Energy Conservation Techniques Flashcards

An operator notices the building's HVAC runs at full occupancy settings on weekends when the building is empty. What is the most cost-effective first step?

Answer: Program setback/setup schedules in the BAS for unoccupied periods

Scheduling setback and setup temperatures during unoccupied hours is a no-cost or low-cost measure that cuts runtime substantially.

According to the fan affinity laws, reducing fan speed by 20% reduces fan power consumption by approximately how much?

Answer: 49%

Power varies with the cube of speed, so 0.8³ ≈ 0.51, which is roughly a 49% reduction.

Which economizer control strategy uses both outdoor air temperature and humidity to decide when to use free cooling?

Answer: Enthalpy-based

Enthalpy economizers compare total heat content (temperature plus moisture), which avoids bringing in humid air that only looks cool.

A demand-controlled ventilation (DCV) system typically adjusts outdoor air intake based on which measurement?

Answer: Space CO2 concentration

DCV uses CO2 levels as a proxy for occupancy and lowers ventilation when fewer people are present.

What is the main energy benefit of resetting chilled water supply temperature upward during mild weather?

Answer: It improves chiller efficiency by reducing compressor lift

A higher chilled water setpoint reduces the pressure difference the compressor must overcome, which lowers kW per ton.

Replacing a 40 W T12 fluorescent lamp and magnetic ballast with a T8 lamp and electronic ballast mainly saves energy because:

Answer: Electronic ballasts and T8 lamps deliver more lumens per watt

T8/electronic ballast systems have higher efficacy (lumens per watt), so they produce similar light at lower wattage.

Which practice reduces peak electrical demand charges without necessarily lowering total kWh consumed?

Answer: Load shifting with thermal energy storage

Thermal storage moves cooling production to off-peak hours, which lowers kW demand at peak times.