Installing Grounding rod

[glockman]

I have a question. I am building a 25'x40' detached garage. Got all the wiring inside done. When the foundation was poured I put a 4" pipe in the wall just above the footing. I ran 3" pvc conduit through that with a 90 then up to floor level, then two 33's put it in the wall and up to the panel. I never even thought about grounding rods. The conduit was ran to the house where I will tie into the service and has been barried. How is the best way to get wires from the grounding rods outside into the building? The building is framed and sided but the floor is still open (gravel) where my conduit comes up inside. Thanks in advance, this forum is awesome.

 

[MrMark]

The best way is to drill a 3/4" hole from the inside at an angle through the footing and drive the rod down so that only the top of the rod comes out inside your wall cavity. I would say 70 degrees is the right angle.

 

[glockman]

How far below the ground outside does the rod have to be. My floor grade is a bit higher than the ground outside. Thanks for the reply.

 

[mrb]

The best way is to drill a 3/4" hole from the inside at an angle through the footing and drive the rod down so that only the top of the rod comes out inside your wall cavity. I would say 70 degrees is the right angle.

you have to have 8 feet of rod in soil, so he would need a longer than normal rod to do this.

Utah is under 2008 NEC -dont you need a UFER ground?

dont forget you need 4 wires from your house to the subpanel -hot, hot, neutral, ground.

 

[MrMark]

Yes, you would get a 10 ft rod. If you have tough soil there is a cool attachment to a rotohammer that you can get to use the rotohammer to beat the rod down.

 

[glockman]

Not sure what a UFER ground is. I called the city today and they said two 5/8 rod 6 feet apart would fulfill code requirement( along with the ground coming from the panel in the house. I am running 4 #2 al from a 70 amp breaking in my main panel . So once i have the rod pounded through the footing, I will set the top of the rod about a foot below the finished floor grade. Run the wires up along the foundation wall and into the studs, then over into the panel correct? Does the wire need to be protected/insulated?

 

[MrMark]

No. The wire needs no protection unless you live in Newport Beach and then it will be hot.

 

[Aceman]

We'd most likely drive the rods in flush with the bottom of the slab. Then ziptie the ground wire up the backside of the conduit going to the panel where it's out of harms way. But if you can manage to hide it in the wall somehow without it being exposed at all, even better.

The easiest and best method is to tie onto the footing rebar before it's poured so you don't even need to drive rods. But it seems everyone asks about grounding AFTER they throw up the building. Here in Oregon, there's a good possibility you be chipping concrete to access the rebar because it's required to be used.

 

[Norcal]

No. The wire needs no protection unless you live in Newport Beach and then it will be hot.

See 250.64 (B) 2008 NEC

(B) Securing and Protection Against Physical Damage.
Where exposed, a grounding electrode conductor or its enclosure
shall be securely fastened to the surface on which it
is carried. A 4 AWG or larger copper or aluminum grounding
electrode conductor shall be protected where exposed to
physical damage. A 6 AWG grounding electrode conductor
that is free from exposure to physical damage shall be permitted
to be run along the surface of the building construction
without metal covering or protection where it is securely
fastened to the construction; otherwise, it shall be in
rigid metal conduit, intermediate metal conduit, rigid nonmetallic
conduit, electrical metallic tubing, or cable armor.
Grounding electrode conductors smaller than 6 AWG shall be
in rigid metal conduit, intermediate metal conduit, rigid nonmetallic
conduit, electrical metallic tubing, or cable armor.

 

[mrb]

isnt there something too, where unless the clamp is non reversable (cadweld) it has to be accessable?

 

[98xjroks]

I'm in Central UT and mine was just inspected, i'd say it's about 5 feet long. Mine was tied into the rebar footing and poured into the foundation if that make a difference.

I could confirm this, but I'm thinking that all I have coming out of my "b" sub-panel from my house to my garage is three wire.

 

[glockman]

We'd most likely drive the rods in flush with the bottom of the slab. Then ziptie the ground wire up the backside of the conduit going to the panel where it's out of harms way. But if you can manage to hide it in the wall somehow without it being exposed at all, even better.

The easiest and best method is to tie onto the footing rebar before it's poured so you don't even need to drive rods. But it seems everyone asks about grounding AFTER they throw up the building. Here in Oregon, there's a good possibility you be chipping concrete to access the rebar because it's required to be used.

I like the idea of tying it to the backside of the conduit. Looks better and is more protected. I will contact the city tomorrow and verify that this is OK. The inspector I talked to today was less than knowledgable. As for remembering after the fact, this is the only thing I totally spaced off up to this point. Not to bad for a first timer. The only part I contracted was the footingsfoundation since forms, renting or buying plywood was more than they charged me to pour them. Thanks again for the advice. I wish I had found this site in 08.

 

[Norcal]

isnt there something too, where unless the clamp is non reversable (cadweld) it has to be accessable?

That is one of the exceptions.

