Spa bonding to grounding electrode

[bigwilleus]

I'm looking to add a concrete patio off the back of my house where my meter base is located. In doing this my #8 bare wire going to my ground rod will then be encased in rebar reinforced concrete. The patio slab will also extend over past my house and up to a retainer wall that is about 2' higher than the patio slab where there is another rebar reinforced slab for vehicle parking. On the patio slab I'm planning to put a hot tub that will be about 2' from the parking area retainer wall. Does this hot tub now need the equipotential bonding around it being it is with in the 30" to the parking area slab? The concrete slab for the parking isn't technically a metal object but it is definitely current carrying. If i put the equipotential bond for the hot tub, then it will be bonded to the grounding electrode via the rebar reinforced concrete patio slab. Any thoughts on this.

 

[tom baker]

Have you read over article 680 Part I and the part for hot tubs? Its very important to understand the #8 is not a grounding conductor but a bonding conductor.

 

[Dennis Alwon]

Yes,, I believe you need the equipotential bonding. It is fine if it is in contact with the grounding electrode conductor but it does not need to be connected to it. It wont hurt if there is incidental contact with the grounding electrode conductor.

 

[bigwilleus]

So I already have an existing ground rod for my service. Should I extend my existing ground wire, that is going to the ground rod, to connect to the rebar that will be in the future patio slab. The a piece of the rebar reinforcement is only a few inches away from the existing ground rod. Whether this connection is done or not my equipotential ring for the hot tub will be approximately 6’ away from the existing ground rod. If the ground wire is attached to the rebar reinforcement then this will basically make the hot tub part of the grounding electrode due to the rebar being tied together. Which I don’t think is the greatest idea. This is why I’m a bit stumped about what to do.

 

[bigwilleus]

Attached is a couple of sketches of what I'm referring to. As the saying goes a picture is worth a 1000 words. Hope this helps explain what I'm trying to say. So basically do I go ahead and attach the wire for the existing ground rod to the rebar in the future patio concrete slab. That is basically part 1 of 2. Now for part 2. I run my equipotential for the hot tub that will sit on the future slab. In doing this the equipotential bond (#8bare) will be steel tie wired to the rebar in the concrete. This is the same rebar that is now going to be part of the grounding electrode. So now I have my hot tub grounded instead of bonded. At this point stray voltage is going to be a concern coming up from into my grounding electrode which will then be on my bonded hot tub. Any recommendations on this.

 

[chrismarcellino]

Wont matter. The bonded parts and grid will be connected to the EGC which will be connected to the GEC anyhow via the grounding bus of the service disconnect via a low resistance connection. You are just making it even lower. I do not see any code violation as long as you clamp the rebar independently of the GEC components and use at least 8 AWG copper.

The purpose of equipotential bonding is to bring all of the surfaces, metal and water to the same potential, to minimize the risk of shock. That potential should will be very close to the GEC’s since there should be no current on the EGC from the hot tub.

If NEC 2014 or later, (or 2011 plus the accepted TIA,) you could also dispense with the equipotential bonding entirely by moving your listed and outdoor freestanding and above ground hot tub 30” away from any surfaces within 28” from the top of the tub (680.42(B)). If you can move it 6 more inches?

(Also, call your AHJ.)

 

[bigwilleus]

Thanks for the advice.