3e151 B Set Vol 4

100 Questions | By Enorab | Updated: Mar 22, 2022 | Attempts: 623

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UREs for B set of 3E151 cdcs Vol 4.

Questions and Answers

1.

In air distributions systems, the three basic categories of fans are
- A.
  
  Backward inclined, airfoil, and forward curve
- B.
  
  Radial blade, centrifugal, and tubular inline
- C.
  
  Centrifugal, special design, and axial
- D.
  
  Propeller, tubeaxial, and vaneaxial
2.

What are the width and inlet constructions of centrifugal fans?
- A.
  
  SWSI and DWDI
- B.
  
  SWDI and DWSI
- C.
  
  SPST and DPDT
- D.
  
  SPDT and DPST
3.

The purpose of the vanes of a vaneaxial fan is to
- A.
  
  Change the fpm
- B.
  
  Change the cfm
- C.
  
  Increase the torque
- D.
  
  Straighten out the air's spiraling motion
4.

A fan drive is an assembly made up of
- A.
  
  A motor sheave, fan sheave, and connecting belts
- B.
  
  Grooves used to increase and decrease the speed of the fan
- C.
  
  Fixed bores that allow the sheaves to fit the shaft exactly
- D.
  
  Movable discs to increase or decrease the pitch diameter
5.

To prevent needless problems to your heating, ventilation, air conditoner, and refrigeration (HVAC/R) equipment, which items should you check during V-belt inspections?
- A.
  
  Outside diameter
- B.
  
  Proper alignment
- C.
  
  Pitch length
- D.
  
  Belt alignment
6.

The most common size of V-belts used in HVAC systems are
- A.
  
  1L, 2L, and 3L
- B.
  
  3L, 4L, and 5L
- C.
  
  A through D
- D.
  
  A and B
7.

What is generally the proper tension for the top side of fan belts?
- A.
  
  1/2 to 1 inch deflection
- B.
  
  1/2 to 1 1/2 inch deflection
- C.
  
  3/4 to 1 1/4 inch deflection
- D.
  
  3/4 to 1 3/4 inch deflection
8.

A single-duct system become a low-pressure reheat system when
- A.
  
  A higher-pressure duct design and pressure reduction devices are used to permit system balancing
- B.
  
  Heating coils are inserted into the duct system downstream of the cooling coils
- C.
  
  The system responds to only one set of space conditions
- D.
  
  Excess air is dumped into a return-air ceiling plenum
9.

The individual zone or space control is provided in an indution system by
- A.
  
  Heating and secondary airstream
- B.
  
  Careful analysis of the system
- C.
  
  The low-pressure reheat coils
- D.
  
  Inducting the sir
10.

Which multiple-path system uses a mixing valve to control zone temperature by mixing warm and cold air in proper proportion?
- A.
  
  Multizone
- B.
  
  Dual-duct
- C.
  
  Dual-reheat
- D.
  
  Variable-air-volume
11.

What is one way to reduce energy costs if a dual-duct system with no cooling load?
- A.
  
  Replace existing boxes with high-pressure boxes
- B.
  
  Operate the system as a single-zone
- C.
  
  Operate the system as a multizone
- D.
  
  Eliminate the return-air fan
12.

Which multiple-path system meets requirements of the different zones by mixing cold and warm air through dampers at the central HVAC unit?
- A.
  
  High-velocity, dual-duct
- B.
  
  Low-velocity, dual-duct
- C.
  
  Multizone
- D.
  
  Induction
13.

The supply pressure loss data for equipment used in piping systems normally come from
- A.
  
  Manufacturers
- B.
  
  System designers
- C.
  
  HVAC/R technicians
- D.
  
  Velocity head pressure
14.

What is static head?
- A.
  
  Pressure in psi being pumped representing system resistance that must be overcome
- B.
  
  Pressure due to the weight of the fluid above the point pf measurement
- C.
  
  Sum of the lift and velocity head at the pump
- D.
  
  Positive head minus friction head
15.

How many intakes does the single-suction pump impeller have?
- A.
  
  One
- B.
  
  Two
- C.
  
  Three
- D.
  
  Four
16.

Which type pump casing collects water from the impeller and discharges it parallel to the
- A.
  
  Multiple
- B.
  
  Volute
- C.
  
  Diffuser
- D.
  
  Single
17.

Some leakage at the packing gland of a pump is needed to
- A.
  
  Equalize the pressure on the two sides of the seal
- B.
  
  Seal undesirable leakage to the stuffing box
- C.
  
  Allow the coupling halves to be disconnected
- D.
  
  Lubricate and cool the area between the material and shaft
18.

Pumps with mechanical seals
- A.
  
  Can be run dry, depending on the ambient temperature
- B.
  
  Can be run dry, depending on the internal pressure
- C.
  
  Must not be run dry
- D.
  
  Must be run dry
19.

Destructive pitting and wearing of a pump impeller and casing as well as noise and vibration can be caused
- A.
  
  Cavitation
- B.
  
  Friction loss
- C.
  
  Stratification
- D.
  
  Flow coefficient
20.

What is normally the cause of vortex in a piping system?
- A.
  
  Undersized piping
- B.
  
  Too many fittings
- C.
  
  Location of the pump
- D.
  
  Configuration of the piping system
21.

What do manufacturers use to show how pumps respond under different operating condidtions?
- A.
  
  Curves of system pressure changes for different altitudes
- B.
  
  Curves of the temperature and pressure limitations
- C.
  
  A graph of net positive suction pressure head curves
- D.
  
  A performance curve graph
22.

After each major repair to a pump or when there is an indication that the system flow is not correct, what do you check?
- A.
  
  Pump performance
- B.
  
  Mechanical seals
- C.
  
  Stuffing box
- D.
  
  Bearings
23.

What is the maximum allowable working pressure for low-pressure heating boilers with a maximum temperature limitations of 250*F?
- A.
  
  140 psi
- B.
  
  160 psi
- C.
  
  180 psi
- D.
  
  200 psi
24.

What is the usual pressure or medium-pressure heating when the usual design supply temperature is approximately 250*F to 350*F?
- A.
  
  140 psi
- B.
  
  150 psi
- C.
  
  160 psi
- D.
  
  180 psi
25.

What is the maximum allowable working pressure for high-pressure heating boilers with a maximum temperature limitation of 450*F?
- A.
  
  180 psi
- B.
  
  200 psi
- C.
  
  250 psi
- D.
  
  300 psi