Figure 6 National Oilheat Research Alliance 27 For example: We measure out a zone to be a total of 80 feet, including all the elements and the supply and return piping to the boiler. Head = 80 X 1.5 x .04 = 4.8 foot of head. A circulator that can provide a total of 2.7 gallons per minute and overcome 4.8 feet of head is therefore required. This information and calculation is often shown in circulator performance curves. Figure 6. Looking at these performance curves, the figures along the bottom of the chart indicate flow in gallons per minute (gpm), and along the left side of the chart is the head produced in feet. The curves represent what a circulator can produce. Using the information that was calculated for the zone, 2.7 gpm with 4.8 foot of head, we plot that point on the curve. Now look for what circulator to choose based upon the need of the system. If circulator #1 was chosen for the project, it would not heat the home adequately when it got colder outside. The ideal circulator for this job is #3. Three-speed circulators Three-speed circulators are specifically designed for the wide range of flow and head requirements of today’s heating systems. Their threespeed switching capabilty provides fine tuning control to match a wide combination of system requirements. They are an ideal replacement circulator type to use in any emergency no-heat call. Figure 7. When using a 3-speed circulator, use the same calculations as before to choose the proper speed setting the circulator will use. In this case, the setting should be Low Speed. Figure 7
NORA Advanced Hydronics
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