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Lock MCC Room Doors?

Lock MCC Room Doors?

Lock MCC Room Doors?

Hello all, I'm new here.

I have a somewhat heated situation where one supervisor insists that all MCC (motor control center) room doors must be locked at all times.  Can anyone share some light on this subject?  Does OSHA require that MCC doors be locked at all times?

Here are the details about equipment in a typical MCC room:

- 2300V Metal-Enclosed Switch Gear (no exposed live parts)
- 480V Metal-Enclosed Switch Gear (no exposed live parts)
- All MCC room doors are inside a controlled access industrial building (meaning that Joe Blow, who is unauthorized and unqualified, is not going to wonder into the building, let alone a MCC room)

Most of this discussion seems to revolve around OSHA 1910.303(g).  Any ideas?

RE: Lock MCC Room Doors?

Locks keep honest people honest.  What happens in a situation where a qualified person needs in?  Administravie controls are acceptable by OSHA, telling people to keep out and training them to do such is acceptable.  If a person breaks the entry rule, fire them.  If they get injuried or killed, they have a huge fight in court to win.  Cases have been won where people break in and get injuried, but because they were not warned of the danger, the employer lost.

RE: Lock MCC Room Doors?


This section applies "If live parts operating at more than 600 volts are located within the room or space, unless:

The live parts are enclosed within grounded, metal-enclosed equipment whose only openings are designed so that foreign objects inserted in these openings will be deflected from energized parts, or

The live parts are installed at a height above ground and any other working surface that provides protection at the voltage to which they are energized corresponding to the protection provided by an 8-foot height at 50 volts.

(u)(4)(ii)The rooms and spaces shall be so enclosed within fences, screens, partitions, or walls as to minimize the possibility that unqualified persons will enter.

(u)(4)(iii)Signs warning unqualified persons to keep out shall be displayed at entrances to the rooms and spaces.

(u)(4)(iv) Entrances to rooms and spaces that are not under the observation of an attendant shall be kept locked.

(u)(4)(v) Unqualified persons may not enter the rooms or spaces while the electric supply lines or equipment are energized.

RE: Lock MCC Room Doors?

Thank you for your help.  I'll keep digging.

RE: Lock MCC Room Doors?

(not based in the US, so no expert on OSHA)

An option would be to use keyed access with a push-bar on the inside, to allow safe egress in an emergency. An alternative to that would be to use a maglock and only give access to "suitably qualified" personnel that way.

Reading the regs quoted above, they seem to be there to prevent unauthorised operation of the equipment. Lockable cabinets would be another way of further controlling this.

If you need to allow "access" for unqualified personnel to perform rounds & readings for example, then perhaps cages or similar visible access might be suitable.


RE: Lock MCC Room Doors?

Our production line runs 24/7/365 but I do not schedule my E&I guys for nights, only day shift.  The major concern about locking the doors is that when an E&I guy gets called in at 2AM for a trouble-call, he will be working alone in the MCC room behind locked doors.  This situation is of great concern.  My job is to keep my guys safe and locking the doors when OSHA does not require it is unacceptable to me.  Especially when there has been no historical issue with unauthorized/unqualified people entering the MCC room.

I just don't see the requirement to lock the doors in the NFPA or the NEC Code for our application.  Am I right or am I wrong?

RE: Lock MCC Room Doors?


(u)(4)(iv) Entrances to rooms and spaces that are not under the observation of an attendant shall be kept locked.

From above, once your guys are in there, it doesn't need to be locked. That would be my interpretation of it. Check that your lone worker procedures address their operations, just as a back-up for them.


RE: Lock MCC Room Doors?

Our MCC rooms are absolutely locked and only trained and authorised people who know what they are doing have keys for access.

In the event that someone is called out and could be working on their own then our operators are trained to accompany them re what basic safety rules they need to know before any work is done on or inside any panels and basic rescue requirements should something go wrong.

RE: Lock MCC Room Doors?

The new OSHA statndar (Subpart S) that goes into effect on 8/13/07 clarifies this a little more in 1910.303 (g) and (h)

RE: Lock MCC Room Doors?

Thanks to Zogzog, this is what I found:

Installations accessible to unqualified persons. Electrical installations that are open to unqualified persons shall be made with metal-enclosed equipment or shall be enclosed in a vault or in an area, access to which is controlled by a lock. If metal-enclosed equipment is installed so that the bottom of the enclosure is less than 8 feet above the floor, the door or cover shall be kept locked. Metal-enclosed switchgear, unit substations, transformers, pull boxes, connection boxes, and other similar associated equipment shall be marked with appropriate caution signs. If equipment is exposed to physical damage from vehicular traffic, suitable guards shall be provided to prevent such damage. Ventilating or similar openings in metal-enclosed equipment shall be designed so that foreign objects inserted through these openings will be deflected from energized parts.

From this, it appears that the room itself does not need to be locked but there is a possibility from the wording that the "door or cover" needs to be "locked".  From my experience, when OSHA says "locked" they mean that the use of a tool must be used to gain access.  Anyone have further info on what OSHA considers "locked?"

RE: Lock MCC Room Doors?

OSHA defines a LOTO lock requirements as able to withstand 50 lbs of downward force, thats the best I can do for you there.

RE: Lock MCC Room Doors?

That looks like the old standard, did you check the newest revision that was released 2/14/07?

RE: Lock MCC Room Doors?

I just got off the phone with an Inspector at our local OSHA office.  He states that the doors leading to the MCC room DO NOT NEED TO BE LOCKED, as long as there are no exposed live parts and all enclosures are metal-clad and their doors/covers are locked closed.  He defined "locked" as requiring a tool OR key to gain access. I specifically asked if a cabinet that requires only a screw driver to open it is considered "locked" and he said YES.  He said the intent of the statute is to discourage unauthorized access, not to stop access, because stopping someone that is determined in not possible (you can't protect the stupid from them selves . . .).

He said the same interpretation applies to electrical enclosures that are out on the plant floor, for example, a control cabinet for a machine.  Those enclosures do not need a pad lock on them, just some form of locking mechanism that requires a tool to bypass the door interlock so it may be opened.

Thank you everyone for your input.  Looks like I finally got the answer I was looking for.  Now, since I am on the OSHA radar, I'll just sit here and wait for the surprise inspection.  And the OSHA inspector says, "Lets see, $7500 per violation X per person X per day X per scratch my butt, ah, yes your total fine is one billion dollars . . . will that be credit or debit?"  

RE: Lock MCC Room Doors?

What state are you in Valancelectron?

RE: Lock MCC Room Doors?

Las Vegas, Nevada.

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