NEC 110.26(5)

anbm

Senior Member
NEC 2017 - 110.26 (5) Separation from High-Voltage Equipment.
Where switches, cutouts, or other equipment operating at 1000 volts,
nominal, or less are installed in a vault, room, or enclosure
where there are exposed live parts or exposed wiring operating
over 1000 volts,
nominal, the high-voltage equipment shall be
effectively separated from the space occupied by the low
voltage equipment by a suitable partition, fence, or screen.

What is considered exposed live part for this new rule in NEC 2017? Can a substation (15kV primary, 480/277V secondary, 500kVA, 3PH xfmr)
be located in the same room with other low voltage panels (480V, 208V) as long as clearances are met? Or the substation needs to have its own room?
Thank you!
 

xptpcrewx

Power System Engineer
Location
Las Vegas, Nevada, USA
Occupation
Licensed Electrical Engineer, Licensed Electrical Contractor, Certified Master Electrician
NEC 2017 - 110.26 (5) Separation from High-Voltage Equipment.
Where switches, cutouts, or other equipment operating at 1000 volts,
nominal, or less are installed in a vault, room, or enclosure
where there are exposed live parts or exposed wiring operating
over 1000 volts,
nominal, the high-voltage equipment shall be
effectively separated from the space occupied by the low
voltage equipment by a suitable partition, fence, or screen.

What is considered exposed live part for this new rule in NEC 2017? Can a substation (15kV primary, 480/277V secondary, 500kVA, 3PH xfmr)
be located in the same room with other low voltage panels (480V, 208V) as long as clearances are met? Or the substation needs to have its own room?
Thank you!
Article 100 contains the definition for "Exposed (as applied to live parts). Yes you can have LV equipment in the same room as a substation, what do you think the 480Y/277-V transformer secondary and its associated equipment/devices are?
 

Carultch

Senior Member
Location
Massachusetts
Article 100 contains the definition for "Exposed (as applied to live parts). Yes you can have LV equipment in the same room as a substation, what do you think the 480Y/277-V transformer secondary and its associated equipment/devices are?

Would equipment that is normally covered by a deadfront, be considered "exposed live parts" in this rule? I.e. live parts that are only exposed during maintenance, and otherwise concealed inside an equipment housing.

110.26(A)(1) uses the term "exposed live parts" in a context where it would make more sense if it said "exposable live parts". 110.26(A)(1) still applies to equipment with all live parts covered by a deadfront.
 

xptpcrewx

Power System Engineer
Location
Las Vegas, Nevada, USA
Occupation
Licensed Electrical Engineer, Licensed Electrical Contractor, Certified Master Electrician
Would equipment that is normally covered by a deadfront, be considered "exposed live parts" in this rule? I.e. live parts that are only exposed during maintenance, and otherwise concealed inside an equipment housing.

110.26(A)(1) uses the term "exposed live parts" in a context where it would make more sense if it said "exposable live parts". 110.26(A)(1) still applies to equipment with all live parts covered by a deadfront.
Interesting observation... Never noticed this before.

I would think so since 110.26(A) parent language is about working space for the purposes of examination, adjustment, servicing or maintenance while energized.

Also, there is an informational note after the definition that would suggest any live parts that are not suitably guarded, isolated or insulated.
 
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