Steel building electrical ground

[Yotaforce]

I'm putting in the conduit and wiring now in my all steel building. Can I wire the ground directly to each outlet box, which is mounted to the metal beams? It only makes sense considering the building is grounded to the rebar in the foundation and the breaker box is grounded to the building and the ground rod. Any one know anything about this? I am interested because I could run more wires through my 1/2" conduit and run less conduit for each circuit.

 

[filthy]

What does your building code say about it?

 

[MXtras]

The NEC allows you to run the ground through the conduit for circuits up to a certain amperage. For normal circuits, it if fine to use the conduit (EMT or rigid) for the ground. Not the neutral but the safety ground.

I am not sure about using the building frame as the ground, but the conduit is allowed.

I am sure WCummings will be along any minute to clear all this up for us.

Scott

 

[Yotaforce]

They are all 20amp circuits and yes, I meant using the conduit as ground, but considering it is all strapped to the frame, I refer to it being grounded to the building.

 

[kbs2244]

Go to 3/4 pipe.
It doesn’t cost that much more and it makes pulling the wire a whole lot easier.
The pipe will be the ground all the way back to the box. The fact that it is screwed to a grounded support is nice, but it isn't a replacement.
Your local inspector will tell you how many hots can share a neutral.

 

[MXtras]

I was also going to suggest the 3/4" upgrade, but opted not to say anything.

I wired up my commercial shop myself and ran 1/2 to all the outlet boxes and overhead lights and that was fine, but any runs to machines or welders, do yourself a favor and run 3/4" or larger. Even though the NEC has maximums for conduit fill, they are tough to work unless all of the wire is pulled at once. Snaking an extra circuit through after it's in place ***** big time.

If I do any of this in the future, I will run 3/4".

Scott

 

[Yotaforce]

Well, I would, but I allready ran my 1/2" conduit, and when it came time to run the circuit for the lights, I thaught I would just yank the extra three wires through the same run to keep from having to run another conduit line. Not too big a deal, but would allow me to move on to next step.

 

[johansonp]

I'm new around here, but I was an electrical contractor in a previous life so I thought I'd chime in.

You can certainly use the conduit as the circuit ground. My personal preference is to run a grounding conductor if possible, but what you are proposing is perfectly fine.

You'll just want to pay extra attention to tightening the conduit connectors, especially if you are going to install an interior finish on the walls.

Thanks and hello,

Paul

 

[chevytruck]

Too many hot wires in one conduit can cause overheating. the rule in the code book is three current carrying conductors before you have to derate the amps. to keep heat down. The way your grounding will work but my preference would be to pull a seperate ground wire. In case a connector comes lose or something else that breaks the conduit apart.

 

[MXtras]

...my preference would be to pull a seperate ground wire.

That's likely the "best" way to go. I do not disagree. But in many cases, the runs are so long and so numerous that saving the cost of just one wire per circuit can add up to a substantial amount of money.

In my case using the conduit as a ground for my lighting and outlet circuits alone saved me about $1200 and in my opinion, it is perfectly safe when done properly.

I am not bashing - I am just giving a reason for the apparent 'economy' approach. Some might think it's an unsafe shortcut.

Scott

 

[Yotaforce]

Thanks guys. I went on ahead and pulled ground wires and made another run of conduit for my lighting circuit. Not too bad. I had my 8 year old daughter help me out.