Bonding conduit

[Nathan Hoggatt]

I am wanting to know if I need to bond my 3/4 inch conduit.

The only wire in it is a 1/0 ground. There are no current carrying conductors in the conduit.
It is the grounding system for a 400 amp service in a commercial building.

The purpose of the conduit is to protect the ground wire from abuse as it is in an unsecured area subject to potential vandalism.

 

[iwire]

If the conduit containing the GEC is ferrous metal then yes you must bond the conduit to the GEC.

See 250.64(E) for the fine details

When you run a single isolated conductor in a ferrous conduit and then apply a strong current to the conductor as would happen during a fault the combination of the single conductor and ferrous conduit raises the imdeance of the circuit.

By bonding the conduit to the GEC at each end you make the conduit and conductor act as a single conductor.

 

[Carultch]

If the conduit containing the GEC is ferrous metal then yes you must bond the conduit to the GEC.

See 250.64(E) for the fine details

When you run a single isolated conductor in a ferrous conduit and then apply a strong current to the conductor as would happen during a fault the combination of the single conductor and ferrous conduit raises the imdeance of the circuit.

By bonding the conduit to the GEC at each end you make the conduit and conductor act as a single conductor.

What if it is metallic conduit, but non-ferrous, like aluminum conduit?

 

[MasterTheNEC]

What if it is metallic conduit, but non-ferrous, like aluminum conduit?

Non-ferrous metal raceways are not required to made continuous....and does not require the same connections.

 

[tom baker]

Bonding the Al conduit would lower the impedance, due to lightning is high frequency and tends to travel on the skin of the conductor. Information on why we bond metallic conduits for a GEC is in the IEE Green Book

 

[MasterTheNEC]

Bonding the Al conduit would lower the impedance, due to lightning is high frequency and tends to travel on the skin of the conductor. Information on why we bond metallic conduits for a GEC is in the IEE Green Book

Doing and Requiring are two different beasts.....

 

[Electricalartist]

Any conduit installed,when conductive, must have a means to trip the breaker if a current carrying conductor comes in contact with it. Emt will remain energized in the event of a fault unless bonded

 

[iwire]

Any conduit installed,when conductive, must have a means to trip the breaker if a current carrying conductor comes in contact with it. Emt will remain energized in the event of a fault unless bonded

However in most cases just a standard connector and lock nut do that job.


In the case of an EGC are required to do more bonding than that.

 

[Carultch]

In the case of a [GEC] you are required to do more bonding than that.

Corrected

 

[iwire]

Corrected

Thank you.

 

[Electricalartist]

Corrected

Right in the case of a grounding electrode conductor ran in a emt pipe, both ends of the pipe have to be bonded and the bond jumper can not be smaller than the gec. This has to do with induction and choking. Most of the current will choked .

 

[Nathan Hoggatt]

So would using a 3/4" bonding bushing be permissible in the panel alone or does it need to be at both ends of the conduit?

 

[Nathan Hoggatt]

Or can I increase the size of the lug on the 3/4" bushing to accommodate the 1/0 wire size?

 

[Carultch]

So would using a 3/4" bonding bushing be permissible in the panel alone or does it need to be at both ends of the conduit?

In general, it only needs to happen on one end, unless you are using it as the EGC.

In the special case of the GEC, it needs to happen on both ends. It doesn't necessarily need to be a bonding bushing, as a bonding U-bolt or other external pipe bonding clamp/strap could also suffice.

 

[Nathan Hoggatt]

Thanks for the info guys.