Cement Pad And Electrical Questions

[TimRob]

First time poster and soon to be first hot tub! I have a a few questions that hopefully somebody can answer.

I'll have my new Relay hot tub, 7'x7', delivered as soon as the ground drys up.

I wanted to do a cement pad as I live in Michigan. I do not want to worry about heaving. I know the ground heaves, as my old deck heaved up at least 6" over the years.

One side of the tub will but up against the deck. I may extend the deck steps to a second side. The other 2 sides will remain open.

I wanted to do the cement work myself to save some money. I'll start by excavating the topsoil. How much base gravel and or sand should I use for a 4" cement pad?

For the electrical, the city inspector said I need a metal mesh throughout the cement pad and 3 feet surrounding the tub. The mesh will be grounded to the hottub wiring. He gave me a copy of the National Electric Code. I can see clearly where the mesh is needed for pools, but in the hot tub section, it doesn't say anything about the metal mesh. Does anybody have experience if the mesh is needed?

Thanks for your help in advance.

[SHOWEM]

Thats because it is not required! The mesh is to reinforce the cement pad. Mesh in a permanent inground pool reinforces the pool but also is a PART of the pool that is why it needs to be bonded/grounding. With all due respect the inspector is WRONG. Is he new on the job? The hot tub is also PORTABLE NOT PERMANENT. Permanent has different requirements than a portable installation. This is the inspectors way of saying: I DON'T WANT YOU DOING THE WORK HIRE PROFESSIONALS!. Just my opinion, good luck.

[hot_water]

Thats because it is not required! The mesh is to reinforce the cement pad. Mesh in a permanent inground pool reinforces the pool but also is a PART of the pool that is why it needs to be bonded/grounding. With all due respect the inspector is WRONG. Is he new on the job? The hot tub is also PORTABLE NOT PERMANENT. Permanent has different requirements than a portable installation. This is the inspectors way of saying: I DON'T WANT YOU DOING THE WORK HIRE PROFESSIONALS!. Just my opinion, good luck.

Current NEC does require bonded mesh (bonded rebar ties together is ok) for portable spa/hottub installations. Many if not most jurisdictions are ignoring the requirement, but some are holding homeowners to it. You should heed your local inspector. The requirement addresses potential stray voltage hazard, which is very rare but there are cases.

Because the requirement is considered onerous and the hazard is uncommon, NFPA (owners of the NEC) are currently considering an amendment that will remove the requirement for portable spas. The bonding requirement really affects people that are installing or replacing spas on existing slabs that don't have the mesh or rebar in place. I don't know if the requirement has been relaxed yet. In any case, final authority always lives with the local building department. Even if NEC removes the requirement, your local jurisdiction may not or may take a long time to do it.

You can put wood (such as decking) on the slab under the spa and out to the 3' perimeter requirement to get around the requirement, but that can add $$.

Since you're pouring the slab, it shouldn't be much of a problem put in the mesh and bond it or just use the rebar. Unless your inspector is a jerk, he'll probably tell you what your building department will approve if you ask him.

[TimRob]

Thanks for the info. A few more questions.

To bond the mesh to the wiring, is a ground clamp such as one of these links below suitable? I'll be bonding the mesh together as the pieces aren't big enough, and bonding the mesh to the wiring.

http://www.grainger.com/Grainger/ERITECH-Ground-Rod-Clamp-2KXN2?Pid=search

bronze

http://www.homedepot.com/h_d1/N-5yc1v/R-100353838/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

bronze

http://www.homedepot.com/h_d1/N-5yc1v/R-100198848/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

bronze

I talked to my Dad, a retired electrician. He said we could bond the steel mesh together steel wire. We'll use the clamp for bonding the mesh to the the wiring.

Does the conduit have to be rigid? Is thin wall ok?

Edited May 10, 2011 by TimRob

[hot_water]

Thanks for the info. A few more questions.

