Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
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9 points every architect, engineer, contractor and their clients should know about circulator theory and selection - sample slides. For additional support visit our visitor services page.

Our integrated design program has over 2100 slides illustrating architectural, interior design and HVAC engineering principles which contribute to indoor environmental quality and energy allocation for conditioning the occupants and building.

The following course materials on circulator theory and selection are samples from the lecture and based on a Steven Covey principle of "Begin with the End in Mind". They are a very small but important sample of the Covey principle and are provided here to give you an idea of what kind of materials we'll be discussing during the program.

The course is also registered with AIA and participants can earn up to 21 Learning Units.

For more sample slides visit our list of training modules.

Figure 1: Energy converters...that's what circulators are - they convert electrical energy to kinetic energy which develops the required differential pressure known as "head pressure" to rotate the fluid molecules around the system. Often called a "pump" they do not actually "pump" as in a well pump...nope - they circulate that's why they are called...circulators - go figure.

Figure 2: Circulators can be one of the least inefficient components of a system and the inefficiencies are exasperated when the circulators are incorrectly selected - which is often a result of poor to no engineering in establishing flows and head losses. Inefficiencies show up as noise, heat and vibrations. On a good day...a small wet rotor circulator might achieve 20% efficiency which means 80% of the input electrical energy did not go to circulating molecules. There are "smart" circulators available but even these have to be selected properly for optimum performance. Message - you don't pick circulators based on connection size nor your favourite have to analyze the system hydraulics and select a circulator so that it achieves maximum efficiency through the year.

Figure 3: Unlike in years gone by, the circulator technology of today offers several options in selecting the right product for the application. There are pro's and con's to each type and we'll discuss these in class.

Figure 4: Since fluid based system are always in a transient state, i.e. they are dynamic in that the loads change as the weather changes - it's important to control the circulator so overflow and under flow is not created as valves open and close. There are several control methods available for addressing the changing flows in a system as shown above.

Figure 5: As with all elements of design, there are laws which describe the relationships between energy and performance. Circulators, pumps and fans all follow the affinity laws - we'll demonstrate these during the lecturer.

Figure 6: Since circulators consume electrical energy based on head and flow, it's important to correctly prepare the hydraulic analysis so energy consumption is minimized. Using the affinity laws, simply by doubling the delta T (T) in the flow calculation the design flow will be reduced by 50%, the system pressure reduced to 25% and the power input to's easy to say - but cutting the flow in half has its own issues - we show you when and where you can apply such principles to ensure your clients are not over paying for circulator power.

Figure 7: One very useful way to analyze energy effectiveness in HVAC systems is to compare the electrical energy to the thermal energy.  What does this mean? It means you should always look at the ratio of heat being moved by electricity. We frequently find inexperienced designers using far too much electrical energy when designing system in comparison to those system designed by experienced engineers. This is not a trivial matter as the client becomes energy penalized for the life of the system when optimization is not done...we will give several examples of what to do and not to do to improve this ratio.


Figure 8: From the hour long lecturer we'll conclude with several message as shown above and in Figure 9 below.

Figure 9:  Circulators are an essential component and they have several relationships though the system but like all items they can be easily misapplied and this contributes to inefficiencies and instabilities in the system...something no client wants to hear about.

So there you have it, a few sample slides from our circulator theory lecturer...just a hors d'oeu·vre from our library of over 2100 slides addressing a small but important element of integrated design and radiant based HVAC systems. In the program we will get into this and a whole lot more? How much more? Well just follow the links to the other parts of our website and you’ll get a feel for the scope of materials that we’ll be covering.

See you soon.

Robert Bean, R.E.T., P.L.(Eng.)
Registered Engineering Technologist - Building construction (ASET #8167)
Professional Licensee (Engineering) - HVAC (APEGA #105894)
Building Sciences / Industry Development
ASHRAE Committees: T.C.61. (CM), T.C.6.5 (VM), T.C. 7.04 (VM), SSPC 55 (VM)
ASHRAE SSPC 55 - User Manual Task Leader

Note: The author participates on several ASHRAE and other industry related committees but be advised the materials and comments presented do not necessarily represent the views of these societies, only the president of the society or nominated representative may speak on behalf of the organization.

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