Book 2 Chapter 11: Electric Controls For Heating Systems Flashcards
A controller is a device that reacts to which of the following to provide two-position, floating, or proportioning control of an actuator or relay?
A) Pressure
B) Temperature
C) Humidity
D) All of the above
D) All of the above
A room thermostat should be mounted on an inside wall about _________ above the floor and in the path of natural air circulation when the heating system is off.
A) 4.5m (15ft)
B) 1.5m (5ft)
C) 2.5m (8ft)
D) 3.5m (11.5ft)
B) 1.5m (5ft)
A capacitor type control motor has the rotor and gear train sealed in a housing partially filled with:
A) Water
B) Glycol
C) Oil
D) Grease
C) Oil
The electric current is transmitted through an electric wire, called the __________ to the burner.
A) Connecting link
B) Positive loop
C) Negative loop
D) Neutral
A) Connecting link
Which of the following types of switching devices are used in conjunction with bimetal strips to control high voltage circuits?
A) Open-contact switch
B) Thermostatic switch
C) Bimetal switch
D) Mercury bulb switch
D) Mercury bulb switch
The bimetal sensing element consists of a strip made up of two thin layers of metal with:
A) Widely different rates of thermal expansion
B) Widely different rates of thermal conductivity
C) Slightly different rates of thermal expansion
D) Similar rates of thermal expansion
E) Slightly different rates of thermal conductivity
A) Widely different rates of thermal expansion
Using electricity for control purposes has the following advantages:
1. It is readily available
2. The wiring is usually simple and easy to install
3. Signals from sensing elements can only produce one output
4. Controller/actuators do not require an air supply
A) 1,2,4
B) 1,2,3
C) 1,3,4
D) 2,3,4
E) 1,2,3,4
A) 1,2,4
A transformer is a device that is used to change:
A) AC voltage from one value to another
B) Both AC and DC voltages
C) AC amperage from one value to another
D) DC amperage from one value to another
E) DC voltage from one value to another
A) AC voltage from one value to another
In a basic electrical control system, the device that senses a drop in air temperature is called the:
A) Final controlled device
B) Thermostat
C) Humidistat
D) Regulator
E) Pneumatic temperature sensor
B) Thermostat
On-off thermostats are equipped with a/an:
A) Open contact switch
B) High temperature switch
C) High voltage switch
D) Low voltage switch
E) Low temperature switch
A) Open contact switch
When a temperature below set point is sensed, the thermostat:
A) Operates a switch
B) Opens to send an electrical signal
C) Controls a transformer
D) Closes to send an electric signal
E) Starts the fan
D) Closes to send an electric signal
An example of a heating system controlled device would be:
A) Thermostat
B) Hot water boiler
C) Radiator
D) Damper motor
E) Steam boiler
D) Damper motor
Thermostats may be classified according to their:
A) Type of control action provided
B) Application
C) Type of temperature sensing element
D) Temperature range
E) All of the above
E) All of the above
A valve that can be used for either mixing or diverting service is:
A) Float valve
B) Radiator valve
C) Three way vale
D) Fuel valve
E) Check valve
C) Three way valve
The sensing element of a bimetal thermostat consists of a:
A) Hygroscopic element
B) Bourdon tube
C) Strip made up of two thin layers of different metals which expand at widely different rates
D) Diaphragm with sensing pressure on one side and a reference pressure on the other
E) Bulb/capillary tube/bellows combination containing a volatile liquid
C) Strip made up of two thin layers off different metals which expand at widely different rates
When dealing with controls a control valve is a device:
A) That connects an actuator to a damper or control valve
B) Used to change AC voltage from one value to another
C) Used to control the flow of air in a duct or through a wall louvre
D) Used to position dampers and control valves
E) Used to control the flow of fluid of gas such as water,air, or steam
E) Used to control the flow of fluid of gas such as water, air, or steam
When dealing with electrical controls line voltage refers to:
A) The electric switch configuration of a relay
B) A term that refers to the normal electric supply voltage
C) A term that refers to wiring or other electrical devices using 30 volts or less
D) A device consisting of a Selonoid coil, which operates load carrying contacts when the coil is energized
E) A device used to change AC voltage from one value to another
B) A term that refers to the normal electric supply voltage
The electrically operated radiator valve is a ________ valve is used for two position (on-off) control of steam or hot water to radiators, convectors, etc.
A) Ball
B) Double seated
C) Gate
D) Single seated
E) Butterfly
D) Single seated
A three way valve is a:
A) Double-seated valve
B) Gate-seated valve
C) Triple-seated valve
D) Ball-seated valve
E) Single-seated valve
A) Double-seated valve
Electrical control system usually employ a normal line voltage of:
A) 12 or 24 volts AC
B) 240 or 600 volts AC
C) 120 or 240 volts AC
D) 12 or 24 volts DC
E) 120 or 240 volts DC
C) 120 or 240 volts AC
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 position dampers and control valves
C) Used to control the flow of fluid or gas such as water, air, or steam
D) Used to change AC voltage from one value to another
E) That connects an actuator to a damper or control valve
B) Used to position dampers and control valves
Electrical contacts that complete electric circuits when a relay is de-energized are referred to as _________ contacts.
A) Normally closed (NC)
B) Naturally closed (NC)
C) Not open (NO)
D) Naturally open (NO)
E) Normally open (NO)
A) Normally closed (NC)
One of the most important controls in a heating system is the:
A) Humidistat
B) Aquastat
C) Operating control
D) Thermostat
E) Pressurestat
D) Thermostat
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) Immersion thermostat or Aquastat
C) Remote bulb thermostat
D) Pressurestat
E) Bimetal thermostat
B) Immersion thermostat or Aquastat
