What are the characteristics of oil pumps for boilers and engine generators? Select all that apply.

A) They are self-priming.
B) They are positive displacement.
C) They are centrifugal or axial.
D) They use pistons or gears.


A) They are self-priming. , B) They are positive displacement. and D) They use pistons or gears.

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When operating a vehicle with a dual air brake system the driver should

A. Let the vehicle warm up before driving to ensure that the fuel reaches the engine. B. Let the air compressor build up a minimum of 100 psi pressure in the primary and secondary systems before driving. C. Begin driving just after the vehicle starts.

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The coefficient of performance of the refrigeration cycle when operating as an air-conditioner is nearest:

A 5-ton ideal air-conditioner operates between 120 kPa and 800 kPa. The refrigerant is R134a.

A) 3.6
B) 3.9
C) 4.2
D) 4.6

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Technician A says that on steep grades, a hydraulic retarder reduces the load on the conventionalbraking system. Technician B says that hydraulic retarder efficiency runs between 80% and 115%. Who is correct?

A. Technician A B. Technician B C. Both D. Neither

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The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) developed a standard for residential ventilation, commonly referred to as ____.

A. 29.1 B. 43.8 C. 51.5 D. 62.2

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