Hot Tub sitting on Pavers!

[davedottcom]

Ok, this sounds like a really bad idea to me but this is what a home owner (Acting as GC) wants to do...

7 man Hot Tub (5,200 lbs.) sitting on concrete pavers outdoors.

I haven't seen the prints for the pavers or footers yet. Oh yea, they are pouring footers so the perimeter of the pavers will also support & hold down a screen enclosure!

Ok, my question is... Will an Equipotential Bonding grid be required per 2005 680.26(C)?
Are pavers considered paved walking surfaces?!?

Dave

 

[dillon3c]

Re: Hot Tub sitting on Pavers!

IMO..I think it would dave.

680.26(b)(1)

 

[jimwalker]

Re: Hot Tub sitting on Pavers!

i see it no diferant than a concrete slap with no steel in it as for the paver part.But the footer will likely have rebar.Would think it good idea to bond to the ground system but no need for a rod.

 

[jwelectric]

Re: Hot Tub sitting on Pavers!

I haven't seen the prints for the pavers or footers yet. Oh yea, they are pouring footers so the perimeter of the pavers will also support & hold down a screen enclosure!

If this screen is metal and with-in five feet it will need to be bonded with a #8 to the bonding grid that is required to be installed under the pavers.

I love 680.26 (C)

 

[davedottcom]

Re: Hot Tub sitting on Pavers!

If this screen is metal and with-in five feet it will need to be bonded with a #8 to the bonding grid that is required to be installed under the pavers.

Yes, the Aluminum enclosure is exactly 5' away!
I already figured on bonding that.

Ok, I agree the pavers would be considered paved walking surface, and probably have the same conductive properties as poured concrete.

So, I'll be building my first Equipotential Bonding grid!

[ September 10, 2005, 10:12 AM: Message edited by: davedottcom ]

 

[jim sutton]

Re: Hot Tub sitting on Pavers!

680.26(C)(3)(a) requires the grid to be bonded at all points of crossing by a method in accordance with 250.8. Do they make a listed pressure connector for a no. 8 T connection?

By the way, the last pool I did (I dont do many), you cannot depend on the guys installing the structural reinforcing steel to tie the wires tight as required. They may not tie them at all!

It seems to me you would be better to make your own grid?

 

[normbac]

Re: Hot Tub sitting on Pavers!

it sounds like you are refering to a portable spa. If so the egc from the disconnect to the spa panel would do the job. As far as the screen goes it needs to be grounded unless you move it a few inches beyond 5 foot from the spa

 

[iwire]

Re: Hot Tub sitting on Pavers!

Originally posted by davedottcom:
I just skimmed over 680.26 (C) and it looks like #8 solid is exceptable. If I use one continuos piece of #8 I don't see the need for any connections within the grids.
Right?

Editted: I'm thinking of using tie wire just to hold the #8 into nice 12" grids but not for "connection" purposes. Connecting a wire to itself would be silly.... just silly...right?!

No it's not silly it must be done, its all about keeping everything at the same potential.

 

[dillon3c]

Re: Hot Tub sitting on Pavers!

I'm thinking of using tie wire just to hold the #8 into nice 12" grids but not for "connection" purposes. Connecting a wire to itself would be silly.... just silly...right?!

Dave,
In back tracking over my posting and the
reasoning of me pointing to 680.26(b)(1),
*or other conductive material is not available,provisions shall be made for an *alternative means to eliminate voltage gradients*

Taking you to 680.26(c)(3) *Alternative Means

I too Dave as of yet, have also never built this Equipotenial Bonding Grid mat,for the Pool or Spa.

680.26(d)refers you to 250.8

250.8 *by exothermic welding,listed pressure connectors,listed clamps,or other listed means.

I had seen in one of these classes attended,where Instructor showed pictures of the grid construction.It was of the constuction and connection of the overlaping wire in the squares,with a certain listed clamps in the pictures.

*I'm thinking it was JW's class, seeing how he really likes the subject of Article 680. But I can't really be sure @ this time, of the class/instructor.

This clamp shown,in picture @ class was sort-of "X" configuration,bolting in center of clamp,as I remeber in the photo reference.

Also,@ time of this class,in my understanding no one mass- manufactured this grid,as a pre-made assembly to sizes.(it had to be field constructed)

*I do know,it was one of these classes attended,because I have no complete illustration as I have explained in pictorial, in any of my text @ home.

Hope this helps you Dave.I'm sure someone will expand on this issue..

