Disconnecting Means for Feeders to Several Motor Disconnects

[Mr. Spinosa]

Anyone care to elaborate on 430.110(1)? How and when is this applied? When would you need to use this calculation and how would you properly use it? I have an example of three motors, all rated differently, (FLC's are 169 Amps, 114 Amps, and 30.8 Amps.). If you add them all together and then multiply them by 115% as shown in 430.110(A) you get 360.87... So you use a 400 Amp rated disconnect? Is this the correct way to figure the feeder disconnect size or do you have to somehow use 430.110(C)(1)? To me it looks like you have to do a much more complicated calculation using 430.110(C)(1) since this would fall under the "two or more motors used together" stipulation. - Anyway, some good advice would be appreciated. Thank you.

 

[Joethemechanic]

Heck if I know,

Ask Bob (iwire)

* Moderators Note Post has been edited to remove profanity lets keep it clean

 

[Cow]

If you add them all together and then multiply them by 115% as shown in 430.110(A) you get 360.87... So you use a 400 Amp rated disconnect?

That's how I'd do it. I'd verify it by making sure the disconnect HP rating met or exceeded the combined HP of all the motors too.

 

[kwired]

I think you need to consider both 410.110(C) and 410.110(C)(1).

If one would require a larger switch than the other, the larger switch must be used.