Required Grounding Bushings??

[Another C10]

Interesting, I am running a #6 THHN grounding conductor

Its required in california to use a bonding bushing regardless for when bonding a cold water or electrode conductor before landing onto the main panels return buss.

 

[jimport]

Its required in california to use a bonding bushing regardless for when bonding a cold water or electrode conductor before landing onto the main panels return buss.

Do you know the reasoning?

 

[texie]

Its required in california to use a bonding bushing regardless for when bonding a cold water or electrode conductor before landing onto the main panels return buss.

I think you are referring to GEC installation which is not related to the OP. Please see 250.64 (E) and let us know if this makes sense. Note that if the GEC is in raceway is nonmetallic or non ferrous no bushing would be required.

 

[texie]

Do you know the reasoning?

This known as the choke effect that occurs under high current such as lightning which creates a high impedance when a single conductor is enclosed in a ferrous raceway. Hence the requirements in 250.64(E). This is unrelated to the voltage rating of the service.

 

[Another C10]

Do you know the reasoning?

Not really, other than what texie mentioned which sounds pretty good.
To me my true reasoning for such a requirement is to assure a solid bond in the event of a massive surge, without the ground bushing there is more of a chance of a faulty protective bond of the metal enclosure. Although a loose bushing lug screw sort of defeats the bond bushings full potential as well.

 

[Jpflex]

I am installing a new sub-panel for my Ham radio room. It is a 100 amp 240/120 Square D QO panel. I am running less than 25 feet of metallic liquid tight 1" conduit between the main electrical panel and new sub-panel. Question is regarding the need to install grounding bushings on each end of the liquid tight conduit connectors? I have searched the 2020 NEC and I cannot find anything. I thought at one time it was required for ampacity OVER 100 amps. Any thoughts on this?? Thanks

I think the codes you are looking for is the one requiring grounding bushings when voltage is over 277 volts phase to phase but not standard 240 volts or 120 phase to neutral?