Dook Interlock - Industrial control panels - Always needed on all doors?

[Marco Tacchini]

NFPA 79 states that:
"6.2.3 Enclosure Interlocking. When required by 5.3.1.4, each disconnecting means mounted within or adjacent to a controlenclosure that contains live parts operating at 50 volts ac (rms value) or 60 volts dc or more shall be mechanically or electrically
interlocked, or both, with the control enclosure doors so that none of the doors open unless the power is disconnected".
In case inside my panel all "live pars" cannot be touched using the "Jointed Test Finger", can I conclude that my panel does not contain live parts and therefore I shuld not mechanically or electrically interlock all doors? THKS!

 

[Jraef]

NFPA 79 states that:
"6.2.3 Enclosure Interlocking. When required by 5.3.1.4, each disconnecting means mounted within or adjacent to a controlenclosure that contains live parts operating at 50 volts ac (rms value) or 60 volts dc or more shall be mechanically or electrically
interlocked, or both, with the control enclosure doors so that none of the doors open unless the power is disconnected".
In case inside my panel all "live pars" cannot be touched using the "Jointed Test Finger", can I conclude that my panel does not contain live parts and therefore I shuld not mechanically or electrically interlock all doors? THKS!

The Jointed Test Finger as it relates to COMPONENTS is part of the IEC regulations, which are MENTIONED in NFPA 79 Annex E, but are not actually part of it.

Annex E Device and Component Designations
This annex is not a part of the requirements of this NFPA document
but is included for informational purposes only

The mention of Jointed Test Finger in NFPA 79 only comes in under 6.2.2.1 where it refers to access from OUTSIDE of the enclosure, essentially to provide a degree of protection when there must be openings for things like cooling fans etc. "Finger Safe" as it relates to IEC compliance of components INSIDE of the enclosure means nothing with regard to NFPA 79 and door interlocking. Bottom line, you must interlock.

 

[steve66]

What does 5.3.1.4 say?

 

[Jraef]

What does 5.3.1.4 say?

Basically the same thing as 6.2.3, just saying that you need to supply it.

5.3.1.4 Supply circuit disconnecting means mounted within
or adjacent to the control enclosure shall be interlocked with
the control enclosure in accordance with 6.2.3. Where the
supply circuit disconnecting means is not adjacent to the control
enclosure, or where the supply disconnecting means is an
attachment plug and receptacle, a tool shall be required to
open the control enclosure door and a label shall be attached
to that door warning of dangerous voltage inside and advising
disconnection of the power before opening.