B-4 Hydronic Heating Piping and Components Introduction

The following terms will be used throughout this section. A complete list of terms for this section can be found in the Glossary.

• air purger: (Also called air separators or air scoops); A device used in heating and cooling systems to remove larger air pockets and air bubbles from water, which can cause problems like noisy pipes or reduced efficiency. The device helps to keep the system running smoothly by ensuring that the water is free from air. Also see microbubble resorber. (Section B-4.1)
• backflow preventer: A device that stops water from flowing backward into the water supply. It ensures that water doesn’t get contaminated by preventing dirty or used water from flowing back into clean water lines.  (Section B-4.2)
• balancing valve: A valve used in a piping system to control and balance the flow of fluid to ensure that each part of the system gets the right amount of flow. It also helps to make sure that all sections of the system work efficiently and evenly. (Section B-4.3)
• ball valve: A valve that controls the flow of liquid using a ball with a hole through the center. When the ball is turned so that the hole lines up with the pipe, liquid flows through. When the ball is turned so that the hole is perpendicular to the pipe, the flow is blocked. Ball valves are known for their quick and easy on-off operation. (Section B-4.1)
  
• bypass valve (quick fill valve): A valve that allows water to quickly flow around a system or component. It is used to quickly fill up or bypass parts of the system, making it easier to manage and maintain. (Section B-4.2)
• cavitation: The process where tiny bubbles or vapor pockets form in a liquid when the pressure drops below the liquid’s vapor pressure. These bubbles can collapse suddenly, creating strong shock waves and high temperatures. Cavitation can occur in pumps, propellers, and other machinery. While it can be useful in some processes (like cleaning or mixing), it can also cause damage to equipment over time. (Section B-4.1)
• centrifugal pump: A device that moves liquids by using a rotating impeller. The impeller spins the liquid outward through centrifugal force, pushing it through the pump and into the pipes of a system. Centrifugal pumps are commonly used in water supply, heating, and cooling systems to efficiently move fluids. (Section B-4.1)
• check valve: A valve that allows liquid to flow in only one direction. It automatically closes when the liquid starts to flow backward, preventing backflow. Check valves are used to keep liquids from flowing the wrong way in a pipe system. (Section B-4; Section B-4.2)
• circulating pump (or circulator): A device that moves water through a heating or cooling system. It helps distribute hot or cold water to different parts of a building, ensuring even temperature control. Circulating pumps are essential for systems like radiators and underfloor heating. (Section B-4; Section B-4.1)
• component isolation: The process of shutting off or separating a specific part of a system, like a pipe or valve, from the rest of the system. This is done to allow for repairs or maintenance without affecting the entire system. It ensures that only the isolated part is affected while the rest continues to operate normally. (Section B-4.2)
• direct return: A piping system design where the water or fluid returns directly to the source or starting point after passing through each section of the system. This means that each section gets the same temperature fluid and helps in balancing the system evenly. (Section B-4.3)
• equalizer line: The vertical piping at the end of the header going back to the boiler return connection. Its job is to return any water that slips out of the boiler with the steam, and to balance the pressure between the supply and the return sides of the boiler. Without a properly sized equalizer, water can back out of the boiler. (Section B-4)
• expansion tank: A special tank in a heating or cooling system that helps manage the pressure caused by changes in temperature. When the water heats up and expands, the expansion tank provides extra space for the water to go, so the system doesn’t get too much pressure. (Section B-4.1)
• feedwater valve: A valve that controls the amount of water that enters a system and lowers the pressure to a safe level. It helps keep the water pressure steady and safe for the system.  (Section B-4.2)
• flow regulation: The control of how much fluid flows through a pipe or system. It involves adjusting valves or other devices to manage the flow rate, pressure, or speed of the fluid. This helps ensure that the system works efficiently and that different parts of the system receive the correct amount of fluid. (Section B-4.2)
• gate valve: A valve that controls the flow of liquid by raising or lowering a gate or barrier inside the valve. When the gate is fully open, the flow of liquid is unimpeded. When the gate is closed, it blocks the flow completely. Gate valves are good for stopping or allowing flow but are not ideal for regulating flow. (Section B-4)
• globe valve: A valve that controls the flow of liquid by moving a disc up and down inside the valve. This movement allows for precise control of the flow rate. Globe valves are often used when it’s important to adjust or regulate the flow of liquid rather than just stopping or allowing it. (Section B-4; Section B-4.2)
• hydronic heating: A system that uses water to heat a building. Water is heated in a boiler and then pumped through pipes to radiators or underfloor tubing. As the hot water moves through these pipes, it releases heat into the rooms, keeping them warm. (Section B-1.4; Section B-2; Section B-4)
• impeller: A rotating part of a pump or other machine that moves fluid by spinning. It has blades that push the fluid outward from the center, creating flow and increasing pressure. Impellers are commonly found in devices like centrifugal pumps and are essential for moving liquids efficiently. (Section B-4; Section B-4.1)
• microbubble resorber: A device used in heating and cooling systems to remove very tiny air bubbles (microbubbles) from water that may not be captured by standard air purgers. By getting rid of the bubbles, the microbubble resorber may more efficiently help the system work better and more quietly. See also air purgers.  (Section B-4.1)
• relief valve: The relief valve protects the boiler against a runaway fire. On space-heating steam boilers, the relief valve is set to pop open and relieve pressure at 15 psi. This is the limit for any low-pressure boiler. (Section B-4.2
• reverse-return: A piping system design where the fluid flows in a way that the return path is the opposite of the supply path. This means that the last section to receive the fluid is the first to return it, helping to balance the system and ensure even heating or cooling throughout. (Section B-4.3)
• series loop: A type of piping arrangement where the water or other fluid flows through one section of the system, then directly into the next section, like a chain. In a series loop, all the sections are connected in a single path, so the fluid passes through each one in order. (Section B-4.2)
• thermosiphoning: A process where a liquid moves naturally without the need for a pump, because of temperature differences. When a liquid gets heated, it becomes less dense and rises. Cooler, denser liquid then moves in to take its place. This creates a natural circulation of the liquid. It’s often used in heating systems and solar water heaters. (Section B-4.3)
• venturi: A device that controls the flow of fluid through a pipe by narrowing the pipe at a certain point. This narrowing causes the fluid to speed up and the pressure to drop. Venturis are often used to measure flow rates or to mix fluids. (Section B-4.3)
• zone valve: A valve used in heating or cooling systems to control the flow of fluid to different areas or zones of a building. It allows you to control the temperature in each zone separately, so you can heat or cool only the areas that need it. (Section B-4.4)