[ September 10, 2005, 02:42 PM: Message edited by: dillon3c ]

 

[dillon3c]

Re: Hot Tub sitting on Pavers!



[ September 10, 2005, 02:30 PM: Message edited by: dillon3c ]

 

[davedottcom]

Re: Hot Tub sitting on Pavers!

No it's not silly it must be done, its all about keeping everything at the same potential.

Now hold on a second! I think that rule is meant to bond two seperate pieces together, not the same piece to itself just because it passes over itself.

In other words two different pieces of rebar or #8 crossing over in a grid pattern would need to be bonded so they would be the same potential... but why would it be necessary to bond an unbroken #8 wire to itself?!?
Running an unbroken #8 in a 12" zig-zag pattern both ways to create a 12" grid would create 144 cross overs!

 

[infinity]

Re: Hot Tub sitting on Pavers!

Maybe something like this?


There are more photos here:

http://electrical-contractor.net/ubb/Forum2/HTML/002086.html

 

[iwire]

Re: Hot Tub sitting on Pavers!

Originally posted by davedottcom:
[Bob, are you saying it is possible for one unbroken #8 to have 2 different potentials? If so, please explain!

Yes it is possible and the reason is that the wire has resistance.

Hey you say, how much difference can there be?

I don't know, I can not imagine that it would be much.

That aside the rule is pretty clear.

They want you to bond each and every cross no mention if the grid is one continuous wire or made up of a 200 individual 14" pieces of wire.

I agree someone should make a roll down mat out of 8 solid CU, there must be somebody working on that.

If you did make this mat you could get good money for it as the labor for making up your own has got to be high.

 

[iwire]

Re: Hot Tub sitting on Pavers!

Looks like someone is making the grid.

About $700 for 160' x 2' roll.

 

[dillon3c]

Re: Hot Tub sitting on Pavers!

Thanxs for the pictures Infinity,

I didn't know a manufacturer pre-made this grid.At time of my class,I heard no..

Picture worth thousand words..

 

[jim sutton]

Re: Hot Tub sitting on Pavers!

How about installing your own structural reinforcing steel? The kind that is about 1/8" or 3/16" thick. The steel is already welded together at the cross points.

 

[pierre]

Re: Hot Tub sitting on Pavers!

There are several manufacturers that make the mats, I think Erico, Harger and others.



Grounding Grids, Mats & Assemblies


ERICO prefabricated wire mesh mats are convenient, efficient and economical for safe grounding in high voltage installations and wherever large area equipotential grounds are required.

Features
Manufactured from copper-clad wire, which combines the strength of steel with excellent conductivity and high corrosion resistance of copper surface coating
Both metals are molecularly bonded to each other
All of the intersections of the crossing wires are silver brazed with high temperature braze filler which means:
very high strength tolerance during installation and durability in the ground
outstanding electrical conductivity
corrosion resistant
temperature rating greater than 450? Celsius - limit for silver brazed connections (IEEE Std 80 1986)

Applications
Meshes of different dimensions can be buried as ground grids and safety mats in high and medium-voltage utility applications:
Wire sizes from 3 mm2 to 21mm2 (AWG #12 to #4)
Mesh sizes 51 mm x 51 mm (2" x 2") up to 1219 mm x 610 mm (4? x 2?)
High surface area of technically useable ground contact
Surface potential gradients minimized
Minimizes exposure to "step potentials" and "touch potentials"
Other applications include:
Earth screen reflectors
Electromagnetic screening for high frequency installations
Signal reference grids for sensitive communications installations

 

[davedottcom]

Re: Hot Tub sitting on Pavers!

Originally posted by jim sutton:
How about installing your own structural reinforcing steel? The kind that is about 1/8" or 3/16" thick. The steel is already welded together at the cross points.

Do you mean the kind that they use to reinforce concrete floors? (About 6" squares)
I would think that would work great.
680.26(C) says the grid has to be connected with #8 Cu. but the grid itself can be reinforcing steel. That stuff it definately steel, and it's definately used for reinforcing!
I'm pretty sure it is much cheaper then buying or making a copper grid.

Does the NEC get any more specific about the gauge or size of the Steele being used?

 

[jim sutton]

Re: Hot Tub sitting on Pavers!

After some thought, I dont know if this would meet 680.26 (C)(1). This section says "the structural reinforcing steel of a concrete pool".

A hot tub would not be a "concrete pool".

I would look into the product above made by ERICO to be on the safe side.

 

[iwire]

Re: Hot Tub sitting on Pavers!

Dave, Jim that mesh is not corrosion resistant its not acceptable.