Is Bond bushing required?

[carnes51214]

We are installing 480v A/c disconnects. From disconnect to A/C we are using sealtight flex. One side is concentric and the other is not. We do have a equipment grnd in flex. My question is being 480v do I still have to put a bond bushing on the concentric side even if I'm using a equipment grnd conductor. Or is it actually required on both ends because sealtight metallic is not suitable for equipment bonding as is emt and rigid.

Another question on similiar lines is I have a 1 1/2 greenfield flex from panel with is no concentric knock out but to disconnect on bus duct is concentric. Do I need bond bushings on both ends or just the end with concentric knock outs.Also 480 volts.

 

[augie47]

We are installing 480v A/c disconnects. From disconnect to A/C we are using sealtight flex. One side is concentric and the other is not. We do have a equipment grnd in flex. My question is being 480v do I still have to put a bond bushing on the concentric side even if I'm using a equipment grnd conductor. Or is it actually required on both ends because sealtight metallic is not suitable for equipment bonding as is emt and rigid.
.

In my opinon, you do not. The EGC takes care of grounding the unit and the flex is properly grounded on one end.

Another question on similiar lines is I have a 1 1/2 greenfield flex from panel with is no concentric knock out but to disconnect on bus duct is concentric. Do I need bond bushings on both ends or just the end with concentric knock outs.Also 480 volts.

Do you have an EGC also ? what amperage circuits ?

 

[carnes51214]

25 amp 3 phase 480 volt. So being that you have a EGC you do not have to use bond bushings on either end. Wheither concentric or single Knock out. But if I did not have a EGC then I would have to use the bond bushing. Is this correct?

 

[Dennis Alwon]

I believe art. 250.97 comes into play here. From the 2011

250.97 Bonding for Over 250 Volts. For circuits of over 250 volts to ground, the electrical continuity of metal raceways and cables with metal sheaths that contain any conductor other than service conductors shall be ensured by one or more of the methods specified for services in 250.92(B), except for (B)(1).
Exception: Where oversized, concentric, or eccentric knockouts are not encountered, or where a box or enclosure with concentric or eccentric knockouts is listed to provide a reliable bonding connection, the following methods shall bepermitted:
(1) Threadless couplings and connectors for cables with metal sheaths
(2) Two locknuts, on rigid metal conduit or intermediate metal conduit, one inside and one outside of boxes and cabinets
(3) Fittings with shoulders that seat firmly against the box or cabinet, such as electrical metallic tubing connectors, flexible metal conduit connectors, and cable connectors, with one locknut on the inside of boxes and cabinets
(4) Listed fittings

 

[Dennis Alwon]

25 amp 3 phase 480 volt. So being that you have a EGC you do not have to use bond bushings on either end. Wheither concentric or single Knock out. But if I did not have a EGC then I would have to use the bond bushing. Is this correct?

I don't think that is correct. Look at 250.118 (5). An egc must be used in circuits over 20 amps.

 

[Danger32]

If it's 1/2" liquidtight flexible metallic conduit then it can only be used for an equipment ground on up to 20 amp circuits. Wouldn't this essentially leave the flex connector on the end with the concentric K.O.'s unbonded?