Piggy backing flexible cords

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I need some help from the technical experts out there. I am an army safety specialist with the McAlester Army Ammunition plant, McAlester, Oklahoma.

Situation: During an annual safety inspection of a facility it was noted that 4 heavy duty flexible cords were piggy backed, connecting a Dayton Air Circ Fan in a Class 1 Div 2 area. We won't go into the last part of that one folks

I had been trained in USAF safety that piggy backing of flexible cords was not permissable IAW the NEC. Once again, we won't discuss the Class 1 Div 2 req's in this msg. LOL I have researched 400-7 and 400-8 which in itself is pretty clear cut.

I was referencing 400-7(b) Attachment plugs. It references 400-7(a)(3), (a)(6), and (a)(8) ... attachment plug being energized directly from a recep outlet.

I don't want to send a customer an incorrect reference without consulting you all. However, am I on track with the way I am reading this?

Please confirm

Thanks folks for your time and knowledge



Staff member
Mission Viejo, CA
Professional Electrical Engineer
Re: Piggy backing flexible cords

Good analysis.

Now, why is it Class I, rather than Class II?
Re: Piggy backing flexible cords

It is Class I Group B due to it being a flammable environment where they heat up the tar and tar coat the bombs versus being in a Class II Group E location loading the explosives mixtures and such.

I didn't know if the new article 406 had any further information as I have not recieved the new code as of yet. I went to a seminar covering the NEC 2002 changes, but that is it as of yet.


Senior Member
Re: Piggy backing flexible cords

If you want an NEC reference, it is 110.3(B), if you want the place to find more info, General Information for Electrical Equipment - the UL 'White Book' - Cord Sets And Power Supply Cords (ELBZ).
Re: Piggy backing flexible cords


Thanks for the information. It didn't occur to at the time to look in there. Appreciate the heads up.
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