Sizing Circuit Breakers

[gphillips]

During normal operation the maximum current draw on my process is 2Amps.
However, the outputs can be turned on via a service screen that would draw 8Amps if they were all turned on.

Should the breaker be sized for normal operation, and the service screen modified so that only certain outputs can be turned on at any given time? Or should it be sized to accommodate the maximum load possible even though it would never see that during normal operation?

 

[Jimmie_Ohio]

In my personal opinion, I would handle this like sequentially energizing several motor starters to avoid a huge surge "across the line".

Since you have the PLC, use it to your advantage and sequence the outputs offset by a few tenths of a second each.

Coincidentally, I'm writing logic like this so that no one can manually (through a PanelView screen) energize several outputs on my DeviceNet network and overload the power supply. Why risk a bad situation if you can control it?

 

[geniusintraining]

G,

I have been looking into this lately, (just on a larger scale) you have two options,

1. Limiting the current draw
2. Sizing the breaker

option 1 is up to you if it would be practical and work for your process

option 2 is sizing the breaker should be 125% MIN of FLA (full load amps), 150% is the rule of thumb that some go by

This is a good fourm that covers the NEC (a lot of answers there) http://www.mikeholt.com/code_forum/index.php

I hope my research was correct