SYSTEM DESIGN
By Bob “Hot Rod” Rohr
Go with the flow
when resolving heat complaints W
hen we use hydronic systems to move energy around, flow is one of the drivers. Think of hydronics as a fluid-based energy transfer system. As such, hydronics is used to heat, cool, provide DHW, and many processes in commercial applications. In many cases, a circulator pump is the “motor” that moves the fluid around the loop or circuits. As a troubleshooter, a common call is for a lack of heat or hot water in a home or building. My modus operandi was to start thinking of possible causes as I drove to the call. If it was a job I had installed, or had been to before, I would start running through the layout in my mind. To move or transfer heat energy we need both flow and a temperature difference (note, there are still some gravity powered systems out there, however, this article will focus on pumped systems). We do not always have the luxury of a system design or mechanical schedule indicating the equipment that is supposed to be installed. I would venture to guess most residential systems do not have adequate, if any documentation. So, we must make some assumptions based on practical experience and an overview of the system. It does not take a lot of effort to determine a lack of flow condition. It could be as simple as laying hands on the piping to determine if fluid is moving. Most volt ohm meters (VOM) have temperature differential heads for taking temperature readings. Contact thermometers are helpful and if you have one, an infrared camera is an ideal troubleshooting tool. If in fact you are using a circulator to move flow, it needs to be sized to the job at hand. Learn the steps to properly size the circulator. There is plenty of online training to help you acquire appropriate sizing skills. Being old fashioned, I still use the Bell & Gossett System Syzer tool. B&G also offers version 4 of its System Syzer program for PCs.
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Properly-sized circulator, so what’s next? Assuming the circulator has been sized properly, next up is a review of the installation. There are arrows cast into most every circulator. Many circulators have checks installed or in the box and those too are directional. Make sure these components have been installed properly; if that is not the case make it so as you update the system. You’ll appreciate it if the installer (maybe you) included isolation valves in the original installation. Note the “what not to do” graphic − these are best practice recommendations. You and I have seen these suggestions ignored and surprisingly the system may still work. It just may not work as well as it should and you might be able to improve it. You could pipe in a workable purge arrangement. There are pump iso-valves with purge ports built in. It is well worth the money to have a quick, easy and defined way to purge a loop. Many no- or low-flow conditions can be traced to inadequate purging.
