grounding metal boxes

[ldcrosby]

A building is wired using EMT conduit from the panelboard to each receptacle box and an equipment grounding conductor is also installed. Article 250.148 (C) requires the equipment grounding conductor to be connected to the metal box by means of a grounding screw or a listed grounding device. Contractor installed self grounding receptacles and connected the grounding conductor to the receptacle, not the box. Does this meet code.

 

[LarryFine]

Re: grounding metal boxes

Yes, if by "self-grounding", you're referring to contact-assuring mounting-screw devices.

Plus, the box is grounded via the EMT.

[ October 31, 2005, 12:05 PM: Message edited by: LarryFine ]

 

[peter d]

Re: grounding metal boxes

Originally posted by ldcrosby:
Contractor installed self grounding receptacles and connected the grounding conductor to the receptacle, not the box. Does this meet code.

No. The EGC must be bonded to the box.

Larry, the fact that the box is grounded via the EMT doesn't relieve us from bonding the ECC to the box in this situation. 250.148 (A)

Now, what we are allowed to do is omit the jumper from the EGC to each receptacle, if self-grounding receptacles are being used. 250.146(B)

Edit: add code references

[ October 31, 2005, 12:13 PM: Message edited by: peter d ]

 

[ldcrosby]

Re: grounding metal boxes

Does article 250.148 care if the box is grounded by EMT. I believe it still requires the equip grounding conductor to be connected to the box under the circumstances given. I guess the question is, is a self grounding receptacle a "listed grounding device" that can be used to connect the equipment ground to the metal box as required by 250.148 (C). Article 250.146 (B) talks about a self grounding recptacle being used to ground the receptacle from a grounded box, not the other way around.

 

[peter d]

Re: grounding metal boxes

Originally posted by ldcrosby:
I believe it still requires the equip grounding conductor to be connected to the box under the circumstances given.

You are correct. You are also correct about the self-grounding receptacle. It can not be used to bond the EGC to the box, but rather bond the receptacle to the EGC. The first connection is made to the box. You can omit the jumper to a self-grounding receptacle, or in the case of a regular receptacle, you connect a jumper from the EGC, to the box and to the receptacle.

 

[peter]

Re: grounding metal boxes

Quote: "Article 250.146 (B) talks about a self grounding recptacle being used to ground the receptacle from a grounded box, not the other way around."

Bow why wouldn't it work the other way. This is unfair. Doesn't electricity go both ways? Do the electrons care?
~Peter

 

[peter d]

Re: grounding metal boxes

Originally posted by peter:


Bow why wouldn't it work the other way. This is unfair. Doesn't electricity go both ways? Do the electrons care?
~Peter

Yes, electrically the connection is the same. The bottom line if an EGC is run, it must meet the requirements of 250.148. We can't rely on a device for EGC continuity, and that includes the connection to the box.