A. Bhatia, B.E.

Course Outline

Hydronics is the name for the use of water as the heat-transfer medium in heating and cooling systems. One of the oldest and most often seen instances is steam or hot water radiators. In large-scale commercial buildings such as high-rise and campus facilities, operations may include both chilled and heated water loops to provide for comfort air conditioning needs. Hydronics is complex and good understanding of different hydronic systems is essential for HVAC designer to meet the needs of modern building architecture.

This 3-hr course material is based entirely on US Corps of Engineers Construction Engineering Research Laboratory (USACERL) technical report 99:20, May 1999. This course lists the Appendix E of the report and other appendices have been listed separately.

The course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

Learning Objective

At the conclusion of this course, the student will:

• Understand the basic hydronic system in heating and cooling applications;
• Understand the difference between once through, recirculation, open and closed systems;
• Describe the components of hydronic systems such as air separators, air vents, circulators, relief valves, expansion tanks, flow control devices, miscellaneous valve and fittings;
• Understand water system piping classification for main and branch feeders;
• Learn about the various piping circuits including one pipe, two pipe, three pipe and four pipe systems for various applications;
• Understand different type of heating and cooling terminal units such as unitary equipment, air handling units, baseboard heaters, convectors and radiators;
• Learn different type of hydronic pumps including circulators, closed coupled centrifugal pumps and horizontal split casing pumps;
• Understand different approaches to duct design;
• Understand pump cavitation and pump installation considerations; parallel or series arrangement; and
• Learn basic hydronic system testing, adjusting and balancing (TAB) procedures.
  

Intended Audience

This course is aimed at beginners, novice engineers, building services design engineers, end users, service technicians, architects, maintenance supervisors, contractors, energy auditors, layout professionals and general audience.

Course Introduction

Hydronic heating and cooling is achieved through cold or hot water/steam running through a heat exchanger. Air is then blown over the heat exchanger and then delivered to the desired room. It is important to design and lay the hydronic system components professionally, to ensure that the system operates economically, with minimum energy and with proper distribution. If the system is out of balance, more heat must be added or removed depending on heating or cooling, which will lower the efficiencies of the system and generates additional costs.

This course provides a working knowledge of the hydronic system operation and will familiarize the reader with piping system layout and operation, as well as provide an awareness of common circuiting arrangements. Topics to be discussed include auxiliary hydronic system components such as pumps expansion tank, terminal units and distribution piping and fittings.
In this course, you are required to study the US Corps of Engineers Construction Engineering Research Laboratory (USACERL) technical report 99:20, May 1999 Appendix E.

Course Content

US Army Corps of Engineers Construction Engineering Research Laboratory (USACERL) technical report 99:20

The HVAC equipment configuration and variants available in the market today provides many options. The hydronic system is essentially an all-water system where the space heating and cooling is transferred by means of distributed hot or chilled water piping. When the conditioning is transferred by a combination of heated/cooled air and hot/chilled water, then the system is termed an air-water system.

Hydronic systems may be divided into several general categories:

• Single pipe system
• Two pipe system
• Three pipe system
• Four pipe system
  

Single-pipe systems are limited in both their ability to deliver high volumes of steam (that is, heat) and the ability to control the flow of steam to individual radiators (because closing off the steam supply traps condensate in the radiators). Because of these limitations, single-pipe systems are no longer installed.

In two-pipe steam systems, there is a separate return path for the condensate and it may involve pumps as well as gravity-induced flow. The flow of steam to individual radiators can be modulated using manual or automatic valves. Very large scale systems can be built using the two-pipe principle. For example, rather than heating individual radiators, the steam may be used in the reheat coils of large air handlers to heat an entire floor of a building. Modern systems often use heated water rather than steam. This opens the system to the possibility of also using chilled water to provide air conditioning (air cooling).

In any water system, the water is circulated by means of one or more circulator pumps. This is in marked contrast to steam systems where the inherent pressure of the steam is sufficient to distribute the steam to remote points in the system. A system may be broken up into individual heating zones using either multiple circulator pumps or a single pump and electrically-operated zone valves.

Water expands and contracts as it heats and cools. A water-loop hydronic system must have one or more expansion tanks in the system to accommodate this varying volume of the working fluid. These tanks often use a rubber bladder pressurized with compressed air. This bladder bears on the water and maintains a roughly-constant pressure in the system across the expected change in fluid volume.

Excessive heat or pressure may cause the system to fail. At least one combination over-temperature and over-pressure relief valve is always fitted to the system to allow the steam or water to vent to the atmosphere in case of the failure of some mechanism (such as the boiler temperature control) rather than allowing the catastrophic bursting of the piping, radiators, or boiler. The relief valve usually has a manual operating handle to allow testing and the flushing of contaminants (such as grit) that may cause the valve to leak under otherwise-normal operating conditions. All hydronic systems must have a means to bleed air from the system.

The understanding and correct application of hydronics takes lot of experience and by installing correctly a good system can reduce fuel bills, increase longevity and comfort.

Quiz

Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.