The rectifier in the VSD system converts the AC power to DC power. The DC power is then used to power an inverter, which converts the DC power back to AC power at a variable frequency for controlling the speed of the motor

A motor contactor is an electrical switch that is used to control the starting and stopping of an electric motor.

Specific volume is the volume occupied by one unit mass of a substance. In the case of air, specific volume is expressed in cubic feet per pound of dry air.

Because they can weaken the duct and create a potential for leaks. Instead, duckboard sections should be joined using a tongue-and-groove joint or a lap joint.

An expansion valve (Thermostatic expansion valves (TXVs)) is used to control the flow of refrigerant in an air conditioning or refrigeration system.

A power factor correction (PFC) capacitor is used to increase the power factor of a circuit. A power factor is a measure of how efficiently electrical energy is used.

The LRA is the current that the motor draws when the rotor is not rotating. This occurs when the motor is first started, or when there is a heavy load on the motor. In order to reduce starting current, different methods of starting are employed.

Speed = (120 x frequency) (1-slip) / poles of the motor
= (120 x 60) (1 – 0.02 ) / 4            (Slip is assumed 2% and its varying quantity)
= 1764 RPM

An ampere is the measurement of electric current. Electric current is the flow of electric charge through a conductor.

The wet bulb depression is the difference between the dry bulb temperature and the wet bulb temperature. When the moisture present in the air increases, the wet bulb temperature will be higher. Therefore wet-bulb depression decreases.

A suction line accumulator is used to prevent liquid refrigerant from entering the compressor. It is a small tank that is installed in the suction line, which is the line that carries the refrigerant from the evaporator to the compressor.

During defrost mode, the heat pump switches from heating mode to cooling mode. This is done to melt the frost that has accumulated on the evaporator coil. The compressor is not used during defrost mode because it would only serve to refreeze the evaporator coil.

with a more heating surface, more heat can be transferred from the fire to the water or steam. This can be achieved by increasing the surface area of each tube, increasing the number of tubes or using a finned tube

Low-pressure steam boilers are typically used in residential and commercial applications where the need for high-pressure steam is not required.