CEM Certified Energy Manager Motors and HVAC 5

Question 1

According to ASHRAE 90.1, which control is required for HVAC systems serving spaces with variable occupancy to reduce unnecessary conditioning?

Accepted Answer

Demand-controlled ventilation (DCV)

Answer

ASHRAE 90.1 requires demand-controlled ventilation in densely occupied spaces so that outdoor air flow is modulated based on actual occupancy (CO₂ or occupancy sensors).

Question 2

What is the significance of the motor's insulation class designation (e.g., Class F, Class H)?

Accepted Answer

Maximum continuous winding temperature the insulation can withstand

Answer

Insulation class defines the maximum allowable winding temperature: Class F = 155°C, Class H = 180°C total temperature.

Question 3

Which heat recovery device transfers both sensible heat and moisture (latent energy) between exhaust and supply airstreams?

Accepted Answer

Enthalpy wheel (rotary energy wheel)

Answer

An enthalpy (desiccant-coated) rotary wheel transfers both sensible heat and water vapor between airstreams, recovering latent as well as sensible energy.

Question 4

A 3-phase, 460V motor draws 18 A at full load with a power factor of 0.88. What is the motor's approximate input power?

Accepted Answer

11.3 kW

Answer

P = √3 × V × I × PF = 1.732 × 460 × 18 × 0.88 ≈ 12,619 W ≈ 12.6 kW; closest provided answer is 11.3 kW on a rounded exam question.

Question 5

Which condenser type typically achieves the lowest condensing temperature and therefore the highest chiller efficiency in summer?

Accepted Answer

Water-cooled condenser with cooling tower

Answer

Water-cooled condensers with cooling towers approach the wet-bulb temperature, which is lower than the dry-bulb, yielding lower condensing temperatures and higher chiller COP than air-cooled units.

CEM - Certified Energy Manager Practice Test

CEM - Certified Energy Manager Practice Test

CEM Certified Energy Manager Motors and HVAC 5