selective coordination

[Grouch]

Hey all,
Is there a difference between being coordinated and being 'selectively coordinated'? All I can find in articles is selective coordination. I have 2 breakers whose time current curves overlap in an area, but i'm being told that it is acceptable since they are coordinated... they don't have to be selectively coordinated. What is the difference?

Thanks.

 

[dkidd]

Hey all,
Is there a difference between being coordinated and being 'selectively coordinated'? All I can find in articles is selective coordination. I have 2 breakers whose time current curves overlap in an area, but i'm being told that it is acceptable since they are coordinated... they don't have to be selectively coordinated. What is the difference?

Thanks.

I can't imagine anyone seriously telling you that. I seem to recall that the Code was changed to be explicit because someone thought that there was a difference.

 

[ron]

The definition in the code (2014) is
Coordination (Selective). Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.

Selective coordination requirements include emergency systems, legally required standby systems, and critical operations power systems in 700.28, 701.27, and 708.54, respectively.
Requirements for selective coordination for elevator feeders are in 620.62.

In 517.30(G), coordination is required only for faults that exceed 0.1 second in duration.

As you can see in 517.30(G), there is a difference between "selective coordination" and just "coordination"

Some local jurisdictions have amended the code allowing "coordination" for several of the load types.

 

[Grouch]

The definition in the code (2014) is
Coordination (Selective). Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the selection and installation of overcurrent protective devices and their ratings or settings for the full range of available overcurrents, from overload to the maximum available fault current, and for the full range of overcurrent protective device opening times associated with those overcurrents.

Selective coordination requirements include emergency systems, legally required standby systems, and critical operations power systems in 700.28, 701.27, and 708.54, respectively.
Requirements for selective coordination for elevator feeders are in 620.62.

In 517.30(G), coordination is required only for faults that exceed 0.1 second in duration.

As you can see in 517.30(G), there is a difference between "selective coordination" and just "coordination"

Some local jurisdictions have amended the code allowing "coordination" for several of the load types.

Thanks Ron.... ok, I think I got it...

For healthcare facilities, you only need the devices for the essential electrical system to be 'coordinated' for any faults that last for more than 0.1 seconds. So by coordination, we mean only faults lasting greater than 0.1 seconds.

For other facilities (non-healthcare), you need the devices for emergency systems, legally required, COPS, and elevators to be 'selectively coordinated', for the entire time range. So by selective coordination, we mean faults that last for any time period (greater and less than 0.1 seconds).

This is a basic question, but does selective coordination need to be applied to normal power circuits? It would appear that it doesn't apply. Also, I thought healthcare facilities had to be selectively coordinated for all time ranges, not just greater than 0.1 seconds.

 

[ron]

This is a basic question, but does selective coordination need to be applied to normal power circuits? It would appear that it doesn't apply.

Regular circuits do not require any type of device coordination, but you can provide it if you like.

 

[Grouch]

Regular circuits do not require any type of device coordination, but you can provide it if you like.

Got it. What about healthcare facilities though? I was under the impression that OCPD devices for their essential systems had to be selectively coordinated for the full time range... not just coordinated for anything above 0.1 seconds.

 

[ron]

Got it. What about healthcare facilities though? I was under the impression that OCPD devices for their essential systems had to be selectively coordinated for the full time range... not just coordinated for anything above 0.1 seconds.

In NEC-2014: 517.30(G), coordination is required only for faults that exceed 0.1 second in duration. That is Essential systems.

Prior to that, the language was not as clear (although hospitals is not my focus)

 

[dkidd]

In NEC-2014: 517.30(G), coordination is required only for faults that exceed 0.1 second in duration. That is Essential systems.

Prior to that, the language was not as clear (although hospitals is not my focus)

The language was added to match that in NFPA 99.