Retrotec USACE - Manual (Page 167)

Appendix D D37
small condensate collecting pans under fan coil units and chilled water pipes
with valves, this results in wet ceiling tiles and mold problems as well as exces-
sive cooling energy losses (Figure D61).
D.2.3.14 Ice or Frost Buildup on the Evaporator Coil or
Refrigerant Suction Line
Figure D62. Examples of evaporator coil refrigerant lines freezing and frosting (top left, top
right, bottom left), condenser coil frosting (bottom middle), and ice building up on the fl oor
(bottom right).
In normal operation, an air conditioning system is cooling air by moving it
across a refrigerant-cooled “evaporator coil” or “cooling coil” in the air handler.
Cooling air also removes moisture from the air. Normally the moisture that is
removed from building air forms condensate on the surfaces of the cooling
coil, runs down that surface to a collector pan, and is drained away. If the air
fl ow is too slow across the cooling coil, or if the refrigerant is not being metered
properly into the cooling coil or the refrigerant charge is too low, the compres-
sor operates too long and can cause ice buildup on the cold refrigerant lines
or evaporator coils. The condenser can also ice up from extended run times
and humidity entering the refrigerated space. Ice and frost buildup result in
signifi cantly reduced effi ciency of the cooling system (Figure D62). For more
information on common causes and prevention of icing and frosting, see http://
www.inspect-ny.com/aircond/ACCoil.