Industrial Machinery Article 670 ?

[Davebones]

Have a new piece of equipment coming in . They give me a drawing that shows the FLA as 89 amps at 480 volt . Does the supply conductors have to be rated at 125 % of the FLA ( 670.4 ) ? This would be a continuous duty machine .

 

[petersonra]

It is either a feeder or a branch circuit. The normal rules would apply depending on which it is. Most of the time it's going to be a feeder because it is motor loads and non-motor loads.

 

[Davebones]

Its being fed from a bus duct switch . Would this not mean its a branch circuit ? Would you use 670.3 (A) name plate amperage ? How would you decide if the circuit to it needed to be rated 125% of the FLA on the nameplate ?

 

[Jim1959]

is there a single overcurrent device on the machine?
If so, what size is it?

 

[Davebones]

Finally got some more information from the machine builder . There is a 150 amp disconnect fused at 110 amps on the machine . Going to run a 110 amp circuit to it .

 

[petersonra]

One thing you might want to consider.

If the machine is located an inconvenient distance from the power source, it might make sense to install a MLO panelboard near the machine and power the machine up off a breaker in the panelboard. That way you can use that to disconnect the machine control panel if you need to work inside the control panel. It also gives you a place to add a few circuits down the road if needed. Maybe a 225A panel would make sense.

Even if you decide not to install some kind of local disconnect, it might make sense to run a larger feeder so down the road you can tap off the feeder. Probably is not all the much difference in cost between running (3) #2 and (3) 1/0.

Incidentally 670.4 does not say to use 125% of the FLA as the minimum ampacity of the feeder. Read it carefully. 125% will work and be code compliant but it is not what is actually required.