Custom coils are available from both large and small air conditioning 

 manufacturers on industrial units that are custom assembled,, The old 

 industry standard, tin-dipped copper coil can be obtained at a premium 

 of 30% to 60%, depending upon the unit; the coil itself costs about 

 three times as much as the standard copper tube/aluminum fin coil„ 

 Because of coil design difference, the increased all-copper coil lifetime 

 is achieved at some possible sacrifice of initial coil capacity and 

 efficiency,, Other metals such as stainless steel are also available „ 

 The least expensive possibility for improved fin corrosion resistance 

 is the use of standard aluminum fin stock pre-coated before fabrication 

 of the fins„ The York Division of Borg-Warner Corporation is investigating 

 Kanigen electroless nickel pre-coating which conforms to MIL-SPEC 26074A. o 



Coil Coating 



If an industry standard for condenser coil coating can be said to 

 exist, based on usage for only a fraction of 1% of the total tonnage, 

 it is Heresite coating„ Heresite provided good protection in the Army's 

 Panama, Canal Zone test,, This coating is applied by a proprietary 

 method developed specifically for finned coils using a baked, phenolic 

 resin base material which conforms to MIL-C-18467A„ The multiple coat 

 finish has a dry film thickness of 3 mils with sufficiently good thermal 

 conductivity that no increased coil surface allowance is recommended for 

 coated coils „ The Trane Co. amd many smaller manufacturers use Heresite 

 for condenser and evaporator coils in corrosive atmospheres „ Coils must 

 be shipped to Manitowoc, Wisconsin, for coating, which typically adds 

 about 50% to the cost of a five-ton unit and 50% to the cost of a fifteen- 

 ton unit,, 



Relative to energy savings in severe marine environments, it is the 

 opinion of Trane Co„ engineers that coil coatings would be less cost 

 effective than periodic condenser washing with fresh water,, Their 

 operating manuals recommend condenser washing at the beginning of the 

 cooling season and once a month thereafter They concur with the 

 conclusion of this analysis that a 15% to 25% increase in power con- 

 sumption over the equipment lifetime is reasonable if regular condenser 

 washing is not part of a station's preventive maintenance progranu 



Many manufacturers of packaged mechanical cooling equipment purchase 

 their condensers from other firms who specialize in coil fabrication,, 

 What limited industry research and development has been done on coil 

 coatings has been done by coil fabricators „ The Bohn Heat Transfer 

 Divison of Gulf £ Western Manufacturing Company, has developed a 

 line of coatings known as Bohn-Kote. Bohn-Kote No„ 1 has been used 

 successfully for dip coating wet condensers in marine environments „ 

 However, it is suitable only for small coils,, It is expensive because 

 the material has a 24-hour maximum pot life. Bohn-Kote Nos„ 2 and 3 

 have been used by other coil fabricators as a substitute for Heresite,, 



48 



