Bonding Flex Conduit

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johnjeremy

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I have EMT coming out of a 480/277V Panel it changes over to flex two feet away from a 75kva transformer and has a 90 deg. connector terminated in the side of the transformer. My question is does the conduit have to have grounding bushings inside the transformer and panel even though the flex and fittings is listed for grounding???
 
Re: Bonding Flex Conduit

Yes, a bonding bushing would be a good idea. To insure a good ground fault path, the bushing would bond the metal parts of the transformer.
Of course, if there is an EGC run with the ungrounded conductors then the bond would be insured. :)
 
Re: Bonding Flex Conduit

Thank you I have been told that it is not required but have always done it. So I was just curious from a code standpoint. I guess I have always been wrong.
 
Re: Bonding Flex Conduit

I have always ran a grounding conductor through it and bonded the ends as 340.60 seem's to require it.


348.60 Grounding and Bonding.
Where used to connect equipment where flexibility is required, an equipment grounding conductor shall be installed.
Where required or installed, equipment grounding conductors shall be installed in accordance with 250.134(B).
Where required or installed, equipment bonding jumpers shall be installed in accordance with 250.102.
 
Re: Bonding Flex Conduit

Note that the UL Guide Information (DXUZ) for flexible metal conduit says:
Flexible metal conduit no longer than six ft and containing circuit conductors protected by overcurrent devices rated at 20 amps or less is suitable as a grounding means.
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Also note that the listing information for flexible conduit fittings restricts the use of these fittings for grounding purposes if the overcurrent protective device is greater than 20 amps.
Flexible Metal Conduit Fittings ? Flexible metal conduit fittings designed for connection to the conduit by clamping around the circumference of the conduit are considered suitable for grounding for use in circuits over and under 250 V and when used in accordance with the NEC and containing conductors protected by overcurrent devices rated 20 A or less. Flexible metal conduit fittings of types other than the clamping type mentioned previously in the 3/8 through 3/4 in. trade size and containing conductors protected by overcurrent devices rated 20 A or less are considered suitable for grounding when used in accordance with the NEC. All other trade sizes that have been investigated for grounding are marked "GRND" or the equivalent.
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The flexible metal conduit and its fittings are not suitable for use as an EGC in this application. A bonding conductor around the flexible conduit is required. The bonding conductor can be internal or external to the flexible conduit. The flexible conduit connector will require a bonding bushing only if the connector is installed in a concentric or ecentric knockout that still has rings remaining.
Don

[ October 06, 2003, 09:44 AM: Message edited by: don_resqcapt19 ]
 
Re: Bonding Flex Conduit

Thanks Don.

You have cleared methods or bonding up for me also for flexible conduit.
 
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