service drop vs. bus drop

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Kevin Davis

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As electrical safety coordinator for our manufacturing plant, I have been asked to seek clarification on the definition of service drops vs. bus drops. Our busways run along the ceiling on the production floor. We have circuits that go from fused bus plugs through EMT to junction boxes, then drop from these boxes through a kellems grip to a disconnect above a workstation or appliance. We use hard service flexible cord for the drops. Are these drops considered 'bus drops' according to Article 368.56, or service drops according to Article 230 section II? Do we need to use a tension take-up support device at the junction boxes? Voltage is below 600V.
 
Re: service drop vs. bus drop

What you are discribing is a branch from a busway as permitted in 368.56.

A service drop as described in 230 part II is an over head service drop on the exterior of a building to the service disconnecting means.

When using flexible cord as a drop make sure you check out 400.7 and 400.8 as 368.56(B) makes reference to. These sections talk about uses permitted and not permitted for flexible cords.

Chris
 
Re: service drop vs. bus drop

Thanks for the reply, Chris. We had already reviewed 400.7 & 400.8 and we're OK with those requirements.
 
Re: service drop vs. bus drop

In the NEC, Service means ?The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served.? The use of Service Drop in the Kellems catalog is not in conflict, as they?re describing a specific product. As defined there, Service drops are ?Light duty to support service entrance cable.? Many folks who don?t work with, or pay attention to, the NEC do not pick out that term as having a specific meaning; shop floor usage. Talking about THOSE items in THAT shop, I myself call these things simply Drops, to avoid confusing other terms such as Bus Drops, Power Cords, Outlets?
Do we need to support? we went through the plant in 1999 to comply with 368.8. This is very clearly shown in my 2002 NEC Handbook. That?s the section enforced locally here. Your situation may be different.
 
Re: service drop vs. bus drop

Thanks for the comments, Peteo. We started focusing on electrical safety last year. In the process of raising awareness we're finding things that need to be addressed, such as these drops. I've already told our Maintenance supervisor that we need to install the tension take-up supports.

We got the NEC handbook for the first time this year (2005 ed.), and it's been a big help.
 
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