Outlet grounded but . . .can't find the ground?

[ckadams00]

I have an outlet in my shop wired from the panel. With a tester it says it is wired correctly, but I cannot find a ground wire; nothing attached to the green outlet screw or the box. This outlet feeds a second outlet through conduit and the second outlet says it has an open ground. Both are the same outlet style (ie the first in not an older two prong).

Any thoughts? I'm trying to fix the ground in the second outlet, but not sure the best approach.

I should also mention the second outlet then feeds two switches - one for an outside light, and one to turn the power to the outlets on - just didn't want to complicate things. . . .

 

[n8n]

If it's run in pipe and it's an older installation, the pipe itself is the ground and there likely wasn't a separate ground wire run through the conduit. If it's a short run I'd go ahead and run a ground wire through the pipe from the 1st to the 2nd recep. Use same gauge green THHN as the current carrying conductors. Connect to back of box @ 1st receptacle and to back of box at 2nd but just wrap wire around box ground screw & then also connect it to the ground screw on the recep.

Have you checked to see if the second *box* is grounded? If this was old school ground through pipe wiring and the original installation had "spec grade" self-grounding receps and then the 2nd recep was later replaced with a builder grade non-self-grounding one and/or things got corroded over time, the 2nd recep may not be making a good connection to ground from the yoke through the box screws to the box, but the box might still have a decent ground connection through the pipe. I prefer to use spec grade for everything and go ahead and put the ground pigtail in anyway (belt and suspenders approach.)

If this is old enough that there's no separate ground wire you'll probably run into the situation that there's not a tapped hole in the box for the ground either, you'll have to drill and tap it yourself... I want to say it's 8-32

if it is at all possible I'd also run a ground back to the ground bus at the panel, but be very careful with that... I'd push the wire from the panel to the recep if at all possible because I'm sure you can imagine what can happen if you do it the other way and contact a bus bar when it finally gets there...

 

[wyliesdiesels]

^^^

If the pipe is metalic and the outlet is self grounding then the outlet is grounded via the pipe and box...

What kind of pipe do u have between first and second box?

 

[ckadams00]

Yep the first receptacle is connected to the service panel with metal conduit. Between the first receptacle and second I have armored cable but I will use the grounding wire between the two boxes.

 

[n8n]

if it's AC a.k.a. BX or even Greenfield (looks the same but is sold without wires in it as "flexible conduit") you've got an uphill battle trying to shove another conductor through it. (proper AC should have a bonding strip inside so it grounds just like pipe)

How long is the run? Might be worth it just to replace with a new run of modern AC or pipe/THHN rather than try to shove wire through old Greenfield.

 

[teamextreme]

If it's run in pipe and it's an older installation....
If this was old school ground through pipe wiring.....
If this is old enough that there's no separate ground wire....

...you'll have to drill and tap it yourself... I want to say it's 8-32

Why do you keep referring to this grounding method as "old"? It's still a perfectly code compliant way of grounding and done all the time.
Also, ground screws are 10-32, FYI.

 

[wyliesdiesels]

if it's AC a.k.a. BX or even Greenfield (looks the same but is sold without wires in it as "flexible conduit") you've got an uphill battle trying to shove another conductor through it. (proper AC should have a bonding strip inside so it grounds just like pipe)

How long is the run? Might be worth it just to replace with a new run of modern AC or pipe/THHN rather than try to shove wire through old Greenfield.

Code no longer allows grounding via bonding wires or the metal jacket of FMC...he will need a separate EGC like u said..

 

[ckadams00]

if it's AC a.k.a. BX or even Greenfield (looks the same but is sold without wires in it as "flexible conduit") you've got an uphill battle trying to shove another conductor through it. (proper AC should have a bonding strip inside so it grounds just like pipe)

How long is the run? Might be worth it just to replace with a new run of modern AC or pipe/THHN rather than try to shove wire through old Greenfield.

The metal conduit is not flexible. I am not comfortable running a ground wire back through it to the service panel (I'm not comfortable with anything having to do with a service panel). So: if the conduit/box/first receptacle is grounded, can I simply run ground wires to the rest of the outlets? From what I understand the first outlet is probably grounded to the box/conduit through the screws . . .the ground screw doesn't have anything on it. I could tie the ground screw to the outlet box as an extra measure, and then tie in other ground wires that run to the other outlets.

My other outlets are connected with flexible conduit, so grounding them to their boxes doesn't seem like an acceptable solution?

