OSHA Requirements for Junction Boxes

[bward]

A client has recently run into some trouble with their safety inspector and I'm trying to figure out a solution that will allow them to continue working.

They had been installing branch circuit wiring onto the load side of breakers in a switchboard. The breakers they were making connections to were properly turned off and locked out, but the neighboring ones were not. The line sides of the breakers are continuously covered, but the load sides remain exposed. Since this work is in a datacenter-type environment, turning off all the breakers is unacceptable. The inspector has forbidden them from doing this type of work unless the power to all the breakers has been disconnected.

I am trying to devise a solution where each breaker's load side is connected to a dead-front terminal block. The load terminal of the breakers can remain enclosed, and all wiring connections will be made at the terminal block. Since the terminal block is dead-front, there are no "exposed" live conductors. The terminals that will be worked on will be disconnected as per normal.

I've tried to research the OSHA rules on working in live panels, but I can't seem to find anything saying that working near "unexposed" live conductors in a box is okay. Does anyone here know if this might be acceptable? Does a dead-front terminal block actually satisfy the requirements for covering a live conductor?

Thanks.

 

[iwire]

Web search OSHA 1910.333

Live parts that an employee shall be exposed to shall be deenergized.

By the way if this panel is part of a PDU the fault current can be very high.

 

[bward]

And 1910.339 defines:

Exposed. (As applied to live parts.) Capable of being inadvertently touched or approached nearer than a safe distance by a person. It is applied to parts not suitably guarded, isolated, or insulated. (See Accessible and Concealed.)

Guarded. Covered, shielded, fenced, enclosed, or otherwise protected by means of suitable covers, casings, barriers, rails, screens, mats, or platforms to remove the likelihood of approach to a point of danger or contact by persons or objects.

Isolated. (As applied to location.) Not readily accessible to persons unless special means for access are used.

Insulated. Separated from other conducting surfaces by a dielectric (including air space) offering a high resistance to the passage of current.

Conductor --
(3) Insulated. A conductor encased within material of composition and thickness that is recognized by this subpart as electrical insulation.

Using the first definition, the fact that the wire is insulated and the conductive parts of the terminal block are guarded by their covers would lead me to believe that my proposed solution would be acceptable. I just have never seen it done before in this kind of situation, so I'm trying to get some feedback on it.

 

[pfalcon]

... Since this work is in a datacenter-type environment, turning off all the breakers is unacceptable. ...

I work with IT people. Lots of things are unacceptable to them but especially spending money. Data centers - when done properly - are redundant. That means two separate wiring systems. You should be able to shut off one whole box while the other half of the data center operates. The server for ABC should be on one supply while the "mirror" server should be on the second, separate supply. Don't forget to alternate the lights as well.

 

[pfalcon]

Using the first definition, the fact that the wire is insulated and the conductive parts of the terminal block are guarded by their covers would lead me to believe that my proposed solution would be acceptable. I just have never seen it done before in this kind of situation, so I'm trying to get some feedback on it.

All of our electrical panels use insulated conductors with finger-safe protection at all terminations. Lockout is still required. During mechanical work on a panel wires can accidently work lose.

 

[iwire]

Using the first definition, the fact that the wire is insulated and the conductive parts of the terminal block are guarded by their covers would lead me to believe that my proposed solution would be acceptable. I just have never seen it done before in this kind of situation, so I'm trying to get some feedback on it.

I understand exactly what you are up against, I have been in the exact same situation in data centers.


My own opinion is your terminal block plan still has issues with compliance.

 

[bward]

Thanks for the comments guys.

They don't like spending money to the point where the main power supply and the backup power supply are coming from this same panel - just 2 different breakers... Not a problem I'm going to worry about though.


I suppose if I think there _might_ be an issue with the terminal blocks idea, then an OSHA inspector _will_ have an issue with it.