Trane TRG-TRC014-EN manual Unoccupied Mode, System Configurations, period three

period three

System Configurations

notes

Unoccupied Mode

▲Main supply fan operates only as needed to maintain thermostat set points

▲Main supply fan controlled to maintain the system static-pressure set point

▲Outdoor air damper is closed

▲Terminal units maintain respective “unoccupied” space thermostat set points

Figure 69

In a typical commercial facility, the unoccupied mode occurs at night. The building does not require ventilation because it is not occupied, and the temperature in the perimeter spaces must be prevented from getting too cold (perhaps 60°F [15.6°C]) or too hot (perhaps 85°F [29.4°C]). Temperature control of the interior spaces is typically ignored because proper control of the perimeter spaces normally adequately limits the interior space temperatures. The top floor of the building may require temperature limiting for all spaces.

During the unoccupied mode, the following occurs:

nThe main supply fan cycles on whenever any perimeter space or a centrally located nighttime thermostat demands heating or cooling. If separate perimeter heat is installed and heat is demanded, it will operate and the main supply fan remains off.

nThe supply fan is controlled to maintain the static-pressure set point of the system.

nThe outdoor air damper is closed.

nAll terminal units with demand for central heating or cooling maintain their respective unoccupied temperature set points. All other terminal units remain off.

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