Is the coordination study required only for emergency system not normal power system? I heard some folks said it is not required for normal power system, but I thought it was but couldn't find reference rules in NEC, can someone help? Was it changed under 2008 edition? Thanks!
Coordination Study - Requirement
- Thread starter anbm
- Start date
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- Location
- Logan, Utah
There is no general requirement for selective coordination of overcurrent protective devices for normal power systems in the NEC. It is a design issue and not a code issue.
Chris
Chris
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
The way the code is worded has to do with overcurrent devices that supply emergency (or legally required standby) loads. Such devices must be selectively coordinated with all upstream overcurrent devices. A normal load that gets power from a normal source would not come under this requirement. See 700.27 and 701.18.
- Location
- Illinois
- Occupation
- retired electrician
Charlie,
It is my opinion that the circuits that feed the "emergency loads" must be selectively cooridinated and to me that includes all of the supply side devices that are upstream of these loads, both on the normal and the emergency systems.
It is my opinion that the circuits that feed the "emergency loads" must be selectively cooridinated and to me that includes all of the supply side devices that are upstream of these loads, both on the normal and the emergency systems.
There is a good article at
http://www.iaei.org/magazine/?p=2105
It confirms that it is needed on the normal side.
Selective coordination is also required for elevators.
http://www.iaei.org/magazine/?p=2105
It confirms that it is needed on the normal side.
Selective coordination is also required for elevators.
skeshesh
Senior Member
- Location
- Los Angeles, Ca
I think Charlie covered that in his response. Am I missing something here?
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Check with the AHJ.
In Wisconsin and Minnesota, they only require selectivity to the first upstream device on the normal supply. Their reasoning is that if the normal source feeder device trips, the condition of the rest of the non-emergency system makes no difference to the emergency circuit.
In Wisconsin and Minnesota, they only require selectivity to the first upstream device on the normal supply. Their reasoning is that if the normal source feeder device trips, the condition of the rest of the non-emergency system makes no difference to the emergency circuit.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I don't think I said anything that would contradict that opinion.
But now I will.
A local rule (statewide, actually) says that they will only enforce coordination for the configuration that is in service when the normal utility power is lost and the backup power source is on line.
- Location
- Illinois
- Occupation
- retired electrician
Charlie,
I misread your original post.
I misread your original post.
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