Nfpa 70e

[kellytshort]

I have a generator room and was wanting to set the Instantenous portion very high right before .5s to coordinate better with my downstream devices and the alternative to that is very high arc flash. So here is my thought I tie the door contacts and motion sensor for the room into the instantenous portion of the circuit breakers. My thought is while nobody is in the room then arc flash is irrelevant.

My concern is while somebody's in the room and the generators aren't on therefore the instaneous portion is on and the generators fire up I just have to coordinate any inrush with my temporary instaneous.

Any other concerns I am missing?

 

[kingpb]

My gut feeling says, I don't know if this is a good way to do it, although I will have to say it is creative.

If you did do it, I would want some type of reassurance that it was working properly otherwise if your sensor fails, you don't have the protection you thought you did and you end up with someone in room with a false sense of security. Possibly some type of indicating light that says the Instantaneous is engaged. You would also need signage to tell the person to look for the indicating light.

People are installing switches on switchgear that will switch in instantaneous settings. I have only seen this on MV swgr using relays that have multiple tripping group schemes/scenarios. SEL relays are popular for this.

 

[ron]

Is the breaker listed for multiple settings?
If so, it is generally okay to activate it with any type of dry contact.

 

[SG-1]

I agree with kingpb that an indicator light is needed. You may also want to install redundent door sensors.

We call the switch on medium voltage gear used to switch to the sensative settings a maintance switch.

 

[kellytshort]

Yeah thanks for the advice that's what I am doing. I have thermal detection, carbon monoxide, door contacts, motion sensor. red warning lights on when the room is not in instantenous and green when it people are in.

 

[SG-1]

I have only seen this on MV swgr using relays that have multiple tripping group schemes/scenarios. SEL relays are popular for this.

CH has lower end relays that are built into some of their MV breakers that can do this.

 

[zog]

Yeah thanks for the advice that's what I am doing. I have thermal detection, carbon monoxide, door contacts, motion sensor. red warning lights on when the room is not in instantenous and green when it people are in.

I have about 50 breakers in my shop right now that we are retrofitting with newer trip units that use maintenence settings via a padlockable switch. Just flip the switch before interacting with the switchgear to lower your arc flash hazard. Nothing new, we do it every day and have been doing it for 10 years.Much simplier than your plan and a proven method,