EMT grounding

[PoorOwner]

Do I need to pull a ground (THHN/THWN) if using EMT if the first metal box is grounded with a green ground screw?

I think I prefer to pull one though. So at each box the ground wire needs to ground the box and receptacle, right?



also, where it is coming in the first box through the garage wall, (romex) is it acceptable to just wrap the ground wire around the ground screw without cutting it before going to wire nut. Saving some space.

 

[wolfhawk73]

Do I need to pull a ground (THHN/THWN) if using EMT if the first metal box is grounded with a green ground screw?.

Yes.

I think I prefer to pull one though. So at each box the ground wire needs to ground the box and receptacle, right?.

Yes.

also, where it is coming in the first box through the garage wall, (romex) is it acceptable to just wrap the ground wire around the ground screw without cutting it before going to wire nut. Saving some space.

Yes.

At least that's what I did for years, and I doubt the NEC has back-tracked on those requirements since '03.

Don't quote me.

 

[Norcal]

EMT is suitable for grounding also.

 

[sberry]

The first box is bonded with the screw to the service neutral, the second would be bonded thru the conduit provided one didn't use partial knockouts. The second box will need an additional ground bar and if you want run a green or bare wire from service neutral to it. Depending on how many spaces are available in the first box it may save some congestion and ease to add a ground bar to it also, can attach ground rods and grounding conductors it instead of neutral.

 

[mm08822]

The first box is bonded with the screw to the service neutral, the second would be bonded thru the conduit provided one didn't use partial knockouts. The second box will need an additional ground bar and if you want run a green or bare wire from service neutral to it. Depending on how many spaces are available in the first box it may save some congestion and ease to add a ground bar to it also, can attach ground rods and grounding conductors it instead of neutral.

You're talking about panels. OP is talking about boxes in conduit runs for devices.

 

[sberry]

Whoops, I didn't understand. Had it confused with something else.

 

[wyliesdiesels]

Do I need to pull a ground (THHN/THWN) if using EMT if the first metal box is grounded with a green ground screw?

No.

Code allows EMT to be used as the EGC and therefore no additional conduxtor is needed for an EGC.

I think I prefer to pull one though. So at each box the ground wire needs to ground the box and receptacle, right?

If using metal boxes and self grounding outlets then u would only need to ground the box.

also, where it is coming in the first box through the garage wall, (romex) is it acceptable to just wrap the ground wire around the ground screw without cutting it before going to wire nut. Saving some space.

Yes u can do that.

Yes

Incorrect.

Read first comment above...

 

[PoorOwner]

If using metal boxes and self grounding outlets then u would only need to ground the box.

So.. basically the common 15 A receptacle is self grounding?
So no ground wire in the second box, but need pigtail from receptacle TO the box.
Even though you says "self grounding", shouldn't mounting the receptacle to the box itself give me the ground?

I will check the ohms after the job, likely there will be a few ohms but it should be grounded well?

For the pigtailing then.. can I use 14 gauge solid on a 20 amp circuit ( with 12 THHN for hot and neutral)

 

[sberry]

You need to use a 12 but, self grounding is for devices screwed in to the box but if it is mounted in the cover needs a tail. I skip it on a few I have mounted in handy boxes, most of my 4x4 is cover mounted so I can change the configuration some if wanted, its pretty much a personal thing though.

 

[wyliesdiesels]

So.. basically the common 15 A receptacle is self grounding?

Yes but check outlet to be sure.

So no ground wire in the second box, but need pigtail from receptacle TO the box.

Dont need one in first box either.

No pigtail needed IF conduit is continuous metal, panel to box, box is metal, AND outlet is self grounding.

Even though you says "self grounding", shouldn't mounting the receptacle to the box itself give me the ground?

Yes thats what self grounding means. It grounds itself to the box.

For the pigtailing then.. can I use 14 gauge solid on a 20 amp circuit ( with 12 THHN for hot and neutral)

For 15a circuits #14 for EGC, 20a circuits #12 for egc and 30a circuits #10 for egc...

 

[PoorOwner]

OK.. I got it..
it's NOT directly connected to the panel. In the first box, it has a romex 12/2 coming in. So will ground that with a ground screw. Then the 2 wirenut to THHN.

However.. What if the first box has 2 romex (2 circuits) coming in.. it sounds like just need to tie the 2 grounds together and to the first box then?

 

[sberry]

Yes.

 

[ard]

Not all receptacles ARE 'self grounding'.

When one IS self grounding, and has this feature (usually a spring doohicky at the yoke), then it will self ground- no need to attached it to the ground point in the box.

However many (most?) cheap receptacles are NOT self grounding.

At least that is my recollection

 

[PoorOwner]

I will run the pigtail

Just one thing though. I just got the motor switch that is in a metal box with knock outs. The inside and outside of the box are both painted. How would i get a good ground out of this if I don't run a ground wire.
The knock out 2 step. is a 1/2 inside a 3/4 so the retaining nut might not fit that well either

It may make a little contact but I think some sanding is needed for best result

 

[PoorOwner]

I am still not liking the heavily painted , on both side concentric knock outs, apparently you don't need a grounding bushing .. (Lock nut with a clamp for ground wire) until greater than 250V, can anyone confirm.

It doesn't look like for 1/2 KO this is a popular piece either, because who would run 250V+ circuit thru 1/2 KOs. But it seems there is a few pieces available. I would need one on both entrance and exit of the box to get good grounding

 

[sberry]

Lots of higher voltage circuits thru smaller pipe though, a big welder may only need 12 wire at 480 3ph.

 

[wyliesdiesels]

I am still not liking the heavily painted , on both side concentric knock outs, apparently you don't need a grounding bushing .. (Lock nut with a clamp for ground wire) until greater than 250V, can anyone confirm.

It doesn't look like for 1/2 KO this is a popular piece either, because who would run 250V+ circuit thru 1/2 KOs. But it seems there is a few pieces available. I would need one on both entrance and exit of the box to get good grounding

Just scrape the paint off.

And yes bonding bushings are required for 480v not 240v...

U could certainly use one if u wanted to....

 

[grantw]

Just scrape the paint off.

And yes bonding bushings are required for 480v not 240v...

U could certainly use one if u wanted to....

I added a bonding bushing to my 2" EMT that feeds my 40 space sub-panel. I don't trust lock nuts against a painted surface to catch a 200A fault. For the 3/4 emt out of the sub, I have a ground wire. Overkill for home use, but I sleep easier. I guess in 20-30 years, the new owner will also know exactly where ground is just pulling one outlet..?

 

[wyliesdiesels]

I added a bonding bushing to my 2" EMT that feeds my 40 space sub-panel. I don't trust lock nuts against a painted surface to catch a 200A fault. For the 3/4 emt out of the sub, I have a ground wire. Overkill for home use, but I sleep easier. I guess in 20-30 years, the new owner will also know exactly where ground is just pulling one outlet..?

I dont trust good continuity through paint either....even more so if its a concentric knockout with only very minimal contact via the 2 tabs...