Installation Standards & Best Practices Flashcards

When installing a filter bank in a horizontal airflow application, which edge of the filter frame should face the incoming air stream?

Answer: The upstream edge with the gasket side

Filters installed in horizontal airflow must present the gasketed upstream face toward the incoming air to ensure a proper seal and prevent bypass.

What is the primary purpose of a filter bypass seal (gasket) in a holding frame?

Answer: To prevent unfiltered air from bypassing the filter media

Gaskets seal the interface between the filter and frame to eliminate bypass leakage, which would allow unfiltered air into the clean air stream.

According to NAFA best practices, how much space should typically be maintained between the final filter bank and the fan inlet?

Answer: At least one fan wheel diameter

NAFA recommends maintaining at least one fan wheel diameter of space between the final filter bank and the fan inlet for uniform airflow distribution across the filter face.

What installation defect is indicated when a differential pressure gauge reads significantly lower than the manufacturer's clean filter resistance specification?

Answer: Air bypass around the filter is occurring

Lower-than-expected differential pressure typically indicates that air is bypassing the filter rather than passing through the media, pointing to a sealing problem.

Which factor most significantly affects face velocity uniformity across a filter bank?

Answer: Upstream duct transitions and obstructions

Duct transitions, elbows, or obstructions directly upstream create turbulent or non-uniform airflow that causes uneven face velocity distribution across the filter bank.

In a multi-stage filtration system, pre-filters should be installed at what MERV range relative to the final filters?

Answer: A lower MERV rating than the final filter

Pre-filters with a lower MERV rating capture larger particles to extend the life of higher-efficiency final filters downstream.

What NAFA installation practice is required when stacking two standard filters to achieve a thicker bed?

Answer: A special double-deep holding frame or adapter must be used

Stacking filters requires a purpose-built double-deep frame to maintain proper support and sealing; improvised stacking creates bypass gaps and structural failure.