HVAC Flashcards
An Enthlapy economizer is an economizer that uses temperature and humidity levels of the outside air to control its operation.
True
Chillers include metering devices, evaporators, condensers, and compressors that are similar to direct expansion refrigeration systems.
True
Cooling towers are categorized as either forced-draft or induced draft.
True
Commercial air heat pumps are commonly water-to-air heat pumps.
True
A _____ compressor is a compressor that uses one or more pistons that reciprocate inside closed cylinders to compress refrigerant vapor.
Reciprocating
A ___ air-handling unit is an air-handling unit that moves a constant volume of air.
Constant-volume
A ___ is a device that controls the airflow to a building, matching the building space requirements for comfort.
Variable-air (VAV) terminal box
A ___ air-handling unit is an air-handling unit that delivers air at a constant 55°F temperature to building spaces.
Terminal reheat
A ___ is an electronic device that controls the direction, speed, and torque of an electric motor.
VSD or VFD.
A controller is a device that receives a signal from a sensor, compares it to a setpoint value, and sends an appropriate output signal to a controlled device.
True
Closed Loop control is in which feedback occurs between the controller, sensor, and controlled device.
True
The most common method of humidity control return air control is a humidity sensor or controller in the building space.
True
___ is the measurement of the results of a controller action by a sensor and a switch.
Feedback
In ___ control systems, transducers are used as an interface between different control systems technologies.
hybrid
An ___ control system is a control system that uses a variable signal.
analog
Humidity sensors drift over time, with inaccuracies of ___% per year being common.
1
The ___ of the actuator is the length of time that it takes the actuator to move from one extreme to the other.
Stroke time
An ___ is a device that produces a continuous signal between two values.
Analog output
A ___ is a solid-state switching device used to switch alternating current.
triac
Differential pressure switches are often used to indicate ___
Air handling unit filter condition
____ temperature sensors are the most common temperature sensors used in building automation systems and are used to sense air temperatures in building spaces.
Wall mount
The most common humidity sensors measure percent relative humidity (%rh), while other sensors measure dew point or absolute humidity.
True
An ___ is a device that senses a variable such as temperature, pressure, or humidity and causes a proportional electrical signal change at the building automation controller.
Analog input
A temperature
