HVAC Controls Trivia Questions! Quiz

27 Questions | Total Attempts: 252

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HVAC Controls Trivia Questions! Quiz - Quiz

HVAC Controls Final Quiz


Questions and Answers
  • 1. 
    The control result is not monitored for which system? (i.e. The output variable xa of the controlled system has no backward effect on the controlling equipment)
    • A. 

      Open Loop

    • B. 

      Closed Loop

  • 2. 
    A humidification sequence would use what type of controller?
    • A. 

      Direct acting

    • B. 

      Reverse Acting

  • 3. 
    HVAC systems are almost always:
    • A. 

      Non self-regulating (astatic or integral system, I-systems)

    • B. 

      Self-regulating (static or proportional systems, P-systems)

  • 4. 
    The Transfer Coefficient of the Controlled System is represented by
    • A. 

      Tn

    • B. 

      Tv

    • C. 

      Ks

    • D. 

      Kd

    • E. 

      Xh

  • 5. 
    If the control range Xh is too large, then...
    • A. 

      The setpoint can't be achieved if the maximum disturbance variable occurs

    • B. 

      The control loop tends to oscillate

  • 6. 
    In PT1, the 1 refers to:
    • A. 

      One storage element

    • B. 

      One control system

    • C. 

      One slave controller

  • 7. 
    The controllability of a system ___________ with an increasing number of storage elements.
    • A. 

      Increases

    • B. 

      Decreases

    • C. 

      Doesn't change

  • 8. 
    Which of the following is not a way to describe the dynamic response of a controlled system?
    • A. 

      Description via step response

    • B. 

      Description by the Ziegler-Nichols method

    • C. 

      Description by the control variable response

    • D. 

      Description via the frequency response (harmonic response)

  • 9. 
    Information on how the controlled system reacts to a sudden increase in heat gains would be best provided by:
    • A. 

      Manipulated variable step response

    • B. 

      Disturbance variable step response

  • 10. 
    The "correcting span" is:
    • A. 

      Xp

    • B. 

      Xh

    • C. 

      Yh

    • D. 

      Tv

  • 11. 
    The main storage element in an electrically heated hot water tank is the:
    • A. 

      Electric resistance element

    • B. 

      Water

    • C. 

      Agitator

    • D. 

      Thermometer

    • E. 

      Tank Insulation

  • 12. 
    Is dead time the same as travel time?
    • A. 

      Yes

    • B. 

      No

  • 13. 
    If there are a lot of storage elements in the system, the step response:
    • A. 

      Has a steeper slope

    • B. 

      Has a gentler slope

  • 14. 
    Tu, Tg, and Ts are (in order)
    • A. 

      Balancing Time, Delay Time, Time Constant

    • B. 

      Time Constant, Balancing Time, Delay Time

    • C. 

      Delay Time, Time Constant, Balancing Time

    • D. 

      Delay Time, Balancing Time, Time Constant

  • 15. 
    The degree of difficulty S (Tu/Tg) represents:
    • A. 

      The control range of a control system

    • B. 

      The controllability of a controlled system

    • C. 

      The reaction time of a controlled system

  • 16. 
    A difficult-to-control system has a degree of difficulty (S) of:
    • A. 

      S

    • B. 

      S=0.1...0.3

    • C. 

      S>0.3

  • 17. 
    Controlled systems in the ventilation field tend to have ______degrees of difficulty and _________ balancing times when compared to the heating field.
    • A. 

      Higher, longer

    • B. 

      Higher, shorter

    • C. 

      Lower, longer

    • D. 

      Lower, shorter

  • 18. 
    The oscillation test (Ziegler-Nichols method) is performed in what environment?
    • A. 

      Closed Loop

    • B. 

      Open Loop

  • 19. 
    ________ controllers are mainly used for temperature, pressure, or level control.
    • A. 

      Powered controllers

    • B. 

      Self-actuated controllers

  • 20. 
    A direct-acting controller only activates its output if e is
    • A. 

      Less than 0

    • B. 

      Greater than 0

  • 21. 
    Which controller type can position its output variable at two or more pre-defined values within the entire correcting span Yh?
    • A. 

      Two-position

    • B. 

      Modulating

    • C. 

      Non-modulating

    • D. 

      Quasi-modulating

  • 22. 
    The smaller the proportional band Xp that is selected, the __________________ the offset will be, but the ______ the tendency of the control loop to oscillate.
    • A. 

      Larger, smaller

    • B. 

      Smaller, greater

  • 23. 
    True or false: the P-controller is load-independent and the I-controller is load-dependent.
    • A. 

      True

    • B. 

      False

  • 24. 
    A two-position controller would be a good choice for all but which of the following applications?
    • A. 

      As a hygrostat to switch the humidifier of a room humidity control system

    • B. 

      As a pressostat to switch the compressor of a compressed air station

    • C. 

      As a flow temperature low-limit controller in a floor heating system

    • D. 

      As a temperature controller for a domestic hot water heater

    • E. 

      As a frost protection thermostat in a ventilation system

  • 25. 
    A generally applied rule of thumb recommends that the loop gain Vo should be set to __________ of the critical loop gain.
    • A. 

      One-fourth

    • B. 

      Half

    • C. 

      Three-fourths

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