 

[n8n]

The metal conduit is not flexible. I am not comfortable running a ground wire back through it to the service panel (I'm not comfortable with anything having to do with a service panel). So: if the conduit/box/first receptacle is grounded, can I simply run ground wires to the rest of the outlets? From what I understand the first outlet is probably grounded to the box/conduit through the screws . . .the ground screw doesn't have anything on it. I could tie the ground screw to the outlet box as an extra measure, and then tie in other ground wires that run to the other outlets.

My other outlets are connected with flexible conduit, so grounding them to their boxes doesn't seem like an acceptable solution?

If you have a good solid ground (will it light a 200W light bulb? I've thought about making up a short cord with the neutral and ground swapped for testing grounds with even higher draw devices) then yes, that's not the way it'd be done today, but you'll be fine.

I'd personally buy a roll of new AC and rerun the BX/Greenfield runs; the time/aggravation savings will be worth the extra cost.

I'd also look into having a more experienced friend run a ground through the pipe back to the service panel just for peace of mind, if you have such a friend, but as I said if the existing ground is solid that is optional. Were this being installed today a separate green wire would be run alongside the current carrying conductors however.

 

[Wirepuller]

Install a gfi at the first receptacle. Load to everything else.

 

[ckadams00]

Install a gfi at the first receptacle. Load to everything else.

Wirepuller, sorry to be dumb but with electricity I'd like to think there are no dumb questions, just dead people:

When you say GFI at the first receptacle, which is "first:" the one nearest the panel or the one at the end of the line nearest the switch?

So it turns out that in Chicago conduit is acceptable as a ground. Regardless, I have a ground wire between the receptacle closest to the panel (which is grounded through non-flexible conduit) and the switch, with everything pigtailed to a ground screw at each box.

 

[Wirepuller]

First, as in first device after the panel. The feed if you will. It's code compliant to use a 3 prong receptacle on a 2 wire system without a grounding conductor. Eliminates the need to pull new wire or a new ground. Fastest, cheapest, best way to do it without adding conductors.

 

[Wirepuller]

Wirepuller, sorry to be dumb but with electricity I'd like to think there are no dumb questions, just dead people:

When you say GFI at the first receptacle, which is "first:" the one nearest the panel or the one at the end of the line nearest the switch?

So it turns out that in Chicago conduit is acceptable as a ground. Regardless, I have a ground wire between the receptacle closest to the panel (which is grounded through non-flexible conduit) and the switch, with everything pigtailed to a ground screw at each box.

If there isn't a grounding conductor in the conduit and it's only relying on the conduit itself I wouldn't ground the box to the device with anything unless its emt or rigid. You're going to be sending fault current through this.

A problem I often see is when someone adds a 3 prong grounded receptacle on a older two wire system and uses a jumper to a metal box. You're potentially sending fault current through this. Where is it going next? I don't know. Unless its all being done in emt or rigid I don't recommend using conduit as a grounding conductor, in some states using conduit as a grounding conductor is not allowed anymore. Bad practice. Using a gfi allows the removal of the misused jumper it is the safer and the recommended practice.

 

[ckadams00]

Done & everything tests correct! Thanks for all the input!

 

[wyliesdiesels]

If there isn't a grounding conductor in the conduit and it's only relying on the conduit itself I wouldn't ground the box to the device with anything unless its emt or rigid. You're going to be sending fault current through this.

A problem I often see is when someone adds a 3 prong grounded receptacle on a older two wire system and uses a jumper to a metal box. You're potentially sending fault current through this. Where is it going next? I don't know. Unless its all being done in emt or rigid I don't recommend using conduit as a grounding conductor, in some states using conduit as a grounding conductor is not allowed anymore. Bad practice. Using a gfi allows the removal of the misused jumper it is the safer and the recommended practice.

really? I have never heard of this...Do u have a reference to this? Conduit, other than AC/BX and MC, is a code compliant method for EGCs. Why do u think its bad practice? And whats wrong with fault current flowing on conduit?

 

[Wirepuller]

Sorry. Should have said its a mass amendment as well as a few other states I can't recall exactly which ones. Fault current flowing through an unknown path is always a bad ide.

 

[wyliesdiesels]

Sorry. Should have said its a mass amendment as well as a few other states I can't recall exactly which ones. Fault current flowing through an unknown path is always a bad ide.

But the path isnt unknown...