Roof penetration

[Punner]

Hi,
I understand that the NEC has "uses not permitted" for flexible cables. I have a situation where a machine is being fed with many flexible cables (power/controls/etc.). The environment and access is prohibitive to mounting a junction box for these cables where the machine is located. How can I mount the junction box on the roof above the machine and still meet code? Can I mount the junction box directly to the roof and use chase pipes to penetrate the roof? Is there some other method?

Thanks,

 

[petersonra]

If it is already hooked up why are you wanting to add a junction box?

 

[hbiss]

The machine is connected with flexible cables now? Do they penetrate the roof or are you wanting to re-route the power and control outside on the roof then come down through to the machine? Or am I completely off base here.

-Hal

 

[Punner]

If it is already hooked up why are you wanting to add a junction box?

Hi, it is not yet hooked up

 

[Punner]

The machine is connected with flexible cables now? Do they penetrate the roof or are you wanting to re-route the power and control outside on the roof then come down through to the machine? Or am I completely off base here.

-Hal

The connection and design is not yet complete. Penetrating the roof will allow the junction box to be outside the environment and allow for easier access. You are correct about the routing though - I want to route the power and control outside on the roof and come down to the machine

 

[kwired]

What you are asking to do is sort of what is often done with waste water lift stations.


More details might be helpful

 

[Punner]

What you are asking to do is sort of what is often done with waste water lift stations.


More details might be helpful

Yes, of course.
So the machine is an overhead crane and will be fed with either a festoon system, or an energy chain system. These systems are what I am wanting to penetrate the roof with. The cables will range from type SOOW to type W.
The location where the system stops is in an area that has no accessibility without building scaffolding, or being creative with suspended platforms - which is another reason not to put the junction box there.
The environment is very dirty and humid - typically 100% humidity, ambient 140 F, somewhat corrosive, etc... The crane is moving ash, leftover from burning waste, and that ash gets all over everything in that area.
Thanks,

 

[Rick 0920]

NEC 400.12 seems to prohibit what you are wanting to do here. Getting special permission from the AHJ may allow you to do this, but I'm not sure.

 

[Punner]

NEC 400.12 seems to prohibit what you are wanting to do here. Getting special permission from the AHJ may allow you to do this, but I'm not sure.

Yes, this is my challenge.

 

[tom baker]

What about a jbox that extends thru the roof? Have it prepped for the crane power connections. Have a removable top to access connections.

 

[Punner]

What about a jbox that extends thru the roof? Have it prepped for the crane power connections. Have a removable top to access connections.

If this is acceptable to meet code, it could definitely be an option.

 

[hbiss]

EC 400.12 seems to prohibit what you are wanting to do here.

Not familiar with 400.12. That's new in the 2020. So what is it and are you on the 2020?

-Hal

 

[Rick 0920]

Hal, NEC Art. 400.12 is "Uses Not Permitted" for flexible cords and flexible cables. It lists (7) different applications in which you cannot use them. I saw a couple that could be used to turn down this type of installation. We are currently in the 2017 Code here in Jacksonville, FL but I am teaching out of the 2020.