Junction Boxes and interlocks

[testsubject]

Hi all,

Recently, I had to segregate a large enclosure between AC and DC and interlock the AC Doors. I started thinking should this be applied to junction boxes as well.

One of the reasons to interlock the doors is to prevent the casual person from opening the door and accessing live voltage.

Our junction boxes have the motors wired inside them. Should they be interlocked as well since there could be 480VAC available at the terminal blocks?

This is more of a thought experiment but wondered if anyone else came across this.

 

[DarrylR]

No "interlocks" as such. We simply have ordinary locks on all our junction boxes to keep the curious out.


Nice quote by the way...

 

[joseph_e2]

I've only seen door interlocks on boxes that maintenance would be expected to regularly open while energized. J-boxes are typically just labelled with the voltage and a high voltage warning and require tools to open. The tooled opening keeps "casual" folks from wandering into danger. You do have to put some effort into getting zapped.



This is in a manufacturing environment with a detailed LOTO plan that has a zero-tolerance enforcement policy.

 

[cardosocea]

I think the difference is the level of effort required to open a panel door (one lock, so 90 to 180 degree turn). to a JB that will have at least 4 bolts holding it shut.

From experience, most standards about this simply refer to "the use of a tool". Although a panel key could be considered that.

Never thought about this, but you could always swap the JB bolts from hex or philips to whatever standard Apple and others use on their products. That would definitely keep even more people out.

 

[OdinIII]

Hopefully this isn't OT for the OP's question but I've been told that in the US there is no "rule or reg" that requires a lock or tool as minimum equipment to open an electrical panel. I doubted this but then was unable to find anything from OSHA supporting this requirement.

Anyone know exactly what the minimum requirement is for securing industrial control panels up to 600VAC with exposed terminals inside? Different for unexposed terminals?

For the OP, we have a few machines that have interlock switches on the control panel doors that trip the disconnect. I'm not exactly sure how the OEM expects us to troubleshoot this equipment. It seems impossible to me without bypassing the switches.

 

[mobil1syn]

ive had customers require plexiglass covers so the wiring terminals were not accessible. it was one of their internal ways to add an additional layer of effort to keep people from messing with stuff.

 

[testsubject]

Thanks everyone. I did forget about "the use of a tool" standard. That will probably be enough for me.

 

[Slwagner73]

We have installed plexiglass covers to "Protect the curious"...

I fail every safety quiz, because I still believe in the "selective survival of the species" mentality.

 

[cardosocea]

I doubted this but then was unable to find anything from OSHA supporting this requirement.

I'm not in the States and never dealt with OSHA, but this kind of thing would be covered under the risk assessment of the company. OSHA would pick up on the people doing the risk assessment knowingly accepting this or being incompetent at their job not to recognise this as a risk.

 

[dummy_bit]

ive had customers require plexiglass covers so the wiring terminals were not accessible. it was one of their internal ways to add an additional layer of effort to keep people from messing with stuff.

Obviously those will be lost the first time maintenance has to "troubleshoot." About the same as wireway covers

 

[dogleg43]

I thought in either the NEC or NFPA there was a statement about needing a tool to open aan enclosure and a reqular screwdriver was acceptable.

The word “tool” may not have been used but that is the intent.

Also, don’t give these agencies any ideas. It’s tough enough to do electrical work as it is.