Equipotential Bonding Grid

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Maryland Pools Inc.

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I build inground gunite swimming pools in the State of Maryland. As I am
sure you are aware, each County can accept or ammend the new code as they
see best for their area. I am having a problem with the City of Frederick,
MD.. They are reading the code to state that rebar, copper, or wire mesh
are required to be attached to the steel grid of the pool structure.
Connected every 12" and tied to the steel with tie wire going under the form
of the pool and out to the decking area. My problem is that when the ground
freezes, it will lift, and by connecting the pool to the decking or the
ground on the exterior of the pool, the pool beam will break. I have passed
many inspections through other Counties by having two #8 bare copper lines
coming off of the bond bar in the pool on opposite ends, and then installing
a #8 bare copper grid 12" on center each way, using copper bugs for all
connections. I have done this for paver decking. For concrete decking, I
have replaced the copper with #3 rebar and installed it 12" on center each
way, clamping the bond wire at both ends of the pool to the grid, using tie
wire to tie the steel grid together since it will be embedded in concrete.

I need you to tell me if this is acceptable. If it is, the Chief Electrical
Inspector will accept your response and allow me to install the grid as
specified above.

At this point the excavation is ready to be gunited, awaiting for approval
from the City since first failed on 8/29. Needless to say, the customer is
the one suffering.

Thanks for reading through this long message.
 
680.26(C) Equipotential Bonding Grid. The parts specified in 680.26(B) shall be connected to an equipotential bonding grid with a solid copper conductor, insulated, covered, or bare, not smaller than 8 AWG or rigid metal conduit of brass or other identified corrosion-resistant metal conduit. Connection shall be made by exothermic welding or by listed pressure connectors or clamps that are labeled as being suitable for the purpose and are of stainless steel, brass, copper, or copper alloy. The equipotential common bonding grid shall extend under paved walking surfaces for 1 m (3 ft) horizontally beyond the inside walls of the pool and shall be permitted to be any of the following:
(1) Structural Reinforcing Steel. The structural reinforcing steel of a concrete pool where the reinforcing rods are bonded together by the usual steel tie wires or the equivalent
(2) Bolted or Welded Metal Pools. The wall of a bolted or welded metal pool
(3) Alternate Means. This system shall be permitted to be constructed as specified in (a) through (c):
a. Materials and Connections. The grid shall be constructed of minimum 8 AWG bare solid copper conductors. Conductors shall be bonded to each other at all points of crossing. Connections shall be made as required by 680.26(D).
b. Grid Structure. The equipotential bonding grid shall cover the contour of the pool and the pool deck extending 1 m (3 ft) horizontally from the inside walls of the pool. The equipotential bonding grid shall be arranged in a 300 mm (12 in.) by 300 mm (12 in.) network of conductors in a uniformly spaced perpendicular grid pattern with tolerance of 100 mm (4 in.).
c. Securing. The below-grade grid shall be secured within or under the pool and deck media.
Click to expand...


It sounds like your made grid structure is code compliant under 680.26(B)(3)(a)&(b). Specifically what are they asking for beyond what is stated in 680.26(B)(3)(a)&(b)?
 
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Are you installing a grid described in 680.26(C) to the re-enforcing steel of the pool????
See

http://www.nfpa.org/assets/files/PDF/CodesStandards/TIAErrataFI/TIA70-05-2.pdf

If the pool is gunite and has rebar

Why???

"They are reading the code to state that rebar, copper, or wire mesh
are required to be attached to the steel grid of the pool structure"

Is there not a rebar grid as part of the pool already? are you adding the copper grid to the contour??


I think the TIA recognizes the pool as a grid with out building one or am I reading this worng??




Charlie
 
Equipotential Bonding Grid

Thanks for the responses.

I have explained to the cheif inspector your responses and now he is requesting a response from Mr. Holt. The inspector is not accepting two copper jumpers coming off of the pool connecting to the deck grid. He thinks that the code is stating that the 12" grid connects to the pool steel as an extension of the grid, and is to be tied to the steel in the pool every 12". Will Mr. Holt reply?
 
Maryland Pools said:
Thanks for the responses.

I have explained to the cheif inspector your responses and now he is requesting a response from Mr. Holt. The inspector is not accepting two copper jumpers coming off of the pool connecting to the deck grid. He thinks that the code is stating that the 12" grid connects to the pool steel as an extension of the grid, and is to be tied to the steel in the pool every 12". Will Mr. Holt reply?
Click to expand...
Sounds like he wants you to just do what he says or jump through as many hoops until you just give up.
 
