I doubt it really makes that much difference. Concrete is really the
conductor. The NFPA determination was that 20' of rebar OR copper will
bond to the concrete footer. 250.52(A)(3)
On the other hand in a swimming pool they want a 12" x 12" grid to
bond that concrete. 680.26(C)
I think the truth may actually be somewhere in between.
I thought the main contribution of the concrete was leaching alkalinity
into the soil, increasing conductivity. I liked your idea, in another
thread, of tying the rebar all the way around the foundation.
Although thats for equipotential, not earthing.
Is there a deteriorating effect of concrete on bare copper grounding
conductor and parts like split bolts around the pool.
Was thinking of the deck, where I believe concrete interior is often
'damp'. And more particularly copper in "concrete encased electrode" by
itself. And connecting copper to rebar and floor mesh in concrete do you
get galvanic corrosion?
I thought corrosion was a reason for requiring a pool bonding wire to be
solid, not stranded (680.26-C). (Not arguing, just trying to put the
They do reqire a listed device to make thgis connection and most AHJs
want to see a bronze 2 part clamp so the copper and steel are not in
contact. Erico has an acorn listed for rebar but it is a "ground rod"
clamp used for Ufers, most say not for pools.
I agree, the "solid" is for better corrosion resistance and less
chance of physical damage. Personally I wish they would address the
damage issue more. It is not unusual to find the bonding conductors
broken on "old work".
BTW the #8 to the underwater light from the J box can be stranded but
it also has to be potted. This is really somewhat a redundant wire
since you also bond the niche to the pool steel with a #8 solid on the
concrete side but it is still required
There is no burial depth requirement so I imagine the yard man hits
them with an edger. Around the pool equipment they are usually just
laying on the ground. On my pool I put the ground wire under the pipes
going to the pump but that takes coordination between the plumber and
electrician. (both me in this case)
You have the opportunity to make the best electrode available. I
assume you are pouring a new concrete floor? If so, dig a small trench
around the perimeter, ring it with 1/2" rebar on chairs and use that
for your "Ufer" electrode. Don't put plastic under this part of the
pour so the concrete in the ring is in contact with the dirt If you
also tie that to the wire in the slab pour you have created a ground
plane under your basement.
There are two choices in coming up. You can stub up a piece of rebar
abnd connect to that (some AHJs will not accept this method) or bring
up a #4 copper that was connected to the rebar with a listed acorn or
other "rebar" rated connector. It is best to run a piece of RNC (grey
PVC) sleeve over this conductor, into the pour so it doesn't get
BTW if you do want to take your vapor barrier all the way to the wall,
lay it out on the floor part, roll it back around the edge and pour
your trench up to the base of the floor dirt level, flip the vapor
barrier over the wet concrete and pour the floor.
If you are going to pour a concrete slab with rebar, why just not ground
your electrical system to the rebar? Would that not provide a much better
ground than a couple of pieces of copper? Just wondering!
All the rebar should be inside the concrete. This is to prevent rusting
which would cause the rusted rebar to expand and crack the concrete. You
would have a very poor electrical ground if this is done.
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