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NAFA Guide To Air Filtration

Learn about different types of air cleaners, including media and electronic air cleaners. Understand service requirements, efficiency factors, design considerations, and standards for operation. Discover solutions like washable electronic air cleaners and agglomerator units for dust disposal.

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NAFA Guide To Air Filtration

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  1. NAFA Guide To Air Filtration Chapter 6 Air Cleaners presented by the National Air Filtration Association Fifth Edition

  2. Air Cleaners • Different types of air cleaners - Media • Electronic Air Cleaners (aka-- Electrostatic Precipitators • Agglomorators • Service requirements for air cleaners • Standards for operation

  3. Media Air Cleaners • Most media-type air cleaners use HEPA filters and molecular (activated carbon) afterfilters to clean the air.

  4. Media Air Cleaners • Air cleaners also come in whole-house residential styles that add-on to the existing HVAC unit

  5. Electronic Air Cleaners Two-stage electronic air cleaners utilize: • an ionizer section • a collector section

  6. Efficiency • The ASHRAE 52.2 filter test method has no specific procedure for testing the loading of electronic air cleaners – carbon fouls units • The efficiency is highest when the plates are clean. • Velocity and humidity sensitive.

  7. Prefilters • Low-efficiency air filters upstream of an electronic air cleaner: • Filters will act as air distribution panels to equalize the airflow. • Will capture large particles that could bridge the plates and cause a short or arcing • excessive power consumption • snapping noise • Elimination of arcing helps control ozone generation.

  8. Factors Affecting ESP Design & Efficiency • Their successful use depends on the following: • Particle Size • Velocity through the filter • Voltage on Ionizer and Collector • Collector Plate Spacing • Collector Plate Loading • Ionizer Spacing • Ozone

  9. Service Requirements • Electronic air cleaners should be designed for easy cleaning. • Important design considerations: • Insulators: high quality arc-resistant material and mounted out of the airstream. • Easy access to the ionizer and collector cells. • Some provision for isolating a section in large multi-component units if one becomes defective.

  10. Standards for Electronic Air Cleaners • UL 867 “Standard for Electronic Air Cleaners: Unites States • Covers electrical and fire safety requirements. • It makes no comment about the air-cleaning ability of electronic air cleaners • CSA C22.2 No. 187-Mi986 Canadian Standard: • Specifically states (Par.i.5) that the Standard does not specify the effectiveness of air cleaners with respect to the removal of airborne particles. • Association of Home Appliance Manufacturers Association (AHAM) AC-1-2006

  11. Applications Not Suitable forElectronic Air Cleaners • Conditions of very high humidity • Systems where there can be a build up of explosive gases. • Unattended equipment where periodic maintenance procedures are not assured.

  12. Commercial ESP

  13. Dust Disposal • The removal of dust that an electronic air cleaner has captured can be accomplished in two ways: • It can be washed off the collector plates. • If it has agglomerated on the plates, it can be allowed to blow off the plates. The blow-off is then captured by a mechanical filter downstream of the agglomerator cells

  14. Washable Electronic Air Cleaners • When the collector plates became loaded with dust so that the performance of the electronic air cleaner is reduced, the power is shut off and the plated are washed.

  15. Washing • Removable component assemblies. • Washing tanks • Manual wash in place. • Power spray with detergent • Automatic wash in place. • Built in spray nozzles • Mobile washers. • Large installations

  16. Agglomerator Unit

  17. Agglomerator Units • Dry collector plates with a strong bond between the small dust particles and the collector plates. • The particles on the plates form agglomerates. • As the agglomerates grow larger, their attraction to the plate is reduced and finally these agglomerates may be introduced back into the airstream.

  18. Afterfilters • Automatic Roll Filters • Capture agglomerates – larger particles • Because the face velocity is not uniform, it can cause variations in efficiency. • Extended Surface Filters • MERV 14 • More uniform air flow creates conditions for the agglomerator to operate at optimum efficiency.

  19. Sample Questions • Electronic Air Cleaners cannot be tested for loading using the ASHRAE 52.2 test because? The carbon in the Test Dust shorts out the electrical connections of the unit. • One advantage of a self-contained ESP is? Washable cell/capture of smaller particles/good for source capture/portable

  20. Thank you. Other Questions ?

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