Industry experts weigh the wire mesh grid vs. single-wire approach to suppressing stray voltage around pools
When the gavel came down on the 2011 National Electrical Code vote in August, it might as well have been 2007 for the losing side in a long and acrimonious debate over swimming pool bonding requirements. Three years, at least two studies, hours of debate, and pages of correspondence later, wording in the 2008 NEC remained standing and unchanged. What’s new, though, are some fresh and pointed questions. Specifically, was the cause of electrical safety sacrificed on the altar of expediency, the cold calculus of cost-benefit analysis, and an overarching “less-is-more” approach to regulations and mandates? Or, did the outcome merely offer proof that the NEC revisions system works as intended?
At issue was code language in Sec. 680.26(B)(2), relating to equipotential bonding around the decks of many in-ground pools. In 2007, during the final months of the 2008 NEC revision cycle, wording in the 2005 Code that mandated an equipotential copper wire mesh grid to suppress stray voltage around pools built without traditional concrete/rebar decks was supplemented with an alternate means. Language specifying a new, alternate method of bonding — a single No. 8 solid wire installed around the perimeter of such pools — was inserted.
No sooner was the ink dry on the 2008 NEC than critics of the reversal began mobilizing. A loose affiliation of parties that had voiced concern about the adequacy of the single wire as a means of preventing shocks and how the change was made soon coalesced, embarking on an ultimately fruitless three-year battle to restore the 2005 wording. Their efforts hit a dead end in August, however. When the National Fire Protection Association’s (NFPA) Standards Council voted to deny an appeal of an NEC Code Making Panel’s near-unanimous recommendation to retain the 2008 single-wire provision — overriding support for the 2005 wording expressed by other NFPA bodies — grid backers had lost.
Now, the critics warn, pool owners remain at greater risk than ever of electric shock — and for no legitimate reason. Despite study findings and testimony that point to the single wire’s deficiencies, grid proponents say, the Code Making Panel that took up the issue either bent to pressure from pool industry interests concerned about costs or failed to appreciate the weight of the evidence. Whatever the reason, critics claim it passed up a chance to give pool owners a better margin of safety.
“This was a setback for those of us who wanted to see safer pool construction,” says Charles DeNardo, chief engineer with WE Energies, a Milwaukee-based electric utility and an expert on stray and contact voltage who lobbied the panel. “There had been a Code requirement for a wire mesh grid, and it was removed. Based on my own experience, I know that a grid is a safer equipotential bonding solution than a single wire.”
But single-wire supporters see it differently. Their case rested largely on real-world evidence. Lacking sufficient documentation of actual high-voltage electrical shock incidents traceable to improper pool bonding — and charged with recommending changes only when there’s compelling evidence an unsafe condition exits — Code Making Panel 17, they argue, made the logical decision.
“The panel is made up of many technical experts, and they reviewed all of the information that was presented,” says Jennifer Hatfield, government affairs associate for the Association of Pool & Spa Professionals (APSP), a group that wanted the Code’s single-wire language retained. “They saw no substantive information that a grid was necessary. They agreed with us that a single wire is sufficient and provides the level of protection that’s needed.”
Studies assess options
Grid advocates, however, argue the scientific evidence was on their side. Their first volley came in August 2008 in the final days of the 2008 NEC revision process, in the form of a study conducted by Georgia Tech’s National Electric Energy Testing Research and Applications Center (NEETRAC), Forest Park, Ga. Commissioned by a pool bonding and grounding equipment supplier, the study would become grid supporters’ star witness.
In a test pool made of fiberglass with a fibercrete lip surrounded by stone pavers, NEETRAC set up two scenarios: an equipotential copper bonding grid encircling the pool 3 ft out from the side (bonded to a pool light, pool water, and pool equipment); and a No. 8 AWG solid copper wire buried 6 ft deep and 24 in. from the pool’s edge (similarly bonded).
Applying 95V between the pool ground and a current return rod, water-to-deck and step voltages were measured in each setup. The grid was found to reduce water-deck voltages between 70% to 93%, compared to voltages measured with the ground ring. The grid also reduced step voltages in a range of 57% to 97%, compared to the ring.
