It was brought to our attention by an electrical plan reviewer that 2005 NEC 700.27 requires selective coordination on emergency overcurrent devices. Does this mean we will have to submit coordination studies for emergency distribution systems now? How about when a generator feeds an entire building? Will we have to provide a coordination study for the entire building?
Question on 2005 NEC 700.27 Coordination
- Thread starter Bob7135
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ryan_618
Senior Member
- Location
- Salt Lake City, Utah
You would have to have a coordination study for anything that is on the emergency (or legally required standby) system.
bphgravity
Senior Member
- Location
- Florida
This question wouldn't happen to be for a large grocery retailer in SW Florida would it?
It is likely you will need to provide time-current curves along with the coordinated overcurrent device specification details. Consult with your plan reviewer for exact detail, as the amount and type of information that will be required with document submittals will vary. Here in Florida, some only require studies within the recommended guidelines of The Florida Agency for Healthcare Administration (short-time and long-time ranges) while others want coordination all the way to ZERO time (instantaneous range).
It is likely you will need to provide time-current curves along with the coordinated overcurrent device specification details. Consult with your plan reviewer for exact detail, as the amount and type of information that will be required with document submittals will vary. Here in Florida, some only require studies within the recommended guidelines of The Florida Agency for Healthcare Administration (short-time and long-time ranges) while others want coordination all the way to ZERO time (instantaneous range).
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Of course nobody publishes curves to 0 seconds (not even the fuse guys), but this has become a royal pain in the application.
Actually it's not for a grocer, but the fact was brought up by a plans examiner in the Orlando area.
The more I think about it, the term "Selective Coordination" in this context probably means comparing IT curves for just the overcurrent devices, and not doing a full-blown coordination study to include the impedances of the circuits between the OCPD's, such as required by ACHA.
It's probably a good idea to contact our local plan reviewers to see what they are going to require.
The more I think about it, the term "Selective Coordination" in this context probably means comparing IT curves for just the overcurrent devices, and not doing a full-blown coordination study to include the impedances of the circuits between the OCPD's, such as required by ACHA.
It's probably a good idea to contact our local plan reviewers to see what they are going to require.
davidr43229
Senior Member
- Location
- Columbus, Oh
Actually Article 700 for Selective coordination means that all of the OCPD needs to be coordinated (only 1 OCPD actuates) in a fault or overload. This means in the overload region and shortcircuit region (.01) range. You achieve this my overlaying the curves on eachother.
The IT or I^2 T is energy that in 2008NEC per article 240, the ICEA wire withstands ratings have been reintroduced and should be considered when choosing an OCPD.
Just my $.02
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