Do I need to ground Metal Junction Boxes?

[Bolson32]

Title, mostly.

I recently ran a sub and rewired my garage using PVC conduit with metal Junction boxes...I know I know....it's not EMT but I didn't have the time or frankly the want to deal with EMT. 5 year garage at most.

Now to the meat and potatoes of the question...should these junction boxes be tied to the ground with a pigtail? I'm not sure if that's practice where people run romex to metal or not. Theoretically if you have a loose wire couldn't the junction box become hot and a potential shock hazard?

 

[pattenp]

Metal boxes where splices and devices exist need to be grounded.

 

[Norcal]

Metal boxes where splices and devices exist need to be grounded.

Metal boxes need to be bonded to the grounding conductor. If it was a metallic conduit, then the above quote applies.

 

[wyliesdiesels]

Yes!

 

[Bolson32]

Okay, so just a pigtail to the screw and then wired in with the ground should work right?

 

[Norcal]

Okay, so just a pigtail to the screw and then wired in with the ground should work right?

As long as your not using a sheet metal screw.

 

[Bolson32]

As long as your not using a sheet metal screw.

Guessing it needs a ground screw?

Sent from my SM-G935V using Tapatalk

 

[pattenp]

Metal boxes need to be bonded to the grounding conductor. If it was a metallic conduit, then the above quote applies.

When I said grounded, I meant the equipment ground wire of the circuit needs to be connected to the box. So how is bonding the box with the EGC not grounding the box?

 

[Norcal]

When I said grounded, I meant the equipment ground wire of the circuit needs to be connected to the box. So how is bonding the box with the EGC not grounding the box?

You were saying where splices or devices exist, a metal box / enclosure used with a non-metallic raceway needs to grounded PERIOD.

 

[wyliesdiesels]

Yeah, a metal box that is not connected via metallic raceway, is isolated and can become accidently energized creating a shock potential.

Whther there are splices or devices in the box does not change the bonding requirement.

 

[pattenp]

Yeah, a metal box that is not connected via metallic raceway, is isolated and can become accidently energized creating a shock potential.

Whther there are splices or devices in the box does not change the bonding requirement.

Thanks for saying it the way you did because Norcal's first response had me confused about my answer. I understand all metal boxes need bonding. I was precisely responding to the OP's comment about possible loose connections in a junction box. I didn't mean to imply that metal boxes with splices or devices are the only boxes that needed bonding. I know what I'm talking about, sometimes I just don't type it out in a clear answer.

 

[matt_i]

If you use the 4" square metal boxes, some styles have a dimple in the stamping which is already tapped 10-32. Which is the perfect size for the "preassembled ground pigtail". I like the stranded ones which I can only seem to find at Menards.

Here's an example.

 

[dscheidt]

Guessing it needs a ground screw?

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NEC requires two complete threads of the screw in the box. Metal boxes are, at minimum and almost universally, 1/16 of an inch thick, which means a 32 tpi screw. Most metal boxes have a tapped 10-32 hole for grounding. On boxes intended for surface mounting, it's raised, on other boxes, it's not. You do not need to use a special screw, just one that's properly made. You may, if you wish, do so. (They're cheap.)

 

[ticklechicken]

I like the stranded ones which I can only seem to find at Menards.

I get them on amazon
https://smile.amazon.com/gp/product/B001524H6A/ref=ox_sc_sfl_title_27?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

 

[Bolson32]

Thanks guys, this is super helpful. I happen to live about a half mile from Menards so I'll just snag some of them.

https://www.menards.com/main/electr...079-c-6447.htm?tid=5341787876174135556&ipos=2

Cheaper than Amazon anyway.

 

[prostreetamx]

Some inspectors actually want the screw also to be painted green so a normal screw will fit but still not be correct. Grounding pigtails already have a green screw.

 

[davetulk]

I use these:

https://www.amazon.com/dp/B00CDVJA0A/?tag=atomicindus08-20

Can buy local home depot or lowes as well. I know not stranded but does come with the green screw already attached and ready to go....if you have a lot of boxes to do saves a little time. Especially with my fat fingers the wire holds the screw in place lol

 

[tab2]

I use these:

https://www.amazon.com/dp/B00CDVJA0A/?tag=atomicindus08-20

Can buy local home depot or lowes as well. I know not stranded but does come with the green screw already attached and ready to go....if you have a lot of boxes to do saves a little time. Especially with my fat fingers the wire holds the screw in place lol

These are what I see on site (and permanently borrow from the electricians when I need some at home).

 

[zmaxmotorsports]

:

Metal boxes where splices and devices exist need to be grounded.