NCT Installation Standards & Best Practices 2

Question 1

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

Accepted Answer

The upstream edge with the gasket side

Answer

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

Question 2

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

Accepted Answer

To prevent unfiltered air from bypassing the filter media

Answer

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

Question 3

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

Accepted Answer

At least one fan wheel diameter

Answer

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.

Question 4

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

Accepted Answer

Air bypass around the filter is occurring

Answer

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

Question 5

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

Accepted Answer

Upstream duct transitions and obstructions

Answer

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

(NCT) NAFA Certified Technician Practice Test

(NCT) NAFA Certified Technician Practice Test

NCT Installation Standards & Best Practices 2