Building Automation Systems

Question 1

__ __ control system utilizes an actuating device to control the process directly without asking for feedback

Answer 1

open loop

Question 2

__ __ control system utilizes feedback to compare the measured variable to the desired result

Answer 2

Closed Loop

Question 3

Refers to data received by the controller

Answer 3

input

Question 4

refers to data received by the controller

Answer 4

output

Question 5

a continuous signal that varies through a range of values. proportional

Answer 5

analog

Question 6

a time-separated signal that carries information in binary form. only two state of positions; on or off. yes or no. open of closed.

Answer 6

digital

Question 7

value of the controlled variable that is to be maintained

Answer 7

set point

Question 8

actual measured value of the controlled variable

Answer 8

measured value

Question 9

the difference between the set point and the actual value of the controlled variable

Answer 9

error

Question 10

two position controller, it is the difference between the settting at which the controller operates at one position and the setting at which it changes to the other position.

Answer 10

differential

Question 11

a type of controller for which the output can vary infinitely over the range of the controller

Answer 11

modulating controller

Question 12

a controller for which an increase in the level of the sensor signal vs a controller for which an increase in the level of the sensor signal results in a decrease in the level of the controller output.

Answer 12

direct acting controller vs reverse acting controller

Question 13

minimize pressure drop across valve

Answer 13

control valve sizing and pressure drop

Question 14

excessive pressure drop could be

Answer 14

poor selection (high Cv factor)
Valve and/or actuator impaired

Question 15

the number of US gallons of water per minute at 60 degrees that will flow through a valve with a pressure drop of one psi

Flow (GPM) = Cv * square root of change in pressure (PSI)

Answer 15

flow coefficient

Question 16

Proportional control is __ and the corrective action often __ the target

After arriving at the set point, there will be no controller action and you can get __ target.

proportional to size of error

Answer 16

reactive, overshoots, off

Question 17

Proportional, integral, and derivative are __ __ systems that use a feedback signal to control a certain actual

Answer 17

closed loop

Question 18

Integral Control increases corrective action in relation not only to the error but also to the….
Integral control corrective action if results aren’t achieved as time passes

Answer 18

time it has persisted

Question 19

Proportional + Integral control can __ the time to get to steady state

Answer 19

reduce

Question 20

With derivative control, if sudden changes occur, the response will be related to the __ __ __

derivative control is useful when trying to stay __ __ in a precisely controlled system

Answer 20

rate of change

on target

Question 21

__ control systems are operated by clean, dry, and oil free compressed air flow at low pressure.

includes: receiver controller, actuator and valve, damper actuator

safe and easy to operate, reliable in harsh environments
not very precise, sensitive to vibrations

Answer 21

pneumatic

Question 22

__ control is a process that transforms one or more input signals into different output signals so as to give the desired system response

instantaneous, very little affected by normal temps
very accurate
different manufactures used different signals so inoperable

Answer 22

Electrical

Question 23

__ __ controller received input from the sensor and then sens output signals in ‘packets’ using digital communication

Different _ _ _ can be networked together using a data bus

Answer 23

Direct Digital Control

Question 24

ASHRAE 135

Answer 24

BACnet - Building Automation and Control Networking protocol

Question 25

A __ typically runs HVAC systems A __ automates the functions of a __ system and enables savings via lighting, metering, access control, and other systems A __ system is a subset of the __ the __ will allow you to visualize and manage your building systems in such a way that you can create energy savings

Answer 25

control system building automation system control system

Question 26

What is an advantage of a hot water reset?

Answer 26

Maintain lowest hot water supply temp that will meet needs | reduces load on the boiler as well as thermal lasses throughout the distribution

Question 27

What is an advantage of a chilled water reset

Answer 27

Raises the temperature set point of water leaving the chiller Most chilled water setting are designed with the heaviest anticipated cooling load significant cost savings can result from resetting chilled water temps. in anticipation of cooling load

Question 28

Before a static pressure reset, all of the VAV boxes partially open creating static pressure in the main duct, typically around 2 inches. This results in ___ fan horsepower maintaining this __ than necessary set point. After the static pressure reset, the DDC system monitors the VAV static pressure and lowest the pressure until only __ damper is completely ___, which is a better means of determining minimum flow requirements.

Answer 28

wasted, higher one, open

Question 29

An economizer __ cooling energy by optimizing mixed air temperature as the outside air allows, the outdoor air damper open __

Answer 29

reduces, more

Question 30

A room temperature sensor supplying information/feedback to an HVAC system is an example of: __ input, __ outpout

Answer 30

Analog Input, Closed Loop output

Question 31

An actuator mounted on a variable air volume box would be a decide that would receive an __ output signal

Answer 31

Output

Question 32

Which approach is most likely to provide the greatest improvement in boiler combustion efficiency (assuming no change in fuel) 1. Increase stack temp and increase combustion air temp 2. Fix all steam leaks 3. Reduce stack temp and decrease combustion air temp 4. Increase boiler excess oxygen and increase stack temp 5. Reduce boiler excess air and reduce stack temp.

Question 33

Reducing excess air in boiler __ the oxygen in the stack and for better combustion efficiency

Answer 33

reduces

Question 34

Reducing the stack temperature by installing an economizer or combustion air pre-heater ___ the stack temperature rise and further improves efficiency

Answer 34

reduces