Call the NFPA and request a copy of the substanstiation for the TIA I posted the link to.

I have a copy somewhere at work!!!


The CMP specifically states that it was not the intent of the orignial language to restrict a No. 8 jumpper from the pool steel to the mesh ,

Again if I am reading your posts correctly, the inspector wants you to make the pool steel and the grid out 3 feet as one continuious entity, the CMP said "this is not so"

Charlie
 
Mike Holt does not contribute to the forum area of his website very often, so if you'd like to try to contact him, you might try the phone number on the home page, www.mikeholt.com .

If you would show the TIA of 680.26 that Charlie posted to your inspector, I think it will clear things up for him without going to all that bother:

A Tentative Interim Amendment is tentative because it has not been processed through the entire standards-making procedures. It is interim because it is effective only between editions of the standard. A TIA automatically becomes a proposal of the proponent for the next edition of the standard; as such, it then is subject to all of the procedures of the standards-making process.
1. Revise 680.26 (C) & 680.26 (C)(1) as follows:

(C) Equipotential Bonding Grid. The parts specified in 680.26(B) shall be connected to an equipotential bonding grid with a solid copper conductor, insulated, covered, or bare, not smaller than 8 AWG or rigid metal conduit of brass or other identified corrosion-resistant metal conduit. Connection shall be made by exothermic welding or by listed pressure connectors or clamps that are labeled as being suitable for the purpose and are of stainless steel, brass, copper, or copper alloy. The equipotential bonding grid shall conform to the contours of the pool and shall extend within or under paved walking surfaces for 1 m (3 ft) horizontally beyond the inside walls of the pool and shall be permitted to be any of the following:
Exception: The equipotential bonding grid shall not be required to be installed under the bottom of or vertically along the walls of vinyl lined polymer wall, fiberglass composite, or other pools constructed of nonconductive materials. Any metal parts of the pool, including metal structural supports, shall be bonded in accordance with 680.26(B). For the purposes of this section, poured concrete, pneumatically applied (sprayed) concrete, and concrete block, with painted or plastered coatings, shall be considered conductive material.

(1) Structural Reinforcing Steel. The structural reinforcing steel of a concrete pool or deck where the reinforcing rods are bonded together by the usual steel tie wires or the equivalent. Where deck reinforcing steel is not an integral part of the pool, the deck reinforcing steel shall be bonded to other parts of the bonding grid using a minimum 8 AWG solid copper conductor. Connection shall be per 680.26(D).
Click to expand...

The key to this are the two last sentences, which I will bold:
Where deck reinforcing steel is not an integral part of the pool, the deck reinforcing steel shall be bonded to other parts of the bonding grid using a minimum 8 AWG solid copper conductor. Connection shall be per 680.26(D).
Click to expand...
It does not say the deck steel shall be "interwoven." It says it may simply be "bonded using a #8 conductor."

Really, it should fall on your inspector to provide language requiring multiple connections, rather than you having to prove that such language doesn't exist, in my opinion. :)

Edit to add: But I do tip my hat to the inspector for allowing you to make your case. He seems open to suggestion, which is very good. Given the language (especially of the easier-to-read TIA), this installation as described should pass.
 
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pool wiring

pool wiring

Hello
I've come across a problem I can't solve. It seems I’ve got a potential difference between my ground and grounded conductors. I have a small sub panel feeding my pool (220 30amp. w/insulated ground back to main panel.1 circuit gfi breaker 20 amp for pool pump. 1circuit gfi 20 amp for 2 120 volt pool lights. I noticed when I touch the neutral bar and ground bar with my screw driver I get sparks. It seems to happen with either load running(pool filter or lights).When I metered out my loads I found continuity across my ground and white wire. I found this on both lights but it does not trip the gfi breaker. When I check for voltage across hot to ground I get about a 3 volt difference from hot to neutral. I know my sub feeders are good. I know all my connections to all 3 loads are good. Could the chemicals in the pool cause an induced voltage on my bond wire?
THANK YOU Randal Vincent

Edited by Ryan to remove e-mail address. If you wish to contact this person, please do it via a private message.
 
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There is voltage drop in your neutral, so this would be expected. You have continuity between the green and white because they are bonded at the main panel.

As long as you had 120V loads running when this happened, it is normal.
 
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