Chapter 11 Electric Controls for Heating Systems Flashcards
1.Three-way valves can be used in hydronic heating systems for \_\_\_\_\_ service. A. Mixing B. Pressure C. Volume D. Agitating E. Coagulating
A. Mixing
2. The sensing element of the \_\_\_\_\_ is liquid filled and the switch is actuated by the expansion and contraction of the liquid when there is a temperature change of the controlled medium. A. Humidistat B. Pressurestat C. Bimetal thermostat D. Immersion thermostat or Aquastat E. Remote bulb thermostat
D. Immersion thermostat or Aquastat
- When dealing with controls an actuator is a device:
A. Used to control the flow of air in a duct or through a wall louvre
B. Used to control the flow of fluid or gas such as water, air, or steam
C. That connects an actuator to a damper or control valve
D. Used to position dampers and control valves
E. Used to change AC voltage from one value to another
D. Used to position dampers and control valves
- When dealing with controls a damper is a device:
A. Used to control the flow of fluid or gas such as water, air, or steam
B. Used to control the flow of air in a duct or through a wall louvre
C. That connects an actuator to a damper or control valve
D. Used to position dampers and control valves
E. Used to change AC voltage from one value to another
B. Used to control the flow of air in a duct or through a wall louvre
5. In a typical electric control system the electric current is transmitted through a wire called the \_\_\_\_\_ to the burner. A. Neutral line B. Positive loop C. Negative loop D. Control link E. Connecting link
E. Connecting link
- The sensing element of a remote bulb thermostat consists of a:
A. Diaphragm with sensing pressure on one side and a reference pressure on the other
B. Hygroscopic element
C. Bulb/capillary tube/bellows combination containing a volatile liquid
D. Bourdon tube
E. Strip made up of two thin layers of different metals which expand at widely different rates
C. Bulb/capillary tube/bellows combination containing a volatile liquid
- When dealing with controls a controller is a device:
A. Which reacts to pressure, temperature, or humidity to provide two position, floating, or proportioning control of an actuator or relay
B. Used to change AC voltage from one value to another
C. That connects an actuator to a damper or control valve
D. Used to position dampers and control valves
E. Used to control the flow of fluid or gas such as water, air, or steam
A. Which reacts to pressure, temperature, or humidity to provide two position, floating, or proportioning control of an actuator or relay
8. A room thermostat should be mounted on an inside about \_\_\_\_\_ above the floor and in the wall about path of natural air circulation when the heating system is off. A. 4.5 m (180 in) B. 1.5 m (60 in) C. 2.5 m (100 in) D. 3.5 m (140 in) E. 4.0 m (157 in)
B. 1.5 m (60 in)
9. One of the most important controls in a heating system is the: A. Pressurestat B. Aquastat C. Operating control D. Thermostat E. Humidistat
D. Thermostat
- When dealing with electrical controls line voltage refers to:
A. A term that refers to wiring or other electrical devices using 30 volts or less
B. A device used to change AC voltage from one value to another
C. A term that refers to the normal electric supply voltage
D. A device consisting of a solenoid coil, which operates load carrying contacts when the coil is energized
E. The electric switch configuration of a relay
C. A term that refers to the normal electric supply voltage
- The electric modulating thermostat uses a _____ to produce a varying output signal.
A. Variable potentiometer B. Sensing bulb C. Bimetal strip D. Bourdon tube E. Bellows
A. Variable potentiometer
12. Electrical contacts that complete electric circuits when a relay is de-energized are referred to as \_\_\_\_\_ contacts. A. Naturally open (NO) B. Normally open (NO) C. Normally closed (NC) D. Naturally Closed (NC) E. Not open (NO)
C. Normally closed (NC)
13. A three-way valve is a: A. Gate-seated valve B. Ball-seated valve C. Triple-seated valve D. Single-seated valve E. Double-seated valve
E. Double-seated valve
- Using electricity for control purposes has the following advantages except:
A. It is readily available.
B. The wiring is usually simple and easy to install.
C. A source of compressed air is required
D. The signals received from sensing elements can be used to produce more than one electro-mechanical output.
E. Single controller/actuator combinations are possible
C. A source of compressed air is required
15. The duct thermostat is used to sense the air temperatures in: A. Rooms B. Coolers C. Freezers D. Boilers E. Ducts and plenums
E. Ducts and plenums
16. In a typical electric control system in a warm air heating system the thermostat is referred to as the: A. Set point B. Controlled variable C. Manipulated variable D. Controller E. Final control element
D. Controller
17. Electrical control systems usually employ a normal line voltage of: A. 120 or 240 volts AC B. 120 or 240 volts DC C. 12 or 24 volts AC D. 12 or 24 volts DC E. 240 or 600 volts AC
A. 120 or 240 volts AC
- When dealing with controls a control valve is a device:
A. Used to control the flow of air in a duct or through a wall louvre
B. Used to change AC voltage from one value to another
C. That connects an actuator to a damper or control valve
D. Used to position dampers and control valves
E. Used to control the flow of fluid or gas such as water, air, or steam
E. Used to control the flow of fluid or gas such as water, air, or steam
- The motor operator used with a motor-operated valve consists of a:
A. Reversible driving motor and reduction gears mounted in a sealed casing and completely submerged in water
B. Direct driving motor and reduction gears mounted in a sealed casing and completely submerged in oil
C. Direct driving motor and reduction gears mounted in a sealed casing and completely submerged in water
D. Reversible driving motor and reduction gears mounted in a sealed casing and completely submerged in oil
E. Reversible driving motor and reduction gears mounted in an open casing and completely submerged in oil
C. Direct driving motor and reduction gears mounted in a sealed casing and completely submerged in water
- Electrical control systems may use a low voltage of:
A. 12 or 24 volts DC B. 12 or 24 volts AC C. 120 or 240 volts DC D. 122 or 240 volts AC E. 240 or 600 volts DC
A. 12 or 24 volts DC
- The sensing element of a bimetal thermostat consists of a:
A. Bulb/capillary tube/bellows combination containing a volatile liquid
B. Hygroscopic element
C. Diaphragm with sensing pressure on one side and a reference pressure on the other
D. Bourdon tube
E. Strip made up of two thin layers of different metals which expand at widely different rates
E. Strip made up of two thin layers of different metals which expand at widely different rates
