Question 1

The proper documentation of control systems is essential if they are to be expediently serviced in the future.A universally accepted tool for such documentation is the ____.

Accepted Answer

Ladder diagrams are universally accepted tools for documenting control systems, especially in the context of electrical engineering and automation. They provide a clear and straightforward way to represent the control logic of systems, making them easier to understand and service in the future.

Question 2

There are hydronic heating applications where control action is required based on the difference between two temperatures rather than the value of either temperature.

Accepted Answer

This is true. Some examples of such applications include outdoor reset control and delta-T circulators.

Question 3

The term ____ differential refers to the actual variation in the controlled variable as the system operates.

Accepted Answer

The term "operating differential" refers to the actual variation in the controlled variable as the system operates, indicating the range within which the system adjusts to maintain the desired setpoint.

Question 4

One purpose of mixing is to protect conventional boilers from operating at conditions that allow sustained flue gas condensation.

Accepted Answer

Mixing helps raise the temperature of the flue gas before it enters the boiler, preventing sustained flue gas condensation which can damage the boiler.

Question 5

For current-generation hydronic heating systems, the controlled variable is usually indoor air temperature.

Accepted Answer

In hydronic heating systems, the most common controlled variable is indoor air temperature, which is typically maintained by adjusting the flow rate of hot water circulating through the radiators or other heating elements.

Question 6

The combination of near-continuous circulation and very gradual changes in water temperature tends to maximize expansion noises from the distribution piping and heat emitters.

Accepted Answer

The combination of near-continuous circulation and very gradual changes in water temperature tends to minimize expansion noises from the distribution piping and heat emitters, as it avoids sudden temperature changes that cause rapid expansion or contraction.

Question 7

As outdoor temperature increases, and the heating load decreases, the water temperature supplied to the heat emitters also decreases as does their heat output.This concept is called outdoor ____ control.

Accepted Answer

This concept is called outdoor reset control, where the supply water temperature is adjusted based on the outdoor temperature. As the outdoor temperature increases, the heating load decreases, and the water temperature supplied to the heat emitters also decreases to maintain a comfortable indoor temperature without wasting energy. This helps in reducing energy consumption and improving efficiency.

Question 8

Most of the closed-loop control systems used for hydronic heating continually seek to eliminate any error that exists between the target value and measured value of the controlled variable.

Accepted Answer

Closed-loop control systems are designed to minimize or eliminate any error that exists between the target value and the measured value of the controlled variable. This is usually achieved by adjusting the control output based on feedback from sensors that measure the current state of the system.

Question 9

In addition to equal run time rotation, there are other operating options available for staged/modulating heat sources.They are called series staging/modulation, parallel staging/modulation, and ____ staging/modulation.

Accepted Answer

Hybrid staging/modulation is another operating option for staged/modulating heat sources, combining different methods to optimize performance and efficiency.

Question 10

The term injection mixing applies to any mixing assembly in which ____ is pushed (e.g., injected) into a circulating distribution system.

Accepted Answer

Injection mixing refers to the process where hot water is injected into a circulating distribution system to achieve the desired temperature or mixing effect.

Question 11

A network control system without Internet access requires a person to be present to interrogate or adjust the system.This is unnecessary with a(n) ____ networked control system.

Accepted Answer

A web-enabled networked control system can be accessed remotely through the internet, eliminating the need for physical presence to interrogate or adjust the system.

Question 12

Most heat source reset controllers have an adjustable minimum supply temperature.

Accepted Answer

Most heat source reset controllers have an adjustable minimum supply temperature, allowing for customization of the system to meet specific needs and preferences. This feature helps ensure optimal performance and energy efficiency.

Question 13

Direct injection mixing, whether accomplished using a two-way valve or variable-speed pump as the injection control device, provides the highest temperature difference between the supply and return injection risers.

Accepted Answer

Direct injection mixing can achieve a higher temperature difference between supply and return injection risers compared to other mixing methods, such as recirculation mixing. This is because the injection control device (two-way valve or variable-speed pump) allows for more precise control of the amount of hot and cold water being mixed together.

Question 14

To provide accurate control under low-load conditions, the controlled device must be able to maintain stable flow at very low flow rates.Such a device is said to have good ____.

Accepted Answer

Rangeability refers to the ability of a control valve to maintain accurate control over a wide range of flow rates. A high rangeability means the valve can provide accurate control even at very low flow rates, making it suitable for low-load conditions.

Question 15

A multizone relay center is designed to isolate the wiring and control operation of several independent zone circulators or zone valves.

Accepted Answer

The answer of A multizone relay center is designed to...

Question 16

Boiler protection is accomplished by ____ the rate of heat flow from the boiler into the distribution system whenever the boiler temperature approaches or falls below a specified minimum operating temperature.

Accepted Answer

To protect the boiler from damage due to low temperatures, the rate of heat flow from the boiler into the distribution system needs to be reduced. This can be achieved through various methods such as reducing the firing rate, increasing the boiler water temperature, or using a bypass valve to divert water away from the distribution system. This helps to prevent the water in the boiler from cooling too much and potentially causing damage to the system.

Question 17

Heat output from the heat emitter occurs whenever the supply water temperature equals the room air temperature.

Accepted Answer

Heat output from the heat emitter occurs when the supply water temperature is higher than the room air temperature, allowing heat transfer from the emitter into the room.

Question 18

Relay contacts are designated as normally open, or normally closed.In this context, the word "normally" means when the coil of the relay is not energized.

Accepted Answer

The term "normally" in the context of relay contacts refers to the state of the contacts when the relay coil is not energized. Normally open contacts are open in this state, while normally closed contacts are closed.

Question 19

____ control is a planned strategy for shedding (e.g., temporarily turning off) one or more loads when a specific condition is detected in the system.

Accepted Answer

Priority control involves shedding loads based on a predetermined hierarchy or priority when specific conditions are detected in the system.

Question 20

Switches and relays are classified according to their poles and throws.The number of ____ is the number of independent and simultaneous electrical paths through the switch.

Accepted Answer

The number of poles in a switch determines the number of independent and simultaneous electrical paths through the switch.

Quiz 9: Control Strategies, Components, and Systems