CEM HVAC Systems & Building Envelope 4

Question 1

A facility engineer notes that cooling tower approach temperature has increased over several months. What is the most likely cause?

Accepted Answer

Fouled or scaled fill media reducing heat transfer

Answer

Scale or biological fouling on the tower fill reduces wetted surface area and heat/mass transfer effectiveness, increasing the approach temperature.

Question 2

Under ASHRAE 90.1, what is the primary purpose of the building envelope compliance path using the prescriptive method?

Accepted Answer

Verify that envelope component U-values meet tabulated maximum requirements

Answer

The prescriptive path requires that individual envelope components (roof, walls, windows) meet maximum U-factors and minimum R-values specified in ASHRAE 90.1 tables by climate zone.

Question 3

Which refrigerant property most directly determines the operating pressures of a vapor-compression system?

Accepted Answer

Saturation pressure-temperature relationship

Answer

The saturation pressure-temperature curve dictates the evaporating and condensing pressures at given temperatures, defining compressor lift and system design.

Question 4

A building automation system (BAS) shows supply air temperature consistently 3°F above setpoint. What is the most energy-efficient corrective action to investigate first?

Accepted Answer

Calibrate or replace the supply air temperature sensor

Answer

A faulty sensor is the lowest-cost root cause; sensor drift or failure will cause the control system to maintain incorrect conditions wasting energy before mechanical changes are made.

Question 5

What does the term 'thermal mass' refer to in the context of building envelope performance?

Accepted Answer

Capacity of building materials to absorb and store heat energy

Answer

Thermal mass describes materials with high heat capacity (concrete, masonry) that absorb heat during the day and release it later, moderating indoor temperature swings.

(CEM) Certified Emergency Manager Practice Test

(CEM) Certified Emergency Manager Practice Test

CEM HVAC Systems & Building Envelope 4