#8 copper bonding wire in equipment pad: is stranded ok?

MitchRyan912

LifeTime Supporter
Jul 21, 2015
338
Madison, WI
I just realized I made an oversight and accidentally used stranded #8 copper wire instead of solid #8 to bond to the wire mesh in my concrete pad, a new pour last weekend. Is this a huge deal, or will it be OK so long as there is a #8 solid running to the pool frame, ladders, etc?
 

gwegan

TFP Expert
Apr 19, 2013
2,769
Sacramento, CA
Most Inspectors would fail you.

The code requires solid wire for several reasons. First sold wire has greater current carrying capacity as compared to the same size of stranded wire. Another way of saying that is that sold wire has less resistance than stranded wire. Why is that important? Well in a bonding system you want the bonding system to have as little resistance as possible so voltage is equal throughout the system. The standard calls for a #8 sold copper wire. That will have less resistance than a #8 stranded copper wire.

More importantly stranded copper wires, especially uninsulated wire, are susceptible to corrosion from the inside out. Uh?

In other words instead of having the outside of one copper wire corrode, we have many corroding because stranded wire has multiple times the surface area of solid wire. Corrosion further reduces the cross section of the wire and its ability to act as a low resistance bond connection.
 

MitchRyan912

LifeTime Supporter
Jul 21, 2015
338
Madison, WI
Any chance I lucked out by using TWO #8 stranded wires? If it's about current carrying capacity, then a pair of #8 stranded wires will have more capacity than a single #8 solid.

If not, how in the world can I fix this in 2 days without tearing up a brand new pad? PB will be here to set the gear on the pad on Monday!
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,998
Franklin, NC
Any chance I lucked out by using TWO #8 stranded wires? If it's about current carrying capacity, then a pair of #8 stranded wires will have more capacity than a single #8 solid.

If not, how in the world can I fix this in 2 days without tearing up a brand new pad? PB will be here to set the gear on the pad on Monday!
If you used stranded wire how did you attach it to the rebar? Plus, if you have already poured, how would add the second #8 stranded inside the concrete?

I'm sorry to say (as Gordon pointed out) that most inspectors will fail the inspection. The code is specific to solid wire.
 

MitchRyan912

LifeTime Supporter
Jul 21, 2015
338
Madison, WI
I put two #8 wires in before I poured, attaching them in two spots to the wire mesh (no rebar) with a pair of split bolt connectors. I sanded down the mesh to remove all the rust, to give it a better connection to the wire.
 

gwegan

TFP Expert
Apr 19, 2013
2,769
Sacramento, CA
So go invest in some more split bolts and where the two wires emerge from the slab connect solid #8.

I'm not going to tell you that complies nor will I tell you that will pass an inspection. To comply you have to jack the slab.

However I will say stranded encased in concrete will probably corrode less if exposed. You don't want bare stranded out exposed to the weather or buried in soil. Trippe no to buried in soil.
 

MitchRyan912

LifeTime Supporter
Jul 21, 2015
338
Madison, WI
Didn't you have to have the bonding inspection BEFORE the concrete was poured?
I built the pad myself, and didn't know that an inspection was needed. This project is considered a repair of an existing IG pool (built 40+ years ago). I'm not sure how that affects things, but had we used the old pad instead of putting the gear in this new location, then there would have been no bonding of ANY kind done on that old pad, much less any other part of the pool. The ladders were previously grounded with the ground conductor in a 12/2 romex, connected to the water spigot nearest to the pool. The steel wall frame of the pool was never bonded.
 

ccp4321

Active member
Mar 3, 2015
31
Texas
My equipment pad (built last year) has rebar in it but there was no bonding to the pool or the equipment located on it. The equipment is bonded using solid copper wire to the pool and decking around it though. It passed inspection. (Houston, Texas)
 

MitchRyan912

LifeTime Supporter
Jul 21, 2015
338
Madison, WI
So go invest in some more split bolts and where the two wires emerge from the slab connect solid #8.

I'm not going to tell you that complies nor will I tell you that will pass an inspection. To comply you have to jack the slab.

However I will say stranded encased in concrete will probably corrode less if exposed. You don't want bare stranded out exposed to the weather or buried in soil. Trippe no to buried in soil.
You can see in this picture of the concrete after pouring, the 60' length of wire sticking out of the side (corner closest to the bottom of the pic). That wire also comes out through the top of the concrete, so it exits the form in two spots.
IMG_4360.jpg
Might I be able to attach a solid #8 to that long length of stranded #8, and bury that connection in a small form of concrete to prevent it from being exposed to the elements? At that point, I'd just attach everything together from this new connection and cut off the wire sticking out of the concrete. Thoughts? Might I be any closer to passing, assuming there even is a bonding inspection on a rebuild project? (I question that there even will be a bonding inspection, as bonding never came up in talks with either the PB nor the PB's preferred electrician.)
 

CJadamec

TFP Expert
Apr 29, 2016
2,390
Quaker Hill, CT
So to make you life easier and because you technically didn't need to bond the pad because it is so far away from the pool. Get your solid lie and use a connector to that stranded wire in the slab. Then run the solid up onto the pad to go to your pump and heater. Then run it out to your pool and you will be fine.
 

MitchRyan912

LifeTime Supporter
Jul 21, 2015
338
Madison, WI
Pretty sure that's the best news I've heard all day! I went to bed in a bit of a panic last night, as my wife wasn't really thrilled with doing a concrete pad (she wanted 2'x2' pavers), so I never would have heard the end of it if I had messed up something... on the electrical end of the pad build!