AFE Energy Management & Sustainability 5 â Questions and Answers
Question 1: A facility's boiler stack temperature has increased by 50°F over the past year with no change in load. What is the most probable cause?
- Increased combustion air supply improving fuel efficiency
- Fouled heat transfer surfaces (soot or scale) reducing heat absorption (Correct answer)
- Higher natural gas heating value increasing flame temperature
- Reduced steam pressure setpoint allowing more flue gas heat recovery
Correct answer: Fouled heat transfer surfaces (soot or scale) reducing heat absorption
Fouled boiler tubes act as insulators, preventing heat transfer to the water/steam and allowing more heat to escape up the stack, raising flue gas temperature and reducing efficiency.
Question 2: In a retro-commissioning (RCx) project, what distinguishes it from a standard energy audit?
- RCx focuses exclusively on capital-intensive equipment replacements
- RCx identifies and corrects operational deficiencies in existing systems without major capital investment (Correct answer)
- RCx requires a full building simulation model before any findings can be reported
- RCx is only applicable to buildings less than 5 years old
Correct answer: RCx identifies and corrects operational deficiencies in existing systems without major capital investment
Retro-commissioning systematically investigates and corrects how existing building systems are operatingâsuch as control sequences, scheduling, and setpointsâtypically with low-cost operational improvements.
Question 3: Which federal program provides a voluntary energy performance certification specifically for industrial manufacturing plants in the US?
- LEED for Operations & Maintenance
- ENERGY STAR for Industry / Superior Energy Performance (SEP) (Correct answer)
- ISO 50001 Mandatory Industrial Compliance
- EPA's Green Power Partnership
Correct answer: ENERGY STAR for Industry / Superior Energy Performance (SEP)
The Superior Energy Performance (SEP) program, aligned with ISO 50001, offers third-party certified recognition for industrial facilities that demonstrate measured energy performance improvements.
Question 4: What is the primary purpose of 'submetering' in a large commercial facility?
- To bypass the utility's main meter for billing purposes
- To measure energy consumption at the system or tenant level for accountability and targeting of savings (Correct answer)
- To reduce the number of electrical panels required by the NEC
- To provide backup measurement in case the utility meter fails
Correct answer: To measure energy consumption at the system or tenant level for accountability and targeting of savings
Submetering breaks total facility consumption into component parts (by floor, tenant, or system), enabling identification of energy waste, tenant billing, and targeting of conservation measures.
Question 5: A rooftop photovoltaic (PV) array generates AC power that exceeds the facility's instantaneous load. What happens under a net metering agreement?
- The inverter automatically shuts down to prevent grid overvoltage
- Excess generation is exported to the grid and credited against future utility bills (Correct answer)
- The excess energy is stored in a mandatory on-site battery system
- The facility must pay the utility a grid interconnection penalty fee
Correct answer: Excess generation is exported to the grid and credited against future utility bills
Under net metering, excess PV generation flows back to the grid and the facility receives a credit (typically at retail rate) that offsets future electricity charges.
Question 6: Which of the following best describes the 'greenhouse gas (GHG) Scope 2' emissions category relevant to facility energy management?
- Direct emissions from on-site combustion sources like boilers and generators
- Indirect emissions from purchased electricity, steam, heat, or cooling consumed by the facility (Correct answer)
- All other indirect emissions from the facility's value chain and supply chain
- Emissions from employee commuting and business travel
Correct answer: Indirect emissions from purchased electricity, steam, heat, or cooling consumed by the facility
Scope 2 covers indirect GHG emissions associated with purchased energyâelectricity, district heating/cooling, or steamâthat is generated off-site but consumed by the reporting organization.
Question 7: A facilities engineer is sizing a replacement chiller and considers the Integrated Part Load Value (IPLV). Why is IPLV more useful than the full-load COP for this application?
- IPLV accounts for refrigerant charge accuracy at nameplate conditions
- Most commercial chillers operate at partial load the majority of the time, making IPLV more representative of real-world efficiency (Correct answer)
- IPLV is required by code for all chiller replacements above 100 tons
- Full-load COP cannot be measured accurately in the field
Correct answer: Most commercial chillers operate at partial load the majority of the time, making IPLV more representative of real-world efficiency
Commercial chillers rarely operate at full load; IPLV weights efficiency at 25%, 50%, 75%, and 100% load conditions to better represent annual energy consumption under typical operating profiles.
AFE Energy Management & Sustainability 5
A facility's boiler stack temperature has increased by 50°F over the past year with no change in load.
What is the most probable cause?