Application Considerations

Figure A-6 - A Comparision of Drain Pan Designs

Figure A-7 - Proper Trapping - Drain Location Examples and Trapping Height Requirements

Water Management. Cooling coils collect water from the passing air stream as they cool and dehumidify it. If not properly addressed, this condensed moisture encourages mold, mildew and other microorganisms to colonize and breed. To reduce the likelihood of microbial growth, apply these guidelines when designing the air handler:

• Reduce moisture carryover by sizing the cooling coils for proper airflow velocities (e.g., typically 350-600 fpm, depending on air conditions and coil fin arrangement).

• Specify drain pans sloped in two directions to eliminate moisture- collecting level seams and promote positive drainage; see Figure A-6.

• Properly size condensate traps as shown in Figure A-7 to ensure proper drainage.

• Promote cleanability — i.e., provide adequate space around the unit, easily removable access panels, and a solid steel liner to isolate insulation from the air stream and facilitate cleaning.

• Specify antimicrobial coatings for filter and drain pan surfaces where moisture is likely to collect. (Though cooling coil surfaces collect water, too, treatment with an antimicrobial coating is discouraged; such coatings greatly reduce the coil’s wetting characteristics and may cause moisture carryover at velocities as low as 200 fpm.)

• Condition mechanical equipment room to minimize condensation on piping, ductwork, mechanical equipment, etc.