In a carefully worded conclusion in the study write-up, NEETRAC came down on the side of the grid, saying the data “proves unequivocally” that a grid “can and will effectively mitigate” the voltages tested and “provide adequate protection to the swimmer and person walking on the deck.” As for the ground ring, NEETRAC hedged somewhat, saying the study found it “may not provide adequate protection.”
Their case also was bolstered by a later study done by the Electric Power Research Institute, Palo Alto, Calif., an independent, nonprofit company performing research development and demonstration in the electricity sector. The utility industry-funded group compared various pool bonding options and possible fixes for existing pools where stray voltage problems have surfaced. Although it was more multi-faceted and nuanced than NEETRAC’s study, EPRI’s research did suggest that some sort of a bonding grid configuration offered the highest margin of safety, says Douglas Dorr, EPRI senior project manager.
EPRI concluded that a wire mesh embedded in a concrete deck, properly bonded, was the best way to maintain “near equipotential” between the pool deck and pool water. Lacking that, double or triple ground rings tied to a ground rod provide a method of reducing voltage differential. But a single ground ring embedded in concrete within 30 in. of the pool water, it cautioned, may only provide reasonable neutral-to-earth voltage mitigation “where nearby distribution faults are not a concern.”
Panel holds firm
From the outset, however, the research failed to sway the Code Making Panel. Questioning methodologies and the significance of conclusions in light of a lack of demonstrable, real-world safety issues, the panel consistently voted down motions to restore the grid provision in deliberations on both the 2008 and 2011 NEC. With a 6-to-3 vote in 2008, it rejected a temporary interim amendment (TIA) request that would have restored the grid provision in the 2008 Code as an emergency fix. Throughout 2011 Code deliberations, when it was again introduced, the panel’s votes were nearly unanimous.
Even after NEETRAC reiterated its findings, stating in a letter to the panel in March 2010 that “We are not aware of any tests of a single wire or data that would prove it to be safe…the single wire was never intended to stand alone (without ground rods attached) as the 2008 version allows,” and in spite of an NFPA membership general session and NFPA electrical section vote in favor of restoring the grid language at NFPA’s annual conference in June, the panel stood firm. Following NEC revisions protocol that gives deference to Code Making Panels’ deliberations and votes, NFPA’s Standards Council overturned the NFPA floor vote, sending the amendment down to final defeat.
One member of the panel, while opposed to the single-wire provision himself, nonetheless said its decision is defensible in the context of its duties and responsibilities. Based on the facts presented and its charge to recommend Code changes based on clear safety considerations, the panel, says Bruce Hirsch, management consultant with Baltimore Gas & Electric and the electric utility industry’s official liaison to the panel, arguably made the right call.
“Proponents of the grid made good points, but they didn’t show us that the existing methodology didn’t work,” Hirsch says. “I don’t think anyone on the panel will say that the single wire is better than the grid, but they weren’t convinced the single wire doesn’t provide the level of basic, sufficient protection that’s needed. Solutions in the NEC aren’t necessarily the best in every case, but they’re considered to be safe.”
While they may have justifiably seen it coming, some grid backers said they were left feeling dazed after the decision. Supporters like Wayne Robinson, a former chief electrical inspector who took the point on an appeal of the panel’s votes, were left feeling frustrated. He pins most of the blame on coordinated pool industry opposition that helped slip the original change in and pressed the issue as it took up the 2011 NEC.
“I stood up in Boston during the NFPA’s NEC 2008 meeting and told them they didn’t have the documentation to support a single wire, and I brought that up again in Las Vegas [site of the NFPA national convention] this year,” Robinson says. “They claimed to have had some tests done on the single wire, but we never saw the data. In 45 years of working in the electrical industry, I had never seen the NEC lower the level of safety without documentation.”
The panel’s chairman, Don Jhonson declined to comment on the panel’s decision on one occasion. He also did not return a later follow-up call for comment.
Weighing the evidence
Pool industry technical experts and professionals maintain the single wire and the grid have been tested — over time and under real-world conditions. Carvin DiGiovanni, APSP senior director, technical and standards, says because pool installers have used both methods with the same real-world results, the single wire is a proven-effective option. A grid may also work, and some installers may choose it, he adds, but the industry’s chief concern was losing access to options.
