Commercial Panels

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George Stolz

Staff member
Windsor, CO NEC: 2017
Service Manager
drg said:
Next time I'll try and get involved with one these system's , for some odd reason I always seem to be doing something else......they don't sound that complicated but something I would like to put my hands on once , that always makes a big difference in understanding for me.
I hear that! There are a lot of things that have been discussed on around here that I am mentally familiar with, but stumble on when it comes time to apply hands to them.


Senior Member
Wilmington, NC
iwire said:
All the ones I have done required an external 120 volt source to trip them.

Same here.

This is why I don't think shunt trips are the "best" means of controlling an emergency situation. You may lose your control circuit and never know it (and unless you are doing some PM or inspections you will only find out when you need it to work and it doesn't).

I used to wire a lot of gasoline pumping stations and I would always use a contactor for the E-Stop control. If you lose your control circuit, the contactor drops out and no gas. You have to fix the control circuit in order for the system to work at all.

This is not code, just my personal preference.


Can you get Shunt trip breakers that require 120V or similar supply all the time? Then if you lost control power the breaker would trip!


Senior Member
We typically use 'Undervoltage Release' instead of 'Shunt Trip' modules when faced with the emergency shutdown issue. That way, loss of power causes the breaker to trip. The downside is you now need to generate control power from a source upstream of your breaker. Sometimes there are no good answers.


Senior Member
South East PA
We often use shunt trips, but usually for larger breakers (1000A), sometimes we also equip them with motor operators (that attach to the front of the breaker). With the motor operator you can open or close the breaker. However, the breaker is typically opened using the shunt trip and closed using the motor operator.
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