Summary
Radiant Heating and Cooling Systems
Radiant heaters are defined as units that have more than 50% of their heating output achieved through radiation.
Radiant Heating: High temperature, or infrared, units operate at over 300°F. There are three main types of high temperature units:
e High intensity units are electric lamps operating from 1800–5000°F.
e Medium intensity units operate in the 1200–1800°F range and are either
metal-sheathed electric units or a ceramic matrix heated by a gas burner.
e Low intensity units are gas-fired and use the flue as the radiating element Important safety and control issues to consider include both heater location and thermostat location.
Radiant Cooling: This is always achieved by using a ‘large area’ panel system. Issues for consideration include: space moisture level, location of insulation on the panels, and the response time of the system.
Thermal Storage Systems
Thermal storage can be “active” or “passive”.
Passive thermal storage uses some part of the building mass or contents like a thermal flywheel to store heat or cooling and to release it over time to reduce the heating or cooling load.
Active thermal storage takes place when a material is specifically cooled or heated, with the object of using the cooling or heating effect at a later time.
Chilled Water and Ice Storage
There are two reasons to use chilled water and ice storage: to potentially reduce installation costs and to reduce operating costs.
Chilled-water Storage: Storing chilled water is normally done in a large stratified tank, cold at the bottom and warmer at the top. One particular economical use of chilled-water storage is in the capacity extension of existing facilities.
Ice Storage: There are four main methods of generating ice for ice storage systems: coils with external melt; coils with internal melt; ice harvesting; and water in numerous plastic containers. Ice storage can result in smaller pipes, ductwork, and fans, when low-temperature supply-air is used. Ice storage requires less space than water for the same storage capacity.
The Ground as Heat Source and Sink
The ground can be treated as a large heat source or as a heat sink: one can extract heat from the ground or reject heat to the ground. There are three gen- eral methods of using the ground as a source or sink, the well, the horizontal field and the vertical field.
Occupant Controlled Windows with HVAC
People like to think they have control of their environment, resulting in a demand for occupant controlled windows, operable windows. Unfortunately, people are not good at assessing when to have the window open or when to close it.
Actual ventilation depends on orientation, building height, wind direction and wind speed. In mild climates, operable windows can be used to both ventilate the building and provide overnight pre-cooling with judicious building design and use.
Room Air Distribution Systems
There are four main types of room-air distribution: mixing, displacement, un- der-floor, and task control. Mixing is by far the most popular in North America and task control has yet to gain popularity.
Decoupled, or Dedicated Outdoor Air Systems
There are situations where mixing the outdoor air with return air and condi- tioning the mixture is not a good choice, like in warm, humid climates; or where fumes should not be recirculated with the building air.
Your Next Step
The objective of this course has been to provide you with an understanding of HVAC in general, and to introduce you to the more common systems used in the HVAC industry. We have not gone into great detail on any subject but hope to have provided you with enough knowledge to understand how sys- tems work and to decide what you want to know more about.
Fundamentals Series
For further study, ASHRAE has the following titles in this Fundamentals Series.
e Fundamentals of Thermodynamics and Psychrometrics
e Fundamentals of Heating and Cooling Loads
e Fundamentals of Air System Design
e Fundamentals of Water System Design
e Fundamentals of Heating Systems
e Fundamentals of Electrical Systems and Building Electrical Energy Use
e Fundamentals of HVAC Control Systems
e Fundamentals of Refrigeration
ASHRAE Handbooks
The four ASHRAE Handbooks are an excellent source of information on all aspects of HVAC and R. One volume is updated and published each year on a four-year cycle. Members receive a copy of the current year’s edition each year and copies can be individually purchased.
All four handbooks can also be obtained on a CD.
Fundamentals – This volume contains information on the properties and behavior of air, water and other fluids, and how they flow in ducts and pipes. It includes the theory and practice of calculating heat gains and heat losses through all types of building materials.
Systems and Equipment – This volume includes HVAC systems, air handling and heating equipment, package equipment, and general components such as pumps, cooling towers, duct construction and fans.
Applications – This Handbook begins with a section on how to apply systems and equipment to comfort, industrial and transportation situations. Following this, there is a section on general issues, such as operation and maintenance, and energy management. The Handbook finishes with general applications such as the design of intakes and exhausts, seismic restraint, water treatment and evaporative cooling.
Refrigeration – This volume provides very detailed information on all aspects of refrigeration equipment and practices, followed by sections on food storage, food freezing, low temperature refrigeration, and industrial applications that include ice rinks.
The ASHRAE Handbooks are, as a matter of policy, not commercial. They do not recommend any product. Therefore, they lack the reality (or dreams?) of the manufacturers’ sales and engineering materials. Don’t hesitate to ask manufacturers for sales materials and read them with an alert mind. Is there something here that could really work well in this situation? Is this too good to be true? If so, why? Be realistic, manufacturers put the best light on their product. The challenge for you is to find the product that will perform well in your situation.
Manufacturers
Manufacturers put significant effort into training their staff about their products. Do not be shy to ask them about their products. When choosing a product, ask the representative: “What would you suggest?” “Is it suitable?” “Is there something better?” “Is there something less expensive?” “Is there something more efficient?” “Who has one of these in and working and can I call them?” Be sure to ask more than one manufacturer’s representative for information, so you can get a different perspective on what is available for your application.
Keep asking, keep learning and have fun doing it.
Bibliography
1. ASHRAE Handbook 2001 Fundamentals
2. ASHRAE Handbook 2002 Refrigeration
3. ASHRAE Handbook 2003 Applications
4. ASHRAE Handbook 2004 Systems and Equipment
5. ASHRAE Design Guide for Cool Thermal Storage, 1993
6. ASHRAE Underfloor Air Distribution Design Guide, 2003
7. ASHRAE Humidity Control Design Guide, 2001
Epilogue
This story is not a part of the text of the book. I have heard and read a number of variations of it over the years. To me, it speaks of the importance of what we are doing, and what we can be doing, as members of this profession:
Long ago a king decided to go out on his own to see his kingdom. He borrowed some merchant’s clothes and dressed so that no one would recognize him.
He came to a large building site and went in while the gatekeeper was dealing with a delivery of huge wooden beams. As he walked around the site he came upon a stone- mason, who was chiseling at a large piece of stone.
“What are you doing?” the king asked.
“Oh, I’m making this stone to fit that corner over there.” said the man, pointing.
“Very good.” Said the king, and walked on. The king approached another stonemason and asked “What are you doing?”
“I’m doing my job. I’m a stonemason. It’s great working here, lots of overtime, enough to pay for an extension to the cottage.” said the man with a big grin.
“Very good.” said the king, and walked on.
The king stood and watched the third stonemason, who was carefully working on a detail, before asking him “What are you doing?”
The man paused, and looked up, considering his reply. Then he answered “I am building a cathedral.”