CEM HVAC and Building Envelope 4

Question 1

What energy efficiency measure does 'supply air temperature reset' provide in a VAV system?

Accepted Answer

Raises supply air temperature at part load to reduce chiller and reheat energy

Answer

Resetting supply air temperature upward during part-load conditions reduces chiller lift energy and minimizes terminal reheat, saving significant energy.

Question 2

What is the primary function of a cooling tower in a water-cooled chiller plant?

Accepted Answer

Reject condenser heat from the chiller to the atmosphere via evaporation

Answer

A cooling tower rejects heat from the chiller's condenser water loop to the atmosphere primarily through evaporative cooling, completing the refrigeration cycle.

Question 3

Which building envelope parameter describes the fraction of incident solar radiation that passes through a window as heat?

Accepted Answer

Solar heat gain coefficient (SHGC)

Answer

SHGC is a dimensionless value from 0 to 1 representing the fraction of solar radiation admitted through a window, both directly transmitted and absorbed then re-radiated inward.

Question 4

A facility engineer wants to reduce pump energy in a chilled water system. Which measure has the greatest single impact?

Accepted Answer

Installing variable frequency drives (VFDs) on pumps

Answer

VFDs reduce pump speed at part load, and because pump power varies with the cube of speed, even small speed reductions yield large energy savings.

Question 5

What is 'sensible heat ratio' (SHR) in HVAC system design?

Accepted Answer

Ratio of sensible cooling load to total (sensible + latent) cooling load

Answer

SHR is the fraction of a zone's total cooling load attributable to sensible heat; it guides coil selection and determines how much dehumidification the system must provide.

(CEM) Certified Emergency Manager Practice Test

(CEM) Certified Emergency Manager Practice Test

CEM HVAC and Building Envelope 4