Print this page Variable Air Volume Systems - Principles, Applications & Acceptance Testing
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.
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
In this course, you are required to study the US Army Corps of Engineers Construction Engineering Research Laboratory (USACERL) technical report 99:20, May 1999 Appendix E.
You need to open or download above document to study this course.
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.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
