Strahan
Senior Member
- Location
- Watsontown, PA
Scenario: Installing a motor control panel housing the controls for 3 pumps rated at 30hp each.
Each pump will be protected with an inverse time breaker by looking at 430.250 it is determined to use 40amp in calculations so:
pump 1 40 x 250%=100A
pump 2 40 x 250%=100A
pump 3 40 x 250%=100A
So each will be using a 100A inverse time breaker for protection. The 250% came from 430.52.
Next main disconnect located in panel will also be an inverse time breaker so;
100A + 40A + 40 = 180A
This is not a standard size so next size up rule applies giving me a 200A breaker.
Feeder conductor size: 125% of full-load current rating of the highest rated motor plus the sum of the full-load current ratings of all the other motors so:
40A x 1.25 = 50 + 40 + 40 = 130Amps
Using table 310.16 75deg column size 1AWG copper.
Now for my question how or where do I find how to determine the size of breaker supplying the feeder conductors? This run will be approx. 200' from the service and I'm not exactly sure how to size the breaker at the service.
Thanks for your help!!!
Each pump will be protected with an inverse time breaker by looking at 430.250 it is determined to use 40amp in calculations so:
pump 1 40 x 250%=100A
pump 2 40 x 250%=100A
pump 3 40 x 250%=100A
So each will be using a 100A inverse time breaker for protection. The 250% came from 430.52.
Next main disconnect located in panel will also be an inverse time breaker so;
100A + 40A + 40 = 180A
This is not a standard size so next size up rule applies giving me a 200A breaker.
Feeder conductor size: 125% of full-load current rating of the highest rated motor plus the sum of the full-load current ratings of all the other motors so:
40A x 1.25 = 50 + 40 + 40 = 130Amps
Using table 310.16 75deg column size 1AWG copper.
Now for my question how or where do I find how to determine the size of breaker supplying the feeder conductors? This run will be approx. 200' from the service and I'm not exactly sure how to size the breaker at the service.
Thanks for your help!!!