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By Todd Dorius
Building Automation Article Use Policy
Another area of potential energy savings relates to the ventilation, or outside air, component of an HVAC system. Using carbon dioxide (CO2) monitors in return air, smart systems can reduce outside air to a level of real and not perceived ventilation needs.
In most climates, this set-up can save significant energy, although savings will depend on building operations.
Even in an office environment, occupancy levels can be low, such as on and around holidays. For example, if an open office space was at only 25 percent occupancy before a long weekend, a ventilation system designed to bring in a set amount of outside air would cool the space too much, later requiring more reheat than usual.
But a system set to look at actual conditions would lower ventilation levels, as well as most parameters of the overall system, including fan speed and boiler loads.
Schedules are another important part of the BAS in controlling energy costs. The BAS in many facilities, such as school buildings, are programmed to go into night setbacks during off-hours. They resume normal settings when the building is scheduled for occupancy. Most BAS properly predict these times with optimum starts and stops for energy reduction, but few have been programmed to take advantage of off-time conditions.
In climates with high daily temperature ranges, buildings can be sub-cooled at night to lower the cost of optimum start-ups. If a building was sub-cooled on a cool evening, items in the building would perform like ice cubes, absorbing the cooling load when the building becomes fully occupied. This could be considered a poor person's ice storage. Night cooling also can result in monetary savings because most utilities offer better pricing in off-hours.
Scheduling also can be an energy-saving tool for hot-water systems. Most domestic hot-water systems have recirculation systems. These are wonderful for the first user in the system, but they become redundant.
Facilities Can Take Greater Advantage of BAS Features
Focus on Ventilation and Scheduling Pays Energy Dividends
Energy Efficiency Can Flow from Attention to Pumps, Fans