To bond the mesh to the wiring, is a ground clamp such as one of these links below suitable? I'll be bonding the mesh together as the pieces aren't big enough, and bonding the mesh to the wiring.

http://www.grainger.com/Grainger/ERITECH-Ground-Rod-Clamp-2KXN2?Pid=search

bronze

http://www.homedepot.com/h_d1/N-5yc1v/R-100353838/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

bronze

http://www.homedepot.com/h_d1/N-5yc1v/R-100198848/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

bronze

I talked to my Dad, a retired electrician. He said we could bond the steel mesh together steel wire. We'll use the clamp for bonding the mesh to the the wiring.

Does the conduit have to be rigid? Is thin wall ok?

I would ask the inspector about the bonding fitting and the conduit. I've used the first two clamps you referenced for ground rods, and the last for bonding to a pipe, but not sure if or how well these types will work for mesh. Doesn't seem like they will close down enough. In my area, they are not requiring the bonding.

Here they allow any approved conduit as long as it's correctly installed (for instance, burial depth varies). But what the building department allows in anyone else's area doesn't have a lot to do with what your inspector wants to see. Your dad should know what will work, as the pool requirement isn't new.

[TimRob]

I confirmed a split bolt is used to bond the mesh together. It's also used to bond the #8 wire to the mesh. The #8 wire would then be bonded to the hot tub wiring/bar.

Tthe inspector gave me a chart for the different types of conduit. EMT is not acceptable. He said I could use PVC, and bury it 18". 6" if under cement.

[hot_water]

I confirmed a split bolt is used to bond the mesh together. It's also used to bond the #8 wire to the mesh. The #8 wire would then be bonded to the hot tub wiring/bar.

Tthe inspector gave me a chart for the different types of conduit. EMT is not acceptable. He said I could use PVC, and bury it 18". 6" if under cement.

Sounds like you're good to go. I used pvc, but here we have to go 24" down. If I had to do it again, I would probably go with ridgid, which costs more but requires so much less digging.

[SHOWEM]

Thats because it is not required! The mesh is to reinforce the cement pad. Mesh in a permanent inground pool reinforces the pool but also is a PART of the pool that is why it needs to be bonded/grounding. With all due respect the inspector is WRONG. Is he new on the job? The hot tub is also PORTABLE NOT PERMANENT. Permanent has different requirements than a portable installation. This is the inspectors way of saying: I DON'T WANT YOU DOING THE WORK HIRE PROFESSIONALS!. Just my opinion, good luck.

Current NEC does require bonded mesh (bonded rebar ties together is ok) for portable spa/hottub installations. Many if not most jurisdictions are ignoring the requirement, but some are holding homeowners to it. You should heed your local inspector. The requirement addresses potential stray voltage hazard, which is very rare but there are cases.

Because the requirement is considered onerous and the hazard is uncommon, NFPA (owners of the NEC) are currently considering an amendment that will remove the requirement for portable spas. The bonding requirement really affects people that are installing or replacing spas on existing slabs that don't have the mesh or rebar in place. I don't know if the requirement has been relaxed yet. In any case, final authority always lives with the local building department. Even if NEC removes the requirement, your local jurisdiction may not or may take a long time to do it.

You can put wood (such as decking) on the slab under the spa and out to the 3' perimeter requirement to get around the requirement, but that can add $$.

Since you're pouring the slab, it shouldn't be much of a problem put in the mesh and bond it or just use the rebar. Unless your inspector is a jerk, he'll probably tell you what your building department will approve if you ask him.

Just for future reference what article in the NEC states bonding rebar/mesh in pads for portable tubs/pools? Thanks in advance

[hot_water]

Thats because it is not required! The mesh is to reinforce the cement pad. Mesh in a permanent inground pool reinforces the pool but also is a PART of the pool that is why it needs to be bonded/grounding. With all due respect the inspector is WRONG. Is he new on the job? The hot tub is also PORTABLE NOT PERMANENT. Permanent has different requirements than a portable installation. This is the inspectors way of saying: I DON'T WANT YOU DOING THE WORK HIRE PROFESSIONALS!. Just my opinion, good luck.

Current NEC does require bonded mesh (bonded rebar ties together is ok) for portable spa/hottub installations. Many if not most jurisdictions are ignoring the requirement, but some are holding homeowners to it. You should heed your local inspector. The requirement addresses potential stray voltage hazard, which is very rare but there are cases.

