Principles Of Automatic Heating And Cooling Controls Flashcards
What is meant by the term cold?
Cold is the relative lack of heat
What is the approximate definition of BTU?
British Thermal Unit
- The amount of heat required to raise the temperature of 1 pound of water by 1 degree F.
Heat transfer in an object is always from hot to cold.
True or False?
True
Convection is the way heat is transferred by…
Fluids
Referring to heating/cooling systems, list 4 factors that affect human comfort.
Temperature
Humidity
Air movement
Radiation
In a closed loop system, feedback is optional.
True or False?
False.
A device that reacts to changes in a variable condition is referred to as:
- a relay device
- a controlling device
- an igniting device
- a load device
Controlling device
A limit or safety device detects dangerous conditions in the system.
True or False?
True
A control circuit for a residential heating system is an example of a closed loop control system.
True or False?
True
The heat exchanger:
- contains the heated air that is distributed by the ducts
- is a mechanical device that opens to allow heated air into a room
- is an electrical device that opens a damper to allow heated air into a room
- is a steel enclosure that transfers heat to the air distributed by the ducts
- is a steel enclosure that transfers heat to the air distributed by the ducts
In a domestic gas furnace the fan motor starts when:
- the room thermostat contacts close to call for heat
- the main burner gas valve opens
- the air in the plenum warms up to a preset temperature
- the thermocouple produces sufficient voltage to pull in the relay
- the air in the plenum warms up to a preset temperature
If the plenum gets to hot the high limit device will shut off the fan motor.
True of False?
False
In a properly operating domestic gas furnace the fan motor could keep running after the main burner shuts off.
True of False?
True
A schematic diagram is used to show
- the location of components
- the relative size of components
- the logical operation of components
- the electrical rating of components
- the logical operation of components
If you wanted to find out the relative position of components in a heating system and the wiring between them, you would look at
A wiring diagram
A schematic diagram is drawn with
- Power on and at 20 degrees C
- Power off and no heat
- Power on and no heat
- Power of and at 20 degrees C
- Power off and no heat
An example of a load device is
- A thermostat
- An N.O. contact
- A high limit switch
- A relay coil
- A relay coil
An example of a controlling device is
- a heater
- a pressure switch
- a motor
- Both 1 and 3
- a pressure switch
A gas fired furnace in a single dwelling always needs a properly labeled disconnect switch near the furnace
True or False?
False
Rule 26-806
A residential furnace is allowed to have the light in the furnace room on its supply circuit.
True or False?
False
Rule 26-806
The 24V Class 2 control wiring to the thermostat for residential gas fire heating systems can utilize LVT cable.
True or False?
True
Rule 16-210
Table 19
In a forced air furnace the sensing element for the fan is mounted in the heat exchanger.
True or False?
False
People may feel cold even if the temperature is 20 degrees C
a) False
b) True, if the humidity is to high
c) true if the humidity is to low
d) true if there is insufficient air movement over the body
c) true if the humidity is to low
When control devices in a domestic heating system are connected such that any “1” device could deactivate the main gas valve the devices would be connected in
Series or Parallel?
Series
A forced air system relies on gravity to circulate the warm air.
True or False?
False
Two control devices are connected in series to control one load device. One control device is closed and the other is open.
The load device will be:
a) On
b) Off
c) On or Off depending on something
d) Not working properly
b) Off
A human body can lose heat by radiation if it is to close to a cold wall.
True or False?
True
Low relative humidity can make a room feel colder than it actually is.
True or False?
True
In a forced air gas furnace, the smoke and exhaust gasses are found:
a) inside the heat exchanger
b) in the plenum
c) at the registers
d) in the duct
a) inside the heat exchanger
If the temperature becomes dangerously high in a domestic forced air furnace, which device should safely shut down the heating equipment.
a) the high limit
b) the fan limit
c) auxiliary contact
d) thermocouple
a) the high limit
Rules pertaining to the installation of HVAC systems and equipment are grouped into one section of the code book?
True or False?
False
Convection is a method by which heat is transferred through solids.
True or False?
False
Thermostatically controlled heating systems are considered _______ loop systems
Closed
A heating thermostat symbol on a schematic should be shown
a) N.C. and opens on a rise of temperature
b) N.O. and closed on a drop in temperature
c) N.O. and closes on a rise in temperature
d) None of the above
a) N.C. and opens on a rise of temperature
Controlling devices react to changes in variable conditions such as temperature, pressure or humidity.
True or False?
True
What is meant by the term heat?
Heat is energy in transfer
