It is well known that Commissioning of new buildings is a great way to save energy and money. Likewise, Re-/Retro-Commissioning existing buildings is an extremely cost effective way to re-capture those energy savings that have been lost over time due to changes and failures in the Building Control Systems (BCS). There should be a better way to continually maintain energy savings over time. A superior solution is to use the existing BCS. Most buildings of any size or complexity are designed with a BCS to handle the complexities of an HVAC system. Most of the complexities are present to reduce operating costs, otherwise, all the BCS needs to do is to maintain a comfortable working environment by controlling space temperatures, humidity and air quality. To reduce operating costs, the BCS performs all kinds of additional, somewhat complex operations, as listed below. 1. AHU Scheduling - Schedule the air handler off after business hours with higher or low space temperatures and return to operation in time so that space temperatures are acceptable by the time building occupants arrive. 2. Air-Side Economizer - When outside air conditions are cool enough, bring in increased amounts of air to help satisfy the building's internal loads. 3. Exhaust Air Energy Recovery - Recover energy from continuously exhausted air and pre-heat or pre-cool the incoming make-up or ventilation air. 4. Heat Energy Recovery - Recover energy from HVAC or other compressors to heat domestic hot water or for space heating. 5. Supply Air Reset - Reset the air handling unit supply air temperature when cooling loads have decreased to reduce supply air volumes and/or reheat requirements. 6. Demand Controlled Ventilation - Adjust the amount of ventilation air based on occupancy levels. 7. Maximize Cooling System COP - Operate cooling tower or condenser fans longer during cooler weather to reduce compressor pressures and result in lower system power requirements. 8. Lighting Scheduling - Schedule the lighting systems in larger, open areas off after business hours and back on again in time for building occupants when they arrive. After a building is occupied, all of these additional complexities must be maintained by building maintenance. This is a lot of extra work for features that, if they fail to perform, there is usually no consequence to the building occupant. If the air handlers or lighting systems do not turn off after business hours, who would even notice, except, perhaps, the cleaning crew. If the heat recovery units stopped working, a boiler or electric heater will take over. If the HVAC system does not bring in more outside air to cool the building, the air conditioning compressor will handle the load. For these reasons, building maintenance has no real incentive to repair these systems when they fail. The only real consequence is an increased energy bill, which is paid by someone else. The solution that is commonly used today is hiring a consultant to "re-commission" the building. Although re-commissioning is less expensive than a comprehensive energy audit, it takes time to select a firm, negotiate a fee, perform the on-site services, evaluate the savings and document the results. However, even if this is done on a consistent, regular basis, the increased operating costs due to failed or disabled energy saving features have been paid between the re-commissioning events. A more efficient, less expensive method is to utilize the existing, full time, around the clock monitoring system, the existing building BCS. Conventional BCS's use temperature sensors for feedback to control space temperatures to a setpoint, but energy savings features typically have no feedback. BCS's issue commands and assume that they were successful. A disconnected wire, a manually closed valve, or a defective contactor can render BCS commands useless and misleading. However, installing sensors in key places can provide essential feedback to the BCS that can be compared to an expected condition. If the results are negative, the event is recorded, displayed in a dashboard and transmitted to the appropriate people, such as the building owner, maintenance or consultant, for action. With the addition of "feedback" sensors coupled with additional programming and remote monitoring, an existing BCS can be transformed from a really "dumb" system for maintaining energy savings to a "smart" one that will monitor, control and maintain energy savings features that the building owner has already purchased in the BCS.
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