NCT System Maintenance & Troubleshooting 2

Question 1

A technician notices that filter differential pressure readings are unusually low even though the filters appear dirty. What is the most likely cause?

Accepted Answer

Manometer tubing is blocked or disconnected

Answer

Blocked or disconnected manometer tubing prevents accurate differential pressure measurement, resulting in falsely low readings despite dirty filters.

Question 2

During routine inspection, a bag filter shows signs of fabric tears near the seal area. What corrective action should be taken first?

Accepted Answer

Replace the damaged filter immediately to prevent bypass

Answer

Tears near the seal allow unfiltered air to bypass the media, so the filter must be replaced immediately to maintain system integrity.

Question 3

Which parameter should a technician verify first when a HEPA filter system experiences a sudden increase in face velocity?

Accepted Answer

Upstream damper position

Answer

An incorrectly positioned upstream damper can increase the volume of air directed through the filter, causing elevated face velocity.

Question 4

What does a rising differential pressure trend over successive maintenance cycles indicate about filter loading?

Accepted Answer

Filters are reaching end-of-life faster than expected

Answer

A consistently steeper rise in differential pressure with each cycle suggests contaminant loading is accelerating, indicating filters are reaching end-of-life sooner.

Question 5

A HVAC technician finds microbial growth on the downstream side of a cooling coil filter. What maintenance action is most appropriate?

Accepted Answer

Replace the filter and disinfect the downstream surfaces

Answer

Microbial growth on downstream surfaces requires both filter replacement and disinfection of contaminated ductwork to prevent continued proliferation.

(NCT) NAFA Certified Technician Practice Test

(NCT) NAFA Certified Technician Practice Test

NCT System Maintenance & Troubleshooting 2