Because the requirement is considered onerous and the hazard is uncommon, NFPA (owners of the NEC) are currently considering an amendment that will remove the requirement for portable spas. The bonding requirement really affects people that are installing or replacing spas on existing slabs that don't have the mesh or rebar in place. I don't know if the requirement has been relaxed yet. In any case, final authority always lives with the local building department. Even if NEC removes the requirement, your local jurisdiction may not or may take a long time to do it.

You can put wood (such as decking) on the slab under the spa and out to the 3' perimeter requirement to get around the requirement, but that can add $$.

Since you're pouring the slab, it shouldn't be much of a problem put in the mesh and bond it or just use the rebar. Unless your inspector is a jerk, he'll probably tell you what your building department will approve if you ask him.

Just for future reference what article in the NEC states bonding rebar/mesh in pads for portable tubs/pools? Thanks in advance

In NEC 2008, the relevant sections are 680.26 and 680.42. The requirement applies to spas we typically refer to as "portable", because they are not "cord and plug" and/or typically drained after each use.

Here is a link to the amendment that changes the (nutty) equipotential grid requirement. I don't know the approval status, however even if approved that doesn't mean that local authorities are obligated to honor the change. You always have to do what the local inspector says.

http://www.nfpa.org/Assets/files/AboutTheCodes/70/ProposedTIA1005NFPA70.pdf

[SHOWEM]

Thats because it is not required! The mesh is to reinforce the cement pad. Mesh in a permanent inground pool reinforces the pool but also is a PART of the pool that is why it needs to be bonded/grounding. With all due respect the inspector is WRONG. Is he new on the job? The hot tub is also PORTABLE NOT PERMANENT. Permanent has different requirements than a portable installation. This is the inspectors way of saying: I DON'T WANT YOU DOING THE WORK HIRE PROFESSIONALS!. Just my opinion, good luck.

Current NEC does require bonded mesh (bonded rebar ties together is ok) for portable spa/hottub installations. Many if not most jurisdictions are ignoring the requirement, but some are holding homeowners to it. You should heed your local inspector. The requirement addresses potential stray voltage hazard, which is very rare but there are cases.

Because the requirement is considered onerous and the hazard is uncommon, NFPA (owners of the NEC) are currently considering an amendment that will remove the requirement for portable spas. The bonding requirement really affects people that are installing or replacing spas on existing slabs that don't have the mesh or rebar in place. I don't know if the requirement has been relaxed yet. In any case, final authority always lives with the local building department. Even if NEC removes the requirement, your local jurisdiction may not or may take a long time to do it.

You can put wood (such as decking) on the slab under the spa and out to the 3' perimeter requirement to get around the requirement, but that can add $$.

Since you're pouring the slab, it shouldn't be much of a problem put in the mesh and bond it or just use the rebar. Unless your inspector is a jerk, he'll probably tell you what your building department will approve if you ask him.

Just for future reference what article in the NEC states bonding rebar/mesh in pads for portable tubs/pools? Thanks in advance

In NEC 2008, the relevant sections are 680.26 and 680.42. The requirement applies to spas we typically refer to as "portable", because they are not "cord and plug" and/or typically drained after each use.

Here is a link to the amendment that changes the (nutty) equipotential grid requirement. I don't know the approval status, however even if approved that doesn't mean that local authorities are obligated to honor the change. You always have to do what the local inspector says.

http://www.nfpa.org/Assets/files/AboutTheCodes/70/ProposedTIA1005NFPA70.pdf

Your going by the 2008 edition. How about the 2011 edition? With all due respect you are misleading people about: "you do what the local inspector says" Are you a license electrician? You can go in front of the state board and file a complaint against the local inspector if you feel you are right. One more issue, I don't think you had the right to line through my statement I made in a previous post. Let people use there own judgement. One more point,the GFI is there for a reason! Have a nice day!

