Breaker for Skid
Breaker for Skid
(OP)
Industrial plants have packaged skids, which have some motors and some other non-motor loads like lighting, chemical loads, etc. These skids have their own local distribution panels which have individual breakers for each motor and non-motor load. In ETAP these skids are modeled as "static loads", and it is possible to group the loads by type: for example 80% motor-load and 20% non-motor load.
We have to supply the feeder from MCC to a skid, the skid has 80% motor-load and 20% non-motor load. How should we size this breaker (in MCC) for this feeder; should it be sized for 100% motor load, or for 100% non-motor load? Thanks.
We have to supply the feeder from MCC to a skid, the skid has 80% motor-load and 20% non-motor load. How should we size this breaker (in MCC) for this feeder; should it be sized for 100% motor load, or for 100% non-motor load? Thanks.






RE: Breaker for Skid
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Breaker for Skid
RE: Breaker for Skid
So in essence, this means the breaker sizing for an individual load within a "skid" has virtually no direct relationship with the sizing of a feeder breaker for the entire skid. That feeder must protect the CONDUCTORS that are going to the skid, and you will see that the rules for sizing the feeder breaker will align with the rules for sizing the minimum conductor size for that feeder. It could then very well be that if you did end up with a situation where the feeder CB ends up sized to be smaller than the motor branch breaker, that you might end up with nuisance trips happening on that feeder breaker. That's where a "coordination study" comes in handy, to avoid unpleasant surprises.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington