Energy Efficiency tip of the day (HVAC system mode of operation in hot weather regions)

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In the hot weather regions HVAC units are usually operated 24 hours on all days during most of the year, with the thermostat set point unchanged.

Neither the start and stop hours nor the thermostat set point of HVAC systems are set to match the occupancy hours of building facilities.

Energy savings can be achieved by using the following operation schedule of HVAC systems:

1. Night schedule setting

·      Switching off portable air conditioning units, PAC, or central AC units at night when the building is not occupied, and switching them on in the morning two hours before the start of office hours. This function can be performed manually by using the programmable timers of PAC units, or via a Building Maintenance System, BMS.

·      Alternatively, night setting can be employed based on normal occupancy times for the area or room.

·      Once activity is detected, and the area or room is identified as occupied, then the space temperature set point shall be set back to the normal set point value.

·      This is achieved by changing the thermostat set points to be 24 °C during occupied periods of building facilities and 28 °C during the unoccupied periods.

·      Use a basic operating rule : i.e. cool to the highest temperature possible and heat to the lowest temperature possible.

2. Space temperature setting

·      Automatic temperature reset control functions can be used to minimize the energy consumption of the cooling and heating systems by resetting the space temperature set point based on occupancy within an area for each system; if no activity has been detected for a predetermined time period (e.g. 10 minutes), then the area or room is determined to be unoccupied.

In the next parts I will present more energy efficiency tips related to HVAC systems Operation and maintenance

Magdy Aly

Energy manager, Energy efficiency consultant Passionate to help others to save Energy and Environment.

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