EMP Energy Audits 3 — Questions and Answers
Question 1: An energy auditor discovers a facility's compressed air system operates at 120 psi but most end uses only require 90 psi. The BEST recommendation is to:
- Install a larger compressor to maintain stable pressure
- Reduce system pressure to the minimum required level (Correct answer)
- Add a heat recovery unit to the compressor aftercooler
- Replace pneumatic tools with electric alternatives
Correct answer: Reduce system pressure to the minimum required level
Reducing compressed air pressure by 2 psi saves approximately 1% in compressor energy, so dropping from 120 to 90 psi can yield roughly 15% savings.
Question 2: In the context of energy audits, what does 'demand charge' refer to on a utility bill?
- The cost per kWh of electricity consumed during peak hours
- A fee based on the highest rate of power draw during the billing period (Correct answer)
- A surcharge for exceeding the contracted annual energy budget
- The monthly fixed charge for maintaining grid connection
Correct answer: A fee based on the highest rate of power draw during the billing period
Demand charges are based on the peak power demand (kW) during a billing period, often the highest 15- or 30-minute average, and can represent 30–70% of a commercial electricity bill.
Question 3: Which heat transfer mechanism is responsible for the majority of heat loss through a well-insulated opaque wall assembly?
- Radiation through the wall material
- Conduction through the solid materials (Correct answer)
- Convection within wall cavities
- Air infiltration through joints
Correct answer: Conduction through the solid materials
In a well-insulated opaque wall, conduction through the solid materials (studs, insulation, sheathing) is the dominant heat transfer mechanism.
Question 4: A facility manager wants to evaluate the thermal performance of a roof during an energy audit. Which diagnostic tool provides a non-destructive assessment of insulation defects and moisture intrusion?
- Blower door test
- Infrared thermography (Correct answer)
- Ultrasonic leak detector
- Gas chromatography analyzer
Correct answer: Infrared thermography
Infrared thermography detects temperature differences on roof surfaces that indicate missing insulation, thermal bridging, or moisture-saturated insulation without destructive testing.
Question 5: When auditing a steam distribution system, auditors should pay particular attention to steam traps because failed-open traps result in:
- Reduced steam pressure throughout the distribution system
- Continuous steam blowthrough, wasting significant boiler energy (Correct answer)
- Water hammer events that damage piping and equipment
- Increased condensate return temperatures
Correct answer: Continuous steam blowthrough, wasting significant boiler energy
A steam trap failed open allows live steam to pass continuously into the condensate return, bypassing useful heat delivery and wasting substantial boiler fuel.
Question 6: During an energy audit, a facility's cooling tower is found to have a 'cycles of concentration' of 2. Increasing this to 5 would primarily achieve which benefit?
- Reduce fan motor energy consumption by 60%
- Decrease makeup water consumption and associated energy for water treatment (Correct answer)
- Improve the coefficient of performance of the chiller
- Lower condenser water supply temperature to the chiller
Correct answer: Decrease makeup water consumption and associated energy for water treatment
Higher cycles of concentration mean less blowdown and less makeup water needed, reducing water costs and the energy required to pump, treat, and heat incoming water.
Question 7: What is the significance of 'regression analysis' in energy auditing?
- It identifies the age-related degradation rate of HVAC equipment
- It develops a mathematical model relating energy use to independent variables like weather and production (Correct answer)
- It calculates the regression-to-mean effect on lighting controls savings
- It determines the payback period by regressing capital cost against annual savings
Correct answer: It develops a mathematical model relating energy use to independent variables like weather and production
Regression analysis creates a baseline energy model correlating consumption to drivers like heating degree days or production volume, enabling accurate measurement and verification of savings.
EMP Energy Audits 3
An energy auditor discovers a facility's compressed air system operates at 120 psi but most end uses only require 90 psi.
The BEST recommendation is to: