portable spas and grounding grids

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electricguy61

electricguy61

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Remotely running business in Bay Area, CA from Med
Can someone explain to me the reasoning behind installing a grounding grid under a concrete slab installed for a portable spa (where by design there is no exposed metal)?

Also, where would you connect the bonding wire on the equipment? The lug on the pump motor? The grounding conductor bar? Couldn't doing so induce a fault current (if the bonding grid is a better ground source then the main grounding electrode)?

I've read the code numerous times (680), but it doesn't seem to make sense to apply it to portable spas. Many inspectors on the forum seem to think it does.

Thanks for the help.
 
Andy, sorry to bounce you to a new post that was not my intention. Is this portable spa outdoors? See 680.42 I assume it is, therefore it is covered by the permanant swimming pool rules. And the permanent swimming pool rules require the bonding grid.
 
I thought I did. If there is a lug on the motor bond it to the grid. If there is any other exposed metal then bond that to the grid also. If there is no exposed metal than do not worry about bonding non existing metal. Permanent swimming pools require a bonding grid, outdoor spa's require using the rules for permanent swimming pools, and thus you must have your bonding grid. Any other questions?
 
andycook said:
This must be a tough question. Lot's of readers, but no replies.
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You're darned right it is. :)

Come on guys! Some of you live for this kinda thing.
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What aspect? Arguing? Someone else has to go first. :D

I'm short on time, but I love discussing 680, in preparation for actually doing a project governed by it. Bare that in mind.

So, a quickie until I return to think deeper on it:
Couldn't doing so induce a fault current (if the bonding grid is a better ground source then the main grounding electrode)?
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It can't "induce a fault current." A fault current is current flowing the wrong way, or too much of it. As in, hot wire touching ground is a fault current.

Since the neutral is seperated from the EGC at the tub, then neutral current should not flow from the tub out through the earth.

So, let's pretend the slab is really, really good. Neutral current flows out to the service, and then looks at it's paths back to the source. There's a conductor at close to zero ohms, and an EGC (going into the house, towards the pool, etc) with a higher resistance.

99.9% of the neutral current is going to flow as we intended, out the service neutral conductor. .1% is going to flow into the grounding electrodes, taking that path. The tub's slab is a percentage of that .1%.

That should get ya started, I'm late. :)
 
andycook said:
Can someone explain to me the reasoning behind installing a grounding grid under a concrete slab installed for a portable spa (where by design there is no exposed metal)?

Also, where would you connect the bonding wire on the equipment? The lug on the pump motor? The grounding conductor bar? Couldn't doing so induce a fault current (if the bonding grid is a better ground source then the main grounding electrode)?

I've read the code numerous times (680), but it doesn't seem to make sense to apply it to portable spas. Many inspectors on the forum seem to think it does.

Thanks for the help.
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Equipotential grid now required in or under the permanently installed pool, outdoor spa, and outdoor hot tub deck to help mask stray voltage from utility wiring errors, deteriorating primary utility neutral conductors, ground faults that have not cleared, as well as appliance and equipment leakage current

1100723628_2.jpg
 
andycook said:
Can someone explain to me the reasoning behind installing a grounding grid under a concrete slab installed for a portable spa (where by design there is no exposed metal)?

Also, where would you connect the bonding wire on the equipment? The lug on the pump motor? The grounding conductor bar? Couldn't doing so induce a fault current (if the bonding grid is a better ground source then the main grounding electrode)?

I've read the code numerous times (680), but it doesn't seem to make sense to apply it to portable spas. Many inspectors on the forum seem to think it does.

Thanks for the help.
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Any time you are bonding you are connecting metals together... to make them one per say... Your confusing bonding with grounding.... You have to remember GROUNDING is for lightning protection, BONDING establishes an effective ground-fault current path for non-current carrying conductors..... help any? So with rebar in concreat BONDED to a pump motor, your creating a path for stray voltage back to it's source... without it, someone could get killed... the reason for doing this around pools, hot tubs and the like, I assume is the water factor...
 
Stick, in the case of equipotential bonding, it is to make the entire area at the same potential. Fault clearing ability is more of a side effect.

Check out this thread.

People immersed in water is the key; skin resistance drops a heap when immersed in water.
 
Please ignore that last post I made. It was something I should never have hit the reply key on and those were actually real right on explanations. I had me a rotten day and should have just come home and kicked the computer instead.
 
macmikeman said:
Please ignore that last post I made. It was something I should never have hit the reply key on and those were actually real right on explanations. I had me a rotten day and should have just come home and kicked the computer instead.
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Are you referring to the post where you said
The real reason is because the code says do it. The End.
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?

I tend to agree with you on your statement. There are a lot of things in the code that are not there for any discernible reason. But they are there, and they still have to be followed.
 
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