Metal Garage Electrical Service

[Joshua5438]

Would this be a good clamp to use for attaching ground wire to ground rod?

 

[wwhitney]

Probably, my only hesitation is that it says "rebar" ground clamp, but I don't see why it would be any different for a ground rod or a pipe. The important thing is that it is direct burial rated. Assuming you use an 8' ground rod, the entire ground rod needs to be driven into the soil, so the connection will be buried as well.

Cheers, Wayne

 

[Sponsor]

 

[Joshua5438]

Online states grounding rod, rebar and pipe. I think it will be better than the oval ones but that's just me. Haha.

Next questions -

Should the building bond tie into the main panel ground bar, main panel neutral bar or the ground rod?

Power company here likes the ground wire to go from the rods to the meter can. Do I need to run a ground wire from the meter can to the main panel or does that create a parallel path?

 

[wwhitney]

Definitely no wire-type grounds between meter can and the service disconnect. Although as discussed, if you use metal conduit between them that ends up as a ground in parallel to the neutral, since the neutral is bonded to both enclosures. That's fine if possibly nicer to avoid.

Your earth electrodes get connected to the service neutral at the service disconnect or upstream of it, so if your POCO prefers them in the meter can, that's fine.

Bonding structural metal is governed by NEC 250.104(C) which says you can connect to any of the options you listed. Not sure if just mounting the service disconnect enclosure or the meter can to the structural metal is itself enough, or if you need an explicit wire-type bond. And of course, if both the meter can and the service disconnect enclosure are bonded to the structural metal, then the structural metal also becomes a parallel path to the service neutral conductor. Which is apparently fine.

Cheers, Wayne

 

[Joshua5438]

Thanks! I will run a #4cu from the main panel ground bar to the building.

 

[wwhitney]

That jumper gets sized by Table 250.102(C)(1), which goes by the size of the ungrounded conductors. So #4 Cu is good for up to 3/0 Cu or 250 kcmil Al. I didn't review the thread to see what you are using.

Cheers, Wayne

 

[Joshua5438]

I am using 3/0cu from meter to panel. I hope it isn't referring to what the PoCo will use as I have no clue what that will be.

 

[wwhitney]

I am using 3/0cu from meter to panel. I hope it isn't referring to what the PoCo will use as I have no clue what that will be.

No, definitely the conductors after the service point, not those under control of the POCO. They are likely to use something a fair amount smaller.

Cheers, Wayne

 

[Joshua5438]

Any idea if the bond in the bottom right will suffice? If not, I could move it to the big lug at the bottom of the right neutral bar.

 

[wwhitney]

Item one on the list in 250.104(C) of places to bond the exposed structural metal to is the service equipment enclosure, so if that's the service panel, the location is fine. Is that a lay-in lug sized for the conductor, mounted to a tapped hole in the enclosure and connected with a screw engaging at least 2 full threads? If so I would expect the connection to be OK.

I don't have a sense of scale, is the top breaker position no more than 80" above the floor?

Cheers, Wayne

 

[Joshua5438]

It is a lug sized for the 4awg wire. I actually used a self tapping screw. Is that acceptable?

Top breaker is actually 78" from finished floor.

 

[wwhitney]

Self-drilling/tapping is OK if it's, say, an 8-32 and the panel enclosure is 1/16" thick (which I'm pretty sure it has to be). A sheet metal screw is not.

You also have the option to remove some paint under the lug and bolt the lug to the enclosure.

Or you can move the bonding jumper to one of the terminal bars that is already connected to the enclosure, assuming it has a hole rated for the #4.

Cheers, Wayne

 

[Joshua5438]

Guess I will be changing the screw. I think the lugs are too small for a #4 wire. I will double check. Could I use the large lug on the end of the right neutral bar?

 

[wwhitney]

Sure, if it's rated for #4 (check the minimum size allowed). I assume there's a main bonding screw somewhere in that panel?

Cheers, Wayne

 

[Joshua5438]

Yes. It is in the top right neutral bar.

 

[Joshua5438]

This should work.

 

[wwhitney]

Looks like you used a pretapped hole intended for a grounding bar, and you found a machine screw that fits it? Sounds good.

Most ductseal I've seen is grey, is that some blue ductseal around the service conductors?

Cheers, Wayne

 

[Joshua5438]

You are correct. Figured that was the best way.

That is just painters tape to keep the lizards out until the meter is installed. Will remove before inspection. Wasn't sure if I could put anything inside it or not.

Any comments on the meter box I need to correct?

 

[wwhitney]

Yes, you are required to block the conduit passing from inside to outside to prevent air movement that could cause condensation. Duct Seal is the usual product used in the conduit, applied at one end or the other. It's like modeling clay.

The neutral conductor needs white tape in both enclosures. I assume conduit protecting the grounding electrode conductor is non-metallic? If it's metallic, it needs to be bonded to the GEC at each end of the conduit.

Oh, and of course all the lug connections need to be torqued with a torque wrench/screwdriver to the torque listed in the manufacturer's instructions, and you should have the tool on hand during the inspection.

Cheers, Wayne

 

[Joshua5438]

I will look for the duct seal.

Marking wire is easy enough. Already had that in mind.

The ground wire is in pvc so it should be good.

I torqued all the bolts to spec. I will keep my inchpound wrench close by during inspection.