Flexible cord usage in a Class 1 Div 1 area

[vectormechanic]

I have been tasked with designing the electrical system for a trailer mounted evacuation system consisting of a 480V 5HP vacuum pump, a 120V 1/4HP water cooling unit, two level switches, a temperature switch, and the controls to run aforementioned motors. The trailer/vacuum pump setup is classified C1D1 (group D) due to the fact that it will be exhausting pentane during operation. It is being trailer mounted in order to be able to use it at any of the plants in our complex.

As this is trailer mounted, it will need to be powered via flexible cord, one cord for 120V control and cooler power and one cord for 480V motor power.

Unfortunately, I am working off the 2002 edition of the code and do not have a newer version handy. Per 501.11, it appears that I can use an extra hard usage cord (STOW) as long as all the conditions of the section are met (although I am confused by how the exception after 501.11 (5) comes into play). This is an industrial installation (geothermal power plant), and qualified electricians will be installing and servicing the installation and the cord will be protected. Where the cord comes into the XP control and motor started boxes, I am planning on using a strain relief CGB installed into a seal fitting.

My questions are this:

1. Am I correctly interpreting the code that I can use the STOW cord to power the setup? If not, what alternatives are there (other than MI or MC-HL)?

2. If I can use the STOW, is it appropriate to bring the cord into the box through the CGB/seal fitting setup?

This is my first time doing any class 1 div 1 stuff, so it is taking quite a bit of time to ensure I get this right. Thanks for the help.

 

[rbalex]

You are basically on the right track. The exception after 501.11(5) is irrelevant in your application since it refers to installations in Division 2.

The STOW is an acceptable cord/cable for your application.

The open item is the ?suitable seal? reference in 501.11(5). Because STOW is a cable under Article 400 as well as a cord, sealing it also falls under 501.5(D). Unfortunately, 501.5(D) deals only with MC-HL or ?cables in conduit.? You application is not addressed directly.

It is usually best to assume the STOW has ?? a gas/vaportight continuous sheath capable of transmitting gases or vapors through the cable core ?? Sealing it in accordance with 501.5(D)(2) would be a ?suitable seal.?

Using a strain relief, such as a CGB, would be consistent with 501.11(3).

Note: All references were to the 2002 NEC. I believe your State is still using that edition. The analysis from the 2005 and 2008 editions is essentially the same.

 

[vectormechanic]

Thanks!

Thanks!

Thanks for the confirmation. As for code edition, Nevada is a hodgepodge with local municipalities adopting edition at different times. Some of the rural counties still don't even require permits for residential construction.

In Washoe County (where Reno is) they are using the 2005 edition with local amendments pending approval.