This invention relates to the art of building construction and more particularly to a condensate drain pan for heating, ventilating and air conditioning (HVAC) units mounted upon the roof.
Butler Manufacturing Company, Kansas City, Mo., manufactures metal roof panels used in building construction. One such panel, sold by Butler under its trademark "MR-24", comprises a 22-24 gauge steel substrate coated with an aluminum-zinc (Al--Zn) alloy. Corrosion of these panels can result when HVAC units drip condensate onto an MR-24 roof for an extended period. We have identified the problem as resulting from copper ions leached by the water from copper tubing in the HVAC units. The copper ions, unless neutralized or removed, react with and corrode the roof panel coating, eventually resulting in rust-through.
While a great deal of attention has been directed over the years to preventing roof corrosion, no inventor, to our knowledge, has specifically tackled or identified the copper ion problem. Rain water is essentially copper-free; the premature corrosion problem arises only with roof-mounted HVAC units.