# Control panel disconnect for LOTO



## gpop (May 14, 2018)

Osha would require that you recognize the hazard. Nfpa 70E would require the panel to be shut down or a engineered solution be used to reduce the hazard unless you can prove that in doing so may cause a life safety risk / severe damage at which point you would be require to use ppe that covers all known risks.


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## paulengr (Oct 8, 2017)

notanexpert said:


> I have a 480V motor control panel with incident energy at 18" < 1.2 cal. It is fed from a power distribution panel that has incident energy ay 18" > 1.2 cal. After troubleshooting it is determined that a VFD inside the control panel has failed and needs to be replaced.
> The disconnect is installed in the upper right corner, finger-safe, and the line conductors are not exposed anywhere in the panel and only terminate at the disconnect.
> 
> For the purpose of replacing this failed component, can I de-energize the panel using the main disconnect or do I have to go upstream? Is there a code, standard, or OSHA case to prohibit me from using the control panel disconnect?


OSHA makes this all fall under the general duty clause...protect employees from known hazards using industry best practices.

I’ve got news for you: EVERY panel has this issue. The key is look in the DEFINITION of an arc flash hazard in 70E. The key is are you performing a task that MIGHT cause an arcing fault because of something you are doing? This is the rule that applies as far as whether or not you wear appropriate PPE at all or not. This does not include as the 70E committee stated several times “just walking by”. Electrical equipment isn’t inherently dangerous under normal conditions or we could not even use it at all. So opening abs closing the disconnect is obviously normal use and does not require PPE unless for instance the breaker just tripped and needs a quick visual inspection before re-energizing (see NEMA AB-4).

Even if you fell under that category by your description (
OSHA has a rule that you don’t work live unless there is no other option or working live is the safer option. The above case...test before touch, is an example of no other option.

Once proven dead is there anything that you are going to do that could cause an arc flash? Can you inadvertently get into those guarded conductors because of what you are doing? For instance spraying denatured alcohol from a pump sprayer for cleaning? If so then you need to go upstream. Otherwise if it’s LOTO with no way to inadvertently cause an arc flash or get a shock have at it.

You can’t work on most industrial panels, all switchgear, all MCCs, panel boards and switchboards, disconnects, and almost anything else if you don’t recognize that there will always be some part of an enclosure that is still energized 99.9% of the time. You have to recognize the case of inadvertent situations and it is task dependent. For instance fishing wire blindly into that same control panel can cause an inadvertent problem. Open overhead bare wiring in a substation is perfectly safe until you walk in there carrying a stick of conduit over your shoulder.

This is why 70E and NEC have rules for qualified and unqualified people. While replacing a VFD in a panel a rookie on my team decided to teach up and grab around the wiring on top of the breaker for leverage. He survived and only got bit pretty bad. But that’s what I mean by inadvertent contact and why you need to give experienced personnel that would recognize the hazard and never do that from the ones that come around the corner with a water hose washing up the concrete and spraying water in and on everything. That is why rookies need to stay 3.5 feet or more away from an open panel unless you are there and can slap their hands.

VFDs are positively one of the more tricky things to deal with. Normally as mentioned the breaker is hot on top. But more difficult is the control wiring. Often a PLC cannot be de-energized and it may be on a different ground in another remote cabinet, and may cycle voltages because of other interlocks. So testing relay contact voltages doesn’t always work and you can get a shock at 120 or even 240. Even if you avoid this it can blow a teeny hidden control fuse that takes hours to find. Drawings from different vendors is always a challenge. In other words don’t bother and it will be out of date or wrong anyway even in a nuke plant. I just lift one wire at a time on all externally sourced wiring and wire nut every one individually treating them all as energized. No other practical way to do it.


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## SWDweller (Dec 9, 2020)

I was taught to do LOTOTO

Lock out, tag out, try out. 
The guy that added the last step was showing how a complicated machine was properly locked out and hit the start button. Several contactors closed and they all looked like, oh crap. The machine was not going to start but some of the equipment was battery powered. We got a new procedure in about a week. 
Even with the power cord removed, the lift worked, the main computer screen worked and could be trouble shot, and both the radios worked.


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