Grounding lug dual or single rated ?

[Mehmetuygur]

What is it that I should be looking for to identify whether a grounding lug is rated for dual ground wires ?

Also, I have a 400 amp overhead service for a multi family unit. Dual 4/0 aluminums coming thru a 2.5" emt riser. Do I need a grounding bushing on any part ? At the moment I have it so that my water main ground and the ground rid earth ground come together in the main cabinet and both connect at a dual lug. That lug is bonded to the neutral bus as well.

And does it it matter if you use copper water bonding clamps with aluminum wire or should I stick with aluminum clamps ?

 

[tom baker]

First, the term "ground" is not defined NEC term. I think you are referring to a GEC, right?
Do you want to terminate two GECs in the same lug, probably won't find any lugs that will allow that, but you would check the mfgs instructions.

Can you run the conductor thru the lug? So one long conductor going to each panel with the lug in the middle.
Or use two lugs



Service raceways need to be bonded per 250.94

Just an FYI in Washington we are not allow to use EMT for service raceways.

 

[Carultch]

What is it that I should be looking for to identify whether a grounding lug is rated for dual ground wires ?

Also, I have a 400 amp overhead service for a multi family unit. Dual 4/0 aluminums coming thru a 2.5" emt riser. Do I need a grounding bushing on any part ? At the moment I have it so that my water main ground and the ground rid earth ground come together in the main cabinet and both connect at a dual lug. That lug is bonded to the neutral bus as well.

And does it it matter if you use copper water bonding clamps with aluminum wire or should I stick with aluminum clamps ?

A lug is only rated for 1 wire, unless listed otherwise. Generally, lugs for 2 wires will either have two lug positions, or have a lug profile that is shaped like a snowman.

As for the copper vs aluminum issue, your terminations need to be listed for use with whichever wire you are using. And if you are using both wire materials in the same termination device, you need physical separation between them. Copper bodied terminations are generally only compatible with copper wire, while aluminum bodied terminations (usually tin coated) might be compatible with either. The reason is thermal expansion, since copper expands more than aluminum, so a copper wire will tighten an aluminum lug, while an aluminum wire will loosen a copper lug with heating.