Vibration isolation

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kentirwin

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Norfolk, VA
Okay, I don't know if it comes from years of "doing it this way" or not and I can't quickly find an NEC reference (2002). Normally when running EMT or RMC to a motor I convert to flexible conduit for the last couple of feet or so for vibration isolation. Currently there is a contractor onsite (industrial site) providing power for an enclosed 75hp compressor. There is a wiring/controller cabinet in the compressor enclosure that is not in direct physical contact with the compressor motor itself. The contractor is using EMT all the way into the conduit entrance. While this is not direct entrance to the motor itself, I'm still used to converting to flex for the conduit entry as the entire compressor/enclosure is subject to vibration. And yes, the compressor/enclosure assembly is anchored to the concrete floor. So my question - can anyone provide a code reference that would posibly prohibit this? Thanks in advance. :)
 
Re: Vibration isolation

I did a search for "vibration" and only found references in busways, fire pumps, manufactured homes and rec. vehicles, and for flexible cords, and also appliances.

Nothing specific to your problem. I also tried searching for "flexible", but that returned a million hits.

Steve
 
Re: Vibration isolation

Ahh, so you are looking for something that would prohibit "hard piping" to vibrating machinery.

Only thing I can think of might be 358.12(1) for EMT.

-Hal
 
Re: Vibration isolation

Ahh, didn't think of that. I tend to read the instructions only as a last resort. ;) I'll search out the manufacturer's documentation this morning. Thanks.
 
Re: Vibration isolation

Well, the documentation just makes a broad statement about electrical installation "per NEC and any local standard..."
 
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