What is a Control in an HVAC system?
A control, or controller, in an HVAC system regulates the temperature by opening and closing the circuit to the heating or cooling system. The control may be mechanical, electrical, or electronic. A typical home thermostat is an example of a control. The control might also be part of the heating or cooling system itself, such as a furnace damper or air conditioner blower motor.
In a typical home, the control is located on a wall inside the house. It consists of a series of sensors and relays that monitor and control the functions of the heating and cooling system. The sensors may be simple mechanical devices, such as a bimetallic strip that expands or contracts with changes in temperature, or they may be electronic devices, such as thermocouples or resistance temperature detectors (RTDs).
The relays in the control system activate the various components of the heating and cooling system. For example, when the temperature in the house drops below the set point, the relay will close the circuit to the furnace, causing it to turn on. When the temperature in the house rises above the set point, the relay will open the circuit to the furnace, causing it to turn off.
Control systems for HVAC systems can be either manual or automatic. Manual controls are operated by the user, such as a switch that turns the furnace on and off. Automatic controls use sensors and relays to monitor and maintain the desired temperature without user intervention.
Programmable controls allow you to program different levels of comfort for different times of the day. For example, you can set the thermostat to a lower temperature when you are asleep or away from home, and a higher temperature when you are awake and at home. Programmable controls can save you money on your energy bill by reducing the amount of time the heating and cooling system is running.
HVAC Control Methods -A review