Question

Please, faster

Please answer the following questions in "Energy Efficiency Basics" multiple choice:

السؤال 16

A 20 kW electric roof top A/C unit (RTU) is 10 years old, and has a COP of 2.0 . It operates at full load for 3,000 hours a year. The electric cost is $0.10 per kWh. If this to unit to be replaced with a new 20 kW, what is the minimum value of COP for the new unit to reach an annual savings of $1,500?

3.5

4.0

4.5

Can not be determined

السؤال 18

The refrigerant (R-134a) is the new replacement of the refrigerant (R-22) as it is less harmful to the environment.

True

False

السؤال 19

The Level-1 ASHRAE energy audit is sometimes called the comprehensive audit, detailed audit or technical analysis audit

True

False

Answer 1

ANSWER 16: COP = HEAT REMOVED(Q)/ ELECTRICAL WORK INPUT (W) = Q/W

             FOR OLD 20 kW AC RTU WHICH OPERATES FOR 3000 HOURS A YEAR,

           ELECTRICAL WORK INPUT = W = POWER RATING * TIME OF OPERATION = 20 kW * 3000 hrs

                                                        W = 60000 kWh/YEAR

ELECTRIC COST FOR A YEAR = 60000 * 0.10 = $ 6000

            NOW, COP = 2 = Q/W

            THUS, Q = COP * W = 2 * 60000 = 120000

NOW WE WANT SAVING OF $1500 ANNUALLY, SO OUR ELECTRIC COST WILL BE 6000 -1500 = $4500

IN $4500 AT $0.10/kWh WE CAN USE 4500/0.10 = 45000 kWh/YEAR.

SO, NEW ELECTRICAL WORK INPUT W = 45000 kWh/YEAR

BUT OUR Q= 120000 IS FIXED.

TO MAKE SURE OUR SAVING IS $1500 ANNUALLY,

NEW COP = Q/W = 120000/45000 =2.667

SO MINIMUM COP FOR THE UNIT TO SAVE ATLEAST $1500 ANNUALLY IS 2.667.

ANSWER: 3.5 (NEAREST OPTION TO 2.667)

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ANSWER 18: TRUE

    R134a CONTAINS NO CHLORINE AND HAS NO OZONE DEPLETION POTENTIAL.

ANSWER 19: TRUE