ASHRAE ASHRAE Controls Automation and Building Systems Integration

Question 1

What communication protocol is widely recognized by ASHRAE as the standard for building automation and control network (BACnet) interoperability?

Accepted Answer

BACnet (ASHRAE Standard 135)

Answer

Modbus RTU only

Answer

LonWorks only

Answer

DALI (Digital Addressable Lighting Interface)

Question 2

In ASHRAE building control terminology, what is a 'setpoint' in a control loop?

Accepted Answer

The desired target value that the controller attempts to maintain for a controlled variable

Answer

The maximum allowable pressure in a refrigerant circuit

Answer

The minimum outdoor air fraction required for ventilation

Answer

The rated capacity of the HVAC equipment at design conditions

Question 3

What type of control action does a proportional-integral-derivative (PID) controller use to eliminate steady-state offset in HVAC systems?

Accepted Answer

Integral action

Answer

Proportional action

Answer

Derivative action

Answer

On-off (bang-bang) action

Question 4

According to ASHRAE guidelines, what is 'economizer control' in an air-handling unit?

Accepted Answer

A control strategy that uses outdoor air for free cooling when outdoor conditions are favorable, reducing mechanical cooling energy

Answer

A method to reduce fan speed during low-load periods to save fan energy

Answer

A sequence that pre-heats outdoor air in cold climates to prevent freezing of coils

Answer

A control mode that cycles the compressor to maintain supply air temperature within a dead band

Question 5

In ASHRAE Variable Air Volume (VAV) system controls, what is the primary variable that the VAV terminal unit modulates?

Accepted Answer

Airflow rate to the zone

Answer

Supply air temperature at the AHU

Answer

Chilled water flow through the cooling coil

Answer

Static pressure in the main supply duct

Question 6

What does ASHRAE define as a 'direct digital control (DDC)' system in building automation?

Accepted Answer

A control system where a digital computer or microprocessor directly performs the control algorithm and sends output signals to controlled devices

Answer

An analog pneumatic control system with digital display readouts

Answer

A system where building operators manually enter setpoints via a digital touchscreen

Answer

A control network that transmits analog 4-20 mA signals between field devices