250.68(A) 2008 NEC

(A) Accessibility. All mechanical elements used to terminate
a grounding electrode conductor or bonding jumper to
a grounding electrode shall be accessible.
Exception No. 1: An encased or buried connection to a
concrete-encased, driven, or buried grounding electrode
shall not be required to be accessible.
Exception No. 2: Exothermic or irreversible compression
connections used at terminations, together with the mechanical
means used to attach such terminations to fireproofed
structural metal whether or not the mechanical
means is reversible, shall not be required to be accessible.

 

[dougmac]

I am not a certified electrician. I just drilled a hole in the siding and ran the conductor through it down to the rods. Mine passed inspection....

Feel free to point out anything that you don't like about it if it would help the OP.....

 

[IDASHO]

It certainly doesnt have to be fancy.

I did mine similar.

Only real difference is that I thought ahead, and buried the ground rod in the service entrance ditch.

 

[walrus]

Here in Oregon, there's a good possibility you be chipping concrete to access the rebar because it's required to be used.

From what I understand you definitely will in Massachusetts, they make no exceptions, you got rebar it will be used. In Maine they using them when available but I doubt jackhammering is being used if you didn't. Maybe in a couple of cities where there are city inspections

 

[Falcon67]

I just wonder about the UFER thing - not questioning code, but I wonder if it's as reliable as thought. Seems to me that double copper rods 8' in the ground with brass clamps retaining copper wire is quite a bit more reliable than rusty rebar held together with twist ties that may have a few pieces stuck a little bit in the ground. Concrete doesn't strike me as being all that conductive. I'm betting that on a garage slab around here that there aren't very many sticks of rebar in the ground, an none over a foot deep. Last rain we had was not even an inch at the beginning of October, how conductive do you think the ground is about 12" down. I can see the advantage in places where footers are in the dirt and may expose a lot of iron bar to the soil, but around here footers don't see a lot of digging on single story buildings. And you know they don't put any more steel in there than they can get away with. I suppose that if the resistance is where it needs to be, what works - works. UFER just looks more like a ground plane in a circuit board, and would seem to be better with copper rods driven at 4 building corners and the steel tied to the ground rods. That should provide a low resistance path from any piece of steel to the earth.

 

[mobetta]

AFAIK if your rebar is contacting soil it is in violation of code.

 

[nate379]

I just put my ground wire in the conduit. Drilled a hole in the side of the conduit a little below ground level and pulled it through to connect.

I just ran conduit on the verticals, wire was UF so I laid that in trench without anything, just put good sandy soil with no rocks around it.

My trench was 3-4ft deep though. Was told "code" here (hardly enforced) says 36" for power lines, but only 18" for gas lines

 

[larry_g]

I am not a certified electrician. I just drilled a hole in the siding and ran the conductor through it down to the rods. Mine passed inspection....

Feel free to point out anything that you don't like about it if it would help the OP.....

This looks like what I did for mine, marion county oregon, in 2008. I asked the county inspector about the ufer ground and was informed that either a preinspected ufer OR ground rods. This was an inspected install.

lg
no neat sig line

 

[mrb]

code (2008) says if you have a footing with rebar in it you HAVE to bond it -not optional

 

[Falcon67]

Googleing UFER would have saved me the trouble of posting LOL. Turns out that concrete is a decent conductor.

 

[Norcal]

Googleing UFER would have saved me the trouble of posting LOL. Turns out that concrete is a decent conductor.

A Ufer (CEE, concrete encased electrode) is way better then a ground rod.

 

[acer66]

A Ufer (CEE, concrete encased electrode) is way better then a ground rod.

Might be a very stupid question but could you "over insulate" the concrete slap so that the grounding function might be compromised or is the slap itself the ground?

Thank you

 

[IDASHO]

Dunno the reason, but when I built my garage, the inspector requested a UFER and a ground rod.

I had already had the UFER in the plans, and the ground rod was an easy thing to do, so I did both.

UFER

Ground rod

 

[walrus]

Might be a very stupid question but could you "over insulate" the concrete slap so that the grounding function might be compromised or is the slap itself the ground?

Thank you

If you have a footer buried under the slab, thats where you want your rebar(UFER) to come from. If you have a slab on grade and you have 2" of styrofoam under it I see no reason to hook to that as its insulated from the earth, you'd have to drive ground rods

 

[Norcal]

Here is the code art. from the 2008 NEC 250.52 (A)3



3) Concrete-Encased Electrode. An electrode encased
by at least 50 mm (2 in.) of concrete, located horizontally
near the bottom or vertically, and within that portion of a
concrete foundation or footing that is in direct contact with
the earth, consisting of at least 6.0 m (20 ft) of one or more
bare or zinc galvanized or other electrically conductive
coated steel reinforcing bars or rods of not less than 13 mm
(1⁄2 in.) in diameter, or consisting of at least 6.0 m (20 ft) of
bare copper conductor not smaller than 4 AWG. Reinforcing
bars shall be permitted to be bonded together by the
usual steel tie wires or other effective means. Where multiple
concrete-encased electrodes are present at a building
or structure, it shall be permissible to bond only one into
the grounding electrode system.