Evaporative Condenser Maintenance

Bonar Engineering rarely recommends “post” chemical treatment of sanitary water make-up supplies for evaporative condensers. Municipal and private water supplies which have been treated with chlorine and the use of galvanized metal in the condenser will normally provide adequate “algae” control. We do recommend a bleed-off of at least 1/6 the evaporation rate of water supply. (Some areas, such as California, want to limit this to zero and use oxidizers to drop out “hard” chemicals.) Generally, the use of acids is intended to decrease pH to keep calciums suspended. Municipal waters high in chlorine sometimes are so acidic they will attack metals, even stainless steel, and need to be neutralized with a base such as caustic soda. Control of the pH is obviously the most important aspect of preserving the life of a condenser, and a failure in the treatment method more often causes a shorter life in condensers than no treatment at all. We know of one instance where an owner was paying $60,000 a year for water treatment and getting seven years of life out of condensers. Without any kind of treatment or cleaning, the condensers will often last 15 to 20 years, easily. Alternates to treating include intermediate chemical cleaning and mechanical cleaning.

Both recommended methods of chemical cleaning and mechanical (thermo) cleaning will be discussed in the next issue of Refrigeration Review.