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.
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
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
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