by Nicholas Neiley, Senior Project Engineer
As we head into the shoulder heating season in the Northeast many facility operators struggle to maintain building comfort and system efficiency. The shoulder heating seasons typically extends from March through May and October through December. Temperature swings of 30-40F in a single day are not uncommon which place stress on facilities system’s ability to maintain comfort and efficiency through the wide range of outdoor conditions. This is also a perfect time to observe how efficiently your systems are at reacting to a wide range of conditions.
One of the greatest challenges in any facility is the transition between heating and cooling modes. This is a situation that often occurs daily during the should season as outdoor air temperature rise and fall. The first key to improving system efficiency is understanding how your system is intended to work. Review your buildings design and as-built documents to gain an understanding of the intent. Documents to review would include design intent/basis of design narratives, control sequences, one line diagrams, and systems manuals.
After gaining an understanding of how the system is intended to work the next step would be to review system operation to identify areas of concern. If BMS trend data is available this is your greatest asset when searching for areas of improvement. Check space temperature trends to identify areas of constant heating demand or widely fluctuating temperatures. These are your trouble spaces which need to be investigated further. Typical issues to check for are control valve leak by, clogged strainers, and low system pressure or flow. The end use issues should be addressed prior to investigating total system efficiency improvements as one bad terminal load can drive your entire heating system.
Once any terminal issues have been documented and corrected the next step is to review total system performance. A good place to start is verifying outdoor air resets, system enable temperatures, and morning warmup sequences are adequately adjusted. These sequences can be checked by verifying the worst-case situation. For example, check your heating control valve positions at the minimum and maximum outdoor air reset schedule ranges. If you find many valves are open or closed this would be a good indication the reset schedule needs to be adjusted.
After checking the heating system is operating effectively as designed it may be time to dig deeper for efficiency gains. Can control sequences and equipment operating be modified to reduce energy usage while maintaining system performance? Is it possible to shut down the heating system earlier in the year or start it up later in year? Can motors or boilers be replaced with more energy efficient models?