Hydronic System Basics

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Key Questions

The following key questions are answered in this module:

What is hydronics?
Hydronics is a means of heating and cooling using a fluid as the heat transfer medium.

What is the difference between an open system and closed system?
An open system has some point in the system open to the atmosphere, while a closed system is not open to the atmosphere at any point; the fluid is never exposed to anything outside of the system itself.

What is the First Law of Thermodynamics?
The First Law states that energy cannot be created or destroyed; it can only be transferred or changed in form

What is the Second Law of Thermodynamics?
The Second Law says that as energy is transformed and transferred, more and more of it is wasted as heat.

What is a pump?
A pump is a device that moves fluids using mechanical action.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

It's a safe bet that you already know what a pump is and what it does. But what you may not know is that numerous pump types move fluids, and their construction and operation are dictated by the type of fluid they are moving. The root definition for a pump is simply a device that moves fluids using mechanical action. There are two types of pumps: positive displacement and rotodynamic. Positive displacement pumps “grab and go," as a fixed amount of fluid captured by a rotor, gear, piston, or some other device that creates a void at the pump inlet. It is then mechanically moved (displaced) to the pump discharge. Displacement pumps provide a constant flow at a given speed regardless of the pressure in the system. An example of these basic pumps are the oil and water pumps in your car’s engine. While positive displacement pumps are easy to understand, rotodynamic pumps are a bit less intuitive. Rotodynamic pumps “throw and go” by transferring kinetic energy to the water via rotation. The fluid is thrown within the pump, and in turn, kinetic energy transfers to the fluid as its velocity increases. As the pump discharges, the velocity reduces, and the energy converts to potential energy in the form of increased pressure. Note that centrifugal pumps do not “suck” water in. They create conditions where the pressure of the system at the pump inlet (the suction head), pushes the water into the pump. Specifically, as the fluid leaves the pump, system pressure at the pump inlet pushes fluid into the void left behind the discharged fluid. There are numerous types of rotodynamic pumps, but the most common in commercial buildings are the centrifugal type.