire, which will be the largest on the load side of the MCCB, can handle 55 A, clearly the 14 AWG cannot.
45+0.42+0.85=46.27
So the MCCB should not be higher than this value. However, section b) of 32.3.1 states "The ampacity of the conductors or bus bars on the load side of the overcurrent device."
Now the MCCB would usually have a distribution lug attached to it on the load side, from there we would then do our wire runs to the line side of the 3 BCPD devices (in our case it will be class cc fuse folders) then from there out to the final devices that they protect.
The VFD will have a 45 A fuse protecting it, so I will have a 6 AWG wire from the MCCB distribution lug to the fuses. The other two fuse holders will have 14 AWG wires, since that's the smallest I can use there regardless of the amperage.
Can the MCCB be 50 A instead of 45 A that I calculated above based on using section b) from 32.3.1? Or am I misunderstanding something there? The 6 AWG wire, which will be the largest on the load side of the MCCB, can handle 55 A, clearly the 14 AWG cannot.