[hot_water]

Thats because it is not required! The mesh is to reinforce the cement pad. Mesh in a permanent inground pool reinforces the pool but also is a PART of the pool that is why it needs to be bonded/grounding. With all due respect the inspector is WRONG. Is he new on the job? The hot tub is also PORTABLE NOT PERMANENT. Permanent has different requirements than a portable installation. This is the inspectors way of saying: I DON'T WANT YOU DOING THE WORK HIRE PROFESSIONALS!. Just my opinion, good luck.

Current NEC does require bonded mesh (bonded rebar ties together is ok) for portable spa/hottub installations. Many if not most jurisdictions are ignoring the requirement, but some are holding homeowners to it. You should heed your local inspector. The requirement addresses potential stray voltage hazard, which is very rare but there are cases.

Because the requirement is considered onerous and the hazard is uncommon, NFPA (owners of the NEC) are currently considering an amendment that will remove the requirement for portable spas. The bonding requirement really affects people that are installing or replacing spas on existing slabs that don't have the mesh or rebar in place. I don't know if the requirement has been relaxed yet. In any case, final authority always lives with the local building department. Even if NEC removes the requirement, your local jurisdiction may not or may take a long time to do it.

You can put wood (such as decking) on the slab under the spa and out to the 3' perimeter requirement to get around the requirement, but that can add $$.

Since you're pouring the slab, it shouldn't be much of a problem put in the mesh and bond it or just use the rebar. Unless your inspector is a jerk, he'll probably tell you what your building department will approve if you ask him.

Just for future reference what article in the NEC states bonding rebar/mesh in pads for portable tubs/pools? Thanks in advance

In NEC 2008, the relevant sections are 680.26 and 680.42. The requirement applies to spas we typically refer to as "portable", because they are not "cord and plug" and/or typically drained after each use.

Here is a link to the amendment that changes the (nutty) equipotential grid requirement. I don't know the approval status, however even if approved that doesn't mean that local authorities are obligated to honor the change. You always have to do what the local inspector says.

http://www.nfpa.org/Assets/files/AboutTheCodes/70/ProposedTIA1005NFPA70.pdf

Your going by the 2008 edition. How about the 2011 edition? With all due respect you are misleading people about: "you do what the local inspector says" Are you a license electrician? You can go in front of the state board and file a complaint against the local inspector if you feel you are right. One more issue, I don't think you had the right to line through my statement I made in a previous post. Let people use there own judgement. One more point,the GFI is there for a reason! Have a nice day!

Whoa - *I* did not line through your comments. Forum posters do not have the ability to do that. It was probably a moderator that did it, and I'm guessing that he/she did it because the Forum doesn't want to be responsible for incorrect advice in a safety area.

I cited 2008 because that is what most local building departments are still using. But the requirement for an equipotential grounding grid exists in 2011, in the same section. The amendment I provided a link to seeks to relax the requirement.

I don't think I'm misleading anyone. First of all, the NEC is not binding on any local jurisdiction. They are free to adopt all or it, part or it or use their own code. Yes, you *can* complain about an inspector, but you aren't going to have success unless he's interpreting or enforcing the *local* code incorrectly. In this case, since the requirement for a bonded equipotential grid has existed in NEC since 2005, it's likely that he's simply telling the homeowner what that jurisdiction requires.

With all respect, I believe your post is misleading. You assertively state that the local inspector is wrong, but your claim has no basis in the NEC or in the poster's local codes. Your logic regarding "portable" spas v. pools is simply incorrect. The equipotential grid requirement is aimed at mitigating stray voltage hazard, a relatively rare but real hazard. Personally I think the grid requirement is a burdensome, onerous and unnecessary one in light of the relative rarity of the hazard, but the fact is that if a local jurisdiction has adopted it, then *it is law*. Had you read NEC and understood it properly, and researched the issue of stray voltage, you would be familiar with the requirement, its application and the debate over this - and hopefully would not have made your post that the inspector was "wrong" or "new on the job". Had the original poster subscribed to your opinion, at best he would have risked alienating the inspector (never a smart move)and not getting his installation signed off. At worst, his jurisdiction may be enforcing the requirement because they have some history of stray voltages (which can be caused by a number of conditions) in that area and thus your opinion *may* be ignoring a real safety issue.

