CEM Practice Exam Questions with Answers Certified Energy Manager (CEM) Certification

A facility has the thermal cooling load profile shown in the table below. The utility rate tariff has an on-peak time-of-use billing period that begins at 10:00 a.m. and ends at 7:00p.m. Calculate the storage capacity required for a load-shifting operating strategy, to make sure that no thermal cooling Is generated by the chiller during the on-peak utility rate period.

[Question from the previous image, which was about storage capacity for load shifting, but the table was missing]

Using an interest rate of 15%, an energy project has a net-present value (NPV) of $3,500. Which statement is true about the project's internal rate of return (IRR)?

A desk lamp is located inside a windowless office. The office is heated during the winter and cooled during the summer. When the lamp is switched on, how much of the energy consumed by the lamp becomes heat in the office space?

If outside air has a temperature of 30°C dry bulb and 20°C wet bulb, what is the dew point temperature?

What is the purpose of top (or skimming) blowdown in a steam boiler?

What is the purpose of monitoring energy consumption?

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Which of the following instruments is most useful for tracking long-term boiler performance?

What is the main reason for using instrumentation in energy audits?

In a warehouse, lights are mounted 4 meters above the floor. This provides an average light level of 150 lux. To increase the light level without installing more lights or higher Wattage lights, you lower the light fixtures with pendants so that the lights are located 3.25 meters above the floor. Calculate the new average light level on the floor.

Which type of single-phase alternating-current motor has the highest efficiency?

What instrument is NOT used to measure temperature?

A 25-kW motor, at full load, drives a centrifugal fan that produces 160,000 liters per second (l/s) of ventilation air. If the fan speed is reduced to a flow rate of 150,000 l/s, what is the new load on the motor?

Why do electric utility companies transmit power at high voltages?

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An energy-saving project costs $540,000. The project will have maintenance costs of $25,000 per year. The energy savings from the project are $160,000 per year. The project has a life of 10 years with no salvage value. The minimum attractive rate of return (MARR) is 10%. Using end-of-year cash flows, calculate the net-present value (NPV) of the project.

Which type of lighting control technique operates in "manual on" and "auto-off mode, and can be used in situations where there is brief occupancy that do not need lights on?

A 50-kW induction motor (1,500 rpm synchronous speed) has a nameplate full-load rotational speed of 1,455 rpm. Field measurements show the actual rotational speed is 1,475 rpm. Using the slip method, calculate the partial load factor of the motor.

A hot-water boiler has a cut-in set point of 65°C on the hot water supply temperature and a differential set point of 10°C. What is the hot-water supply temperature that causes the boiler to turn off?

What type of passive heat exchanger can wrap around an evaporator coil to precool entering air and reheat the air after the cooling coil without adding more moisture to the supply air stream?

What is a common method to reduce the impact of voltage imbalance?

Which of the following International Performance Measurement and Verification Protocol (IPMVP) options would you use to verify annual energy savings in a project that upgraded lighting in a large manufacturing plant?

Which of the following is NOT a typical benefit of performance contracting from the building owner's perspective?

Using the natural gas combustion efficiency tables in your workbook, find the combustion efficiency (based on higher-heating value) of a natural-gas-fired boiler if the excess air level is measured at 31.9% and the stack temperature rise is 187.8°C.

What instrument determines flow rate by measuring pressure differential?

You are using a performance contract to finance the added cost of using more-efficient equipment in the construction of a new building. Which of the following International Performance Measurement and Verification Protocol (IPMVP) options would you use to verify annual energy savings?

How does an enthalpy-based economizer control operate?

A 3 MW rated wind-powered turbine has a rotor diameter of 113 meters. What is the efficiency of the wind turbine at rated power if it is operating in wind power calculated at 8.6 MW? Assume an air density of 1.225 kg/m³.

If the initial design process includes group relamping, how can this reduce the number of lamps required to illuminate a space?

Which of the following steam turbines will likely not provide steam output at a useable temperature for industrial processes?

How much energy (kJ) is required to heat 2 kg of water from 25°C to 2 kg of water at 100°C? (The specific heat of water (C) is 4.2 kJ/kg-°C. Assume no system losses.)

Electricity costs SO. 10 per kWh. if an electric water heater has an efficiency of 95*6. what is the equivalent price of natural gas per Gigajoule for a natural gas water heater? The natural gas water heater has an efficiency of 95*t based on lower-heating value.

[Natural gas has an energy content of 36.400 K|/m3 (higher-heating value) and 32-760 K/m3 (lower-heating value).]

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Periodic commissioning of a building automation system (BAS) might include which of the following?

The set point for the chiller supply water temperature is varied as a function of the thermal demand for space cooling. What do you call this control strategy?

A 50-Hz alternating current (AC) induction motor has 3 pole pairs (6 poles). What is the synchronous speed of the motor?

When should commissioning be included in the design and construction of a facility?