Why is SER ground so large

[Rex Hungerford]

I have a subpanel I am installing in a residence in Arizona. I was going to feed it with SER style cable. Copper 1/0-1/0-1/0. When I look at all the SER cable, the bare ground is #2. Why. When I look at 250.66, 250.102(c)(1) or 250.122 the largest ground required is #6.

Can I use something such as a Encore Tray Cable that has a #6 ground.

https://encorewire-prod.imgix.net/media/products/product-sheets/copper/industrial/EncoreWire_CU-Tray-Cable-Power-THHN.pdf

The issue I have is the ground bar holes accept #4 max. For my own reasons, I don't want to drop a aluminum lug on top of the ground bar to accept the larger wire. I want to use one of the holes in the copper bar. And I don't see why all the ground are so large.
Thanks

 

[infinity]

I have a subpanel I am installing in a residence in Arizona. I was going to feed it with SER style cable. Copper 1/0-1/0-1/0. When I look at all the SER cable, the bare ground is #2. Why. When I look at 250.66, 250.102(c)(1) or 250.122 the largest ground required is #6.

What size OCPD is protecting the sub-panel feeder?

 

[tom baker]

There are adapters for ground bars to allow a larger wire, “chair” is the trade lingo

 

[infinity]

Oversized EGC's in a cable can be larger when needed for parallel condcutors or 250.122(B).

 

[Electromatic]

The bare conductor is sized as a reduced-size neutral for service applications (hence, S.ervice E.ntrance cable): 3 hots & a neutral

 

[Rex Hungerford]

An Encore engineer said a UL standard requires all grounds in SER to be no less than 2 sizes smaller. I will run pipe and wire.

 

[LarryFine]

Of course, the pipe can be the EGC if it's metallic.

 

[Electrical 4 me]

I have asked myself the same question and came to the conclusion presented above by Electromatic. Also pull a ground wire. Don't rely upon the conduit to be your EGC unless you are using Rigid or IMC and utilizing grounding bushings. I personally cannot believe that EMT is still recognized as a grounding means.

 

[LarryFine]

I personally cannot believe that EMT is still recognized as a grounding means.

It has been documented that even EMT, properly made up, is a better EGC than a wire sized for the conductors the EMT would be sized to contain.

 

[Electrical 4 me]

I have seen too many times throughout my career where EMT used as a EGC has failed over time. It is not worth forgoing the use of an EGC wire to save money while sacrificing safety. I will never be convinced otherwise.

 

[LarryFine]

I will never be convinced otherwise.

Not trying to. It's your choice.

 

[Chamuit]

Do you need to comply with 336.10.9 and use TC-ER-JP?

 

[Chamuit]

Not trying to. It's your choice.

Larry's right.

You also need to check your local amendments if there are any.

City of Phoenix NEC amendments - page 4

250.118.4 Electrical metallic tubing with an additional equipment grounding conductor.

https://www.phoenix.gov/pddsite/Documents/2017%20National%20Electric%20Code%20(NEC)%202018%20Phoenix%20Amendments.pdf

 

[hillbilly1]

It has been documented that even EMT, Properly made up, is a better EGC than a wire sized for the conductors the EMT would be sized to contain.

That’s the key, unfortunately it’s not more often than is.

 

[Tulsa Electrician]

Pic of an add a lug.

 

[ActionDave]

I have seen too many times throughout my career where EMT used as a EGC has failed over time. It is not worth forgoing the use of an EGC wire to save money while sacrificing safety. I will never be convinced otherwise.

Failed over time how? Do you mean that you have seen faulted circuits sitting there energized?

 

[hillbilly1]

I’ve repaired emt drops to the racks in the big box stores, over the years, some have actually energized the racks. Forklifts would hit it and pop it out of the coupling, then short against the coupling on the stub, energizing the rack it was attached to. Since the neutral was not compromised, it didn’t fault and remained energized.

 

[LarryFine]

I’ve repaired emt drops to the racks in the big box stores, over the years, some have actually energized the racks. Forklifts would hit it and pop it out of the coupling, then short against the coupling on the stub, energizing the rack it was attached to. Since the neutral was not compromised, it didn’t fault and remained energized.

That may be a mis-application, but not a fault (no pun intended) of the EMT wiring method itself.

 

[jaggedben]

That may be a mis-application, but not a fault (no pun intended) of the EMT wiring method itself.

EMT is not allowed where subject to physical damage?

 

[LarryFine]

EMT is not allowed where subject to physical damage?

As a tubing, I think it's protection requirements are more like those of NM and MC than of conduit.