Regarding GFIs, they work by detecting imbalance in current of 5 milliamps or more between the two legs of the AC line. The presumption is that if the currents are not substantially equal, then current is going somewhere else - possibly through a person, but in any case not a good situation. Now, the equipotential grid is aimed at protection from another type of hazard - stray voltages that may exist in the ground. Since the water in a spa is electrically bonded to the equipment ground (green wire), without the grid, a potential difference between the green wire and stray voltage present in the ground can result in a shock when a person standing on the concrete pad touches the water. This is why the requirement extends around the periphery of the spa for 3 feet. It would be hard to touch the water from further than three feet away. While standing on the grid which is bonded to the green wire, your feet are at "green wire" potential and the water is also at "green wire" potential. Thus, there is no shock hazard. This type of fault would not result in an imbalance between the two legs of the AC line (whether the legs form the 240V line or one leg and the neutral for a 120V line), and thus the GFI *would not trip*. So, contrary to your assertion, the GFI offers no protection for the type of fault that the equipotential grid is intended to address.

Finally, no, I am not an electrician. I am an engineer. I personally would not think it wise to advise someone that an electrical inspector was wrong unless I was quite confident in my understanding of the issue. In this case, I default to the idea that inspector was probably right on the mark in terms of enforcing his local requirements. It may be an unnecessary requirement, but it is enumerated in NEC (until such time as the amendment is adopted by the individual jurisdictions). And, finally, a GFI is an ineffective protective measure for this type of hazard.

[TimRob]

I confirmed a split bolt is used to bond the mesh together. It's also used to bond the #8 wire to the mesh. The #8 wire would then be bonded to the hot tub wiring/bar.

Tthe inspector gave me a chart for the different types of conduit. EMT is not acceptable. He said I could use PVC, and bury it 18". 6" if under cement.

Sounds like you're good to go. I used pvc, but here we have to go 24" down. If I had to do it again, I would probably go with ridgid, which costs more but requires so much less digging.

I'm using pvc, which is stiff, not flexible. Is this not the same as rigid? What exactly is rigid? I like the idea of rigid for a few more bucks and a lot less digging. My run is only about 8', so cost difference will be minimal.

[TimRob]

I work in Automotive and am part of SAE, Soceity of Autmotive Engineers, taskforces. We write requirements such as the NEC. We will discuss a single sentence and how it can be interpretted for 30 minutes. I understand the pain when it comes to reading the NEC and similar documents.

[hot_water]

I confirmed a split bolt is used to bond the mesh together. It's also used to bond the #8 wire to the mesh. The #8 wire would then be bonded to the hot tub wiring/bar.

Tthe inspector gave me a chart for the different types of conduit. EMT is not acceptable. He said I could use PVC, and bury it 18". 6" if under cement.

Sounds like you're good to go. I used pvc, but here we have to go 24" down. If I had to do it again, I would probably go with ridgid, which costs more but requires so much less digging.

I'm using pvc, which is stiff, not flexible. Is this not the same as rigid? What exactly is rigid? I like the idea of rigid for a few more bucks and a lot less digging. My run is only about 8', so cost difference will be minimal.

You most likely have grey pvc conduit, probably common schedule 40. It will be marked on the conduit. You have to dig deep with pvc, even the heavier schedule 80. "Ridgid" is heavy steel conduit with threaded ends. Because it's steel, it is far less likely that someone will puncture it (and thus the wire, creating an eletrocution hazard) with a shovel or who-knows-what in comparison to pvc. So, most areas will let you bury it much shallower than pvc. It, and the fittings, are quite a lot more expensive than pvc -- but with only 8 feet of run I would go for the ridgid...unless you have a teenage son that you can bully into digging that trench, that is.

EDIT: Keep in mind that, just like the old days of galvanized water pipe, you may get away with stock lengths but depending on your situation you may have to be able to cut and thread ridgid conduit (or have it done to your measurements). Sorry I forgot to mention that... I sometimes assume that everyone has all the toys that I have accumulated over the years.