“We’re saying that the single wire has been shown to work for our industry, and we want that option preserved,” he says. “Our technical guys did look at the NEETRAC study, but they determined it didn’t provide definitive, overwhelming information in support of a grid as the only solution.”
Comfortable with the single wire, pool industry players were concerned that needlessly returning to a grid mandate would add costs and reduce flexibility, DiGiovanni says. Requiring larger quantities of increasingly expensive copper and the added labor needed to lay a grid, this group worried that a new cost burden could hurt an already strained industry.
Some took issue with grid supporters’ claims that a grid would add just a couple of hundred dollars to the cost of a pool. With the current price of copper, sold in rolls, pool builder John Garner, owner of Pools By John Garner, Jacksonville, Fla., and president of the northeast chapter of the Florida Swimming Pool Association, which has been actively engaged in the bonding debate, guessed materials alone for a typical pool grid might exceed $1,000. David Pruette, an electrical contractor in Orange Park, Fla., who works with installers like Garner, says having to pay extra for something of questionable utility doesn’t make sense.
“It’s not an easy thing to circle a pool with a grid of wire, and while I could see where a grid might conceivably be safer, as far as I know, no one can point to a case where someone has been hurt because a single wire was used,” he says. “It’s kind of like choosing to drive a tank down I-95; you’re safer than driving a VW, but is it necessary?”
Grid advocates unequivocally say, “yes.” High and potentially dangerous levels of stray voltage in residential areas is a growing problem (see Conditions Might be Right for More Pool Shocks). Outdoor pools that aren’t properly bonded are increasingly risky environments. Installers should use bonding techniques that demonstrate the highest levels of safety — not those presumed to work based on past performance as judged by documented, demonstrable shock events, they say.
Looking backward and forward
With the 2011 NEC in place, both sides appear to have retreated to their corners. For many in the pool industry, there’s relief that the freedom to bond pools with a single wire has been protected — and a sense that the NEC revisions process worked, aided by common-sense arguments made by industry interests.
“We haven’t had a huge lobby like other industries, but we’ve gotten more proactive on issues like this,” Garner says. “We have some very knowledgeable people in place now in our industry associations who can intercept issues like this and say ‘Hey, wait a minute, why are we doing this?’ This was something that could have ended up raising costs to the consumer for no logical reason.”
On the losing side, grid advocates remain convinced that pool safety has been compromised. While they blame pool industry interests for mounting opposition, they’re equally critical of the NEC revisions process. When one body — a Code Making Panel represented by industry interests — effectively wields the power to overrule decisions other equally competent NFPA bodies make based largely on hard evidence, the system may be broken, they suggest.
Robinson complains he was asked to jump through hoops to file appeals and argue his case multiple times, only to have procedural rules invoked, allowing the Code Making Panel’s earlier vote to trump everything. It leaves him wondering if the outcome wasn’t preordained.
“My interest all along in this was that the NEC lowered the level of safety in the 2008 Code and that restoring the grid was a way to lower the risk,” he says. “Both NEETRAC and EPRI say the single wire doesn’t work, but the panel continued to believe it wasn’t an issue. I felt the change was going to happen after we submitted more documents, but it didn’t seem to sway them. It leaves me feeling that the NFPA process may be flawed.”
But there’s still talk of regrouping. Robinson says he’s mulled doing an end run around the NEC, and seeing if the issue could be addressed in the International Residential Code. Others, like EPRI’s Dorr, who in October completed another round of testing he says bolsters the case against the single wire, talks of inviting pool industry interests to witness live testing as a basis for further discussion. Even APSP’s DiGiovanni leaves the door ajar, suggesting more comparative tests, research, and hard data might be needed to resolve the issue to everyone’s satisfaction. Meanwhile, even with each side heavily invested in its position, there’s a palpable sense of the fear both feel: more documented pool shock incidents.
“One person getting shocked is a problem as far as I’m concerned,” says DeNardo.
Zind is a freelance writer based in Lee’s Summit, Mo. He can be reached at firstname.lastname@example.org.