Grounding and Breaker requirements in an Accessory Structure

[ArtisanFarms]

I am finishing my 30X50 final and forever shop next to a house I am renovating and ran into a few questions from my inspector when he came out to check the electric.

According to the town, the building is considered to be an Accessory Structure. I have built it as a shop building following commercial guidelines and apparently there are some differences between the commercial code and the Accessory Structure requirements. One difference is a requirement for CAFCI breakers and the second may relate to grounding and bonding.

The shop is pole construction with tin walls on the interior. I have wired the entire shop with EMT mounted on the face of the tin. The shop has 150A service and a rotary phase converter for the 3 phase tools. The single phase and three phase circuits are kept in separate EMT runs. My inspector is primarily a residential inspector and after looking at what I had done, said first that the panels were properly bonded and grounded but that he needed to hit the books to refresh his memory on grounding requirements with EMT for a non-commercial structure. He thinks I might need to run a ground wire in my EMT rather than using the EMT as the ground. Has anyone ever heard of or seen this being a requirement? If it is, I have a real problem as some of my runs are filled and to add a ground wire would require either replacing the existing conduit with the next size up, or running additional pipe carrying just the ground wire.

 

[wyliesdiesels]

If the conduit runs are complete from panel to end junction box, then a wire EGC is not required by code.

There is no designation between reaidential and commercial.

Your AHJ, however, may have local WRITTEN amendments, that do not allow the EMT to be used as an EGC.

 

[billconner]

Most electrical engineers do not accept EMT for ECG, but code does.

If that's all he questioned, sounds like a success.

 

[alfredeneuman]

Most electrical engineers do not accept EMT for ECG, but code does.

Most electrical engineers don't specify the type of raceway.

 

[billconner]

Most electrical engineers don't specify the type of raceway.

EMT? Of course they do, or have in my career consulting on the design of 150 or so theatres. Filled with EMT. Almost all with a ground wire.

The only project that used the EMT for ground was a design build project where contractors had a major say, the Texas Trust CU Theatre at Grand Prairie - Grand Prairie TX. (Third or fourth name on the building, hard to keep up.)

 

[alfredeneuman]

Of course they do, or have in my career consulting on the design of 150 or so theatres.

I used to be an estimator/project manager for an electrical firm, had to look at hundreds of sets of prints and in my experience very few call out raceway types. I had all sorts of different conditions unknown to or unaddressed by the engineers to deal with on vastly differing occupancies from factories to amusement parks.
Theaters share the same basic electrical "cores" (projection room, lobby, etc).

 

[sparky 1971]

I am finishing my 30X50 final and forever shop next to a house I am renovating and ran into a few questions from my inspector when he came out to check the electric.

According to the town, the building is considered to be an Accessory Structure. I have built it as a shop building following commercial guidelines and apparently there are some differences between the commercial code and the Accessory Structure requirements. One difference is a requirement for CAFCI breakers and the second may relate to grounding and bonding.

I'd request to see that in writing. I'd say if anything, it would be closest to a garage, and AFCI protection isn't required. If you have a kitchen or sleeping quarters in the shop, that may change things up, but only in those locations.

The shop is pole construction with tin walls on the interior. I have wired the entire shop with EMT mounted on the face of the tin. The shop has 150A service and a rotary phase converter for the 3 phase tools. The single phase and three phase circuits are kept in separate EMT runs. My inspector is primarily a residential inspector and after looking at what I had done, said first that the panels were properly bonded and grounded but that he needed to hit the books to refresh his memory on grounding requirements with EMT for a non-commercial structure. He thinks I might need to run a ground wire in my EMT rather than using the EMT as the ground. Has anyone ever heard of or seen this being a requirement? If it is, I have a real problem as some of my runs are filled and to add a ground wire would require either replacing the existing conduit with the next size up, or running additional pipe carrying just the ground wire.

Wow. I thought everyone, especially inspectors, knew that EMT could serve as a ground. Is he trying to tell you that EMT can be used for a ground in a commercial application but maybe not residential?

 

[billconner]

I used to be an estimator/project manager for an electrical firm, had to look at hundreds of sets of prints and in my experience very few call out raceway types. I had all sorts of different conditions unknown to or unaddressed by the engineers to deal with on vastly differing occupancies from factories to amusement parks.
Theaters share the same basic electrical "cores" (projection room, lobby, etc).

Performing arts theatres, not cinemas.

And you're saying electrical engineers dont specify a ground wire in EMT, when it's not required by code? How come contractors install them then? Must add cost.

 

[alfredeneuman]

I'm not going to get into a ******* contest over this. (AEN, over and out)