HVAC Controls and Thermostats 2

Question 1

What communication protocol, standardized by ASHRAE, was specifically designed for building automation systems?

Accepted Answer

BACnet

Answer

BACnet (Building Automation and Control Networks) is the ASHRAE standard 135 communication protocol designed specifically for HVAC and building automation interoperability.

Question 2

What does PID stand for in HVAC control systems?

Accepted Answer

Proportional-Integral-Derivative

Answer

PID control combines Proportional, Integral, and Derivative actions to minimize error, eliminate steady-state offset, and dampen rapid oscillations.

Question 3

What is the primary function of an economizer in an HVAC control system?

Accepted Answer

To use outdoor air for free cooling when outdoor conditions are favorable

Answer

An economizer uses outdoor air for cooling when outdoor temperature and/or enthalpy is suitable, reducing or eliminating mechanical cooling energy consumption.

Question 4

In a zone control system, what device modulates airflow to individual zones based on each zone's thermostat demand?

Accepted Answer

Zone damper or VAV box

Answer

Zone dampers (in simpler systems) or VAV (Variable Air Volume) boxes modulate airflow to each zone individually based on that zone's thermostat signal.

Question 5

What is 'hunting' in an HVAC control system?

Accepted Answer

Continuous oscillation of the controlled variable above and below setpoint due to overcorrection

Answer

Hunting occurs when a control system repeatedly overcorrects, causing the controlled variable to swing continuously above and below the setpoint without stabilizing.

HVAC Practice Test

HVAC Practice Test

HVAC Controls and Thermostats 2