CEM HVAC Systems & Building Envelope 5

Question 1

A chiller's kW/ton rating is 0.55 at full load and 0.72 at 25% load. What does this indicate about part-load performance?

Accepted Answer

The chiller consumes more energy per ton of cooling at part load

Answer

A higher kW/ton at part load means the chiller uses more electricity per unit of cooling produced at reduced capacity, a common characteristic of centrifugal chillers at very low loads.

Question 2

What is the energy implication of a low 'delta-T syndrome' in a chilled water system?

Accepted Answer

Pumping energy increases because higher flow rates are needed to meet load

Answer

Low delta-T means chilled water returns nearly as cold as it left, so much more water must be pumped to deliver the same cooling tonnage, wasting pump energy.

Question 3

Which of the following roof assembly types provides the greatest reduction in urban heat island effect and cooling load?

Accepted Answer

White TPO membrane cool roof with high solar reflectance

Answer

A white or light-colored membrane (high solar reflectance and thermal emittance) reflects solar radiation rather than absorbing it, reducing roof surface temperatures and cooling loads.

Question 4

A CEM is reviewing a proposed geothermal heat pump system. What is the primary advantage of using the ground as a heat source/sink compared to air?

Accepted Answer

Ground temperatures are more stable year-round than outdoor air temperatures

Answer

Ground temperatures remain relatively constant (50–60°F in most US locations) year-round, allowing the heat pump to operate at consistently higher efficiency than air-source systems that face extreme winter or summer air temperatures.

Question 5

In ASHRAE climate zone 7 (very cold), which wall assembly location for the insulation layer is generally recommended to control moisture?

Accepted Answer

Continuous rigid insulation on the exterior with vapor retarder near the interior face

Answer

In very cold climates, placing rigid insulation outside the structure keeps the sheathing warm (above the dew point) and a vapor retarder near the interior prevents warm moist indoor air from reaching cold surfaces.

(CEM) Certified Emergency Manager Practice Test

(CEM) Certified Emergency Manager Practice Test

CEM HVAC Systems & Building Envelope 5