What's a vfd? How does it functions? What's difference in vrf and vav system? Which nfpa code used for fire pumps? What's a freeboard in tanks?

Question

Accepted Answer

A VFD is a Variable Frequency Drive used to control the speed of an electric motor. VRF and VAV systems are different types of HVAC systems. NFPA 20 is the code used for fire pumps. Freeboard is the distance between the liquid level and the top of a tank.

VFD stands for Variable Frequency Drive.
It is used to control the speed of an electric motor by varying the frequency and voltage supplied to the motor.
VFDs are commonly used in industrial applications to save energy and provide precise control over motor speed.
VRF (Variable Refrigerant Flow) and VAV (Variable Air Volume) are both types of HVAC systems.
VRF systems use refrigerant to transfer heat between indoor units and outdoor units, providing individual temperature control in different zones.
VAV systems control the airflow to different zones by varying the volume of air supplied.
NFPA 20 is the National Fire Protection Association code that provides guidelines for the installation and operation of fire pumps.
Freeboard in tanks refers to the vertical distance between the liquid level and the top of the tank.
It is important to have sufficient freeboard to prevent overflow and accommodate any potential expansion of the liquid.