An important question to consider is, “Does the copper tubing of the radiant panel installation being in direct contact with the #10 steel wire mesh create any problem with tubing degradation and subsequent premature failure?” We say it does not and others agree. Mr. John Peery was Director of Engineering for AT&T;, the Western Division of the United States. He’s a brilliant engineer in the field of low voltage electrical engineering. As the Director, he was responsible for 1,060 engineers in the company. We have consulted with him and several other chemical and mechanical engineers regarding our installation parameters and the problems with tubing degradation. In every instance all of them agree with our arguments that are to follow.
What is galvanic corrosion, electrolysis, and hydrolysis? Galvanic corrosion is an accelerated corrosion of a metal because of an electrical contact with a more noble metal or nonmetallic conductor in a corrosive environment. Electrolysis is the production of chemical changes of the electrolyte by passage of current through an electrochemical cell. Finally, hydrolysis is: 1) the decomposition or alteration of a chemical substance by water; 2) in aqueous solutions of electrolytes, the reactions of cations with water to produce weak bases or anions to produce weak acids.
In all of the above classical definitions there are three common items: electrical current; corrosive electrolyte; and dissimilar metals. In order for the reactions which cause degradation of the copper tubing to occur, all three aspects, i.e., electric current, corrosive electrolyte, and dissimilar metals must exist. THIS IS A THREE PART EQUATION. If you eliminate one part, the reactions simply cannot occur. This is an undeniable scientific fact and substantiated by many years of hands-on examination of hundreds of copper tubes removed during leak repairs. ANDERSON RADIANT HEATING has never observed one case in over 46 years where any copper radiant tube when properly installed and encased in the concrete and subsequently attached to a steel wire mesh has exhibited premature failure or been degraded by any of the discussed processes. We challenge anybody, including ICBO or IAPMO members, engineers, or local building officials to produce a single radiant copper tube which when directly attached to a steel wire mesh displays any of these conditions. They can’t! Hydronic Engineers know that any failure of the tubing is always due to other reasons.
In regards to specific residential design parameters, any competent engineer or building official must evaluate these questions. First, where is the electrical current? In our installations, the welded steel wire mesh is not physically attached to any grounded source. It is lifted into the concrete at the time of the concrete pour. Again, where is the electrical current? Please note that an argument it can be introduced by the boiler safety and support equipment would be wrong. The boiler equipment is always dialectically isolated from the domestic water supply of the home. The supply and return piping of the boiler are dialectically isolated from the radiant panel tubing. The pump is dialectically isolated with rubber flanges. The low voltage zone control valves are dialectically isolated via rubber o-rings and flappers in the valves. Again, where is the electrical current? There is none! There cannot be any galvanic corrosion, electrolysis, or hydrolysis in our system design. By eliminating the electrical current and the stray voltages thereof, we have eliminated one part of the equation which is required to produce degradation.
Continuing this analysis, where is the corrosive electrolyte? Our system design is based on the principle of a “closed-loop”. There is no evaporation or the introduction of “new city water” into the tubing system once it has been filled. The entire radiant panel contains about 15 gallons of water. Again, where is the corrosive electrolyte? You might argue it’s in the water. We would certainly agree; however, as any knowledgeable chemical engineer and the Copper Development Association agrees, there isn’t enough corrosive electrolyte in 15 gallons of water to substantially affect a type “L” copper tube. Once the water has been heated, cooled, and distilled by actions of the boiler, the minor amount of electrolytic action or hydrolysis which initially occurs from anion and cation reactions is completely eliminated. Again, where is the corrosive electrolyte? There is none! There cannot be any galvanic corrosion, electrolysis or hydrolysis in our system. By eliminating the corrosive electrolyte through a “closed-loop” system design, we have eliminated a second part of the equation which is required to produce degradation.
In conclusion, we have a three part equation where three prerequisite conditions must all exist to produce galvanic corrosion, electrolysis, or hydrolysis in any radiant panel system. By eliminating 2/3’s of the conditions promoting these processes, the contact between the more noble copper and less noble steel wire mesh actually is beneficial to tubing longevity. If for some unforeseen degradation should occur, the steel mesh would long be destroyed and rusted away before affecting the copper tube. This contact cannot affect the copper performance nor promote premature tubing failure.