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Interlocking Electrical Enclosures

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bigdog

Electrical
May 31, 2001
21
I am working on a project that has one main electrical, and four sub-enclosures. The main houses the main disconnect and fuses. In the sub-enclosures theres fusing for the enclosure and motor controls (motor starters).
My question is this; in the main enclosure the disconnet interlocks the door (it's a shaft style disconnect), but in the sub-enclosures the disconnect does not interlock the door(s). So, is it required that the door(s) be interlocked?
 
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Excuse the short answer. The doors cannot be opened by unqualified personnel with the power on. So you have two choices. A door interlocking system typical of Rittal enclosures or a electrically operated door switch in the other doors that do not allow the doors to be opened when the circuit breaker is closed. Usually on the electrical door interlocks, a keyswitch is included that defeats the electrical door interlock so service personnel can open the doors without first removing power.
 
Evem though the sub-enclosures are single door (NEMA12) with latches. In other words it takes a tool open the door.
 
Suggestion: General answer: It depends what is inside the subenclosure in relationship to the upstream and/or downstream electrical installation and loads.
 
Not sure if the same is true in the US but here in Euroland the doors do not need to be interlocked if all the equipment inside is designed to prevent accidental touch i.e IP20 "finger proof".
 
I was unaware you could omit the iterlocking in Euroland if every thing was "Finger Proof." But I am unsure exactly what it would take to make Everything finger proof. Looks like a cost trade off analysis.

In the US if you are going to carry 460 through out the enclosures, which you seem to indicate by saying motor you have motor starters in them, you have to interlock. I do not believe a special tool eliminates this. Rittal has a special key to open their doors yet they are still interlocked. And do forget the assortment of warning signs you are required to use.
 
Nice discussion.

In our plant, we have key switches that can bypass guard switches (schmersal)of any electrical panel. Only qualified personnel has this "universal key". This is important when troubleshooting the panel or the machine specially if the application is critical or that can destroy product being run.

dydt
 
Where is this interlock requirement from? Not from the National Electric code, then where?
 
Sorry for the late post. Try NFPA 79 (2002 Ed) Chapter 5.3 - 5.5 for clarification on this. 5.3.1.4 discusses the tool/warning scenario.
 
(cont) Not only am I late, but sloppy in my posting. NFPA 79 Chapter 6 also covers your interlocking question
 
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