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Get Your HVAC System in the Zone

Key Points
  • To improve HVAC efficiency, start at the zone level and work back to major system components.
  • Zone-level equipment includes mixing dampers, reheat coils and thermostats.
  • Preventive maintenance including regular inspection and repair can significantly reduce energy costs.

Source: www.bls.gov
HVAC

You want to improve the performance of your heating, ventilating and air-conditioning (HVAC) system, but it's so complex. One way to tackle this problem is to start at the zone level (conditioned space) and work your way back to major system components. Going in this direction allows you to take advantage of downstream savings before taking on more complicated (and costly) projects.

As an example of this approach, repairing corroded dampers will ensure that they open and close properly, reducing energy waste and increasing comfort. This fix may also reveal additional savings opportunities, such as resetting controls or rightsizing equipment.

Optimizing zone-level performance

Zone-level equipment includes mixing dampers, reheat coils and thermostats that control the conditioned space. As facilities age, this equipment can fall into disrepair or out of calibration, reducing overall system performance. Fixing zone-level problems can save energy and increase occupant comfort. Typical zone-level, energy-saving opportunities include:

Inspect dampers. Without regular maintenance, dampers often become frozen in position, rendering them ineffective at regulating air flow and saving energy. Locating and repairing non-functioning dampers can be time-consuming and expensive, but it can pay dividends in increased system efficiency and enhanced comfort.

Recalibrate thermostats. In systems with pneumatic controls, recalibrate thermostats every 6 to 12 months to ensure that the temperature is regulated accurately and efficiently. Although you should check calibration in response to a problem or complaint, proactive maintenance can optimize system efficiency and energy savings.

Maintain reheat coils. Inspect reheat valves and coils to ensure that they respond appropriately to control system commands. Verify the capacity of the reheat coil by measuring its power input with an amp probe and comparing it to the nameplate value. If the measured value is significantly lower than the nameplate value, replace the coil.

Shut off reheat systems in summer. If your facility includes a constant-volume reheat system, consider disabling it during the cooling season. With electric reheat systems, it's possible to power off reheat coils at the breaker, saving energy. In certain situations, it may be necessary to leave some reheat coil breakers active to maintain comfort.

Control static pressure. Dual-duct systems typically include static-balance dampers to regulate static pressure in hot and cold ducts in response to zone demands. Over time, these dampers can fall into disrepair and fail, resulting in wasted energy and reduced comfort. Regular inspection and repair will help optimize system performance.

Looking for more ways to improve efficiency? See Finding Hidden Energy Savings in HVAC Systems.