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Commissioning

What is commissioning?
The IESNA Handbook, 9th Edition offers the following definition of commissioning, "... a systematic process that ensures that all elements of the daylighting system perform interactively and continuously according to documented design intent and the needs of the building owner." Commissioning involves equipment set-up procedures, calibration, the input of control settings and the tuning to fit the system to the location and conditions in which it is installed. A first step in commissioning anything is to verify that the right equipment was installed properly and that it is functioning. Beyond that, commissioning is different for different systems.

For photosensors the next step in commissioning is the process of making adjustments to the control algorithm parameters to tailor performance to the specific application. These adjustments are typically done by setting potentiometers or dip switches on the photosensor. The adjustments generally do not change the form or type of control algorithm, but determine constants such as set points and signal ratios that are part of the control algorithm. The constants and the operational characteristics that they affect are unique to the different types of control algorithms. Commissioning of the three basic types of control algorithms are separately discussed in this tutorial.

To help better understand the commissioning process, a distinction between installation, calibration and parameter adjustment is necessary. Installation is limited to fixing the equipment in place and making the appropriate electrical connections. Installation is not part of the commissioning process. Commissioning takes place after the equipment is installed.

Calibrating is often used synonymously with commissioning, but calibrating is only a small part of the commissioning process. Its precise definition concerns associating an instrument readout with a known unit of measurement. For example, a thermometer is calibrated by immersing it in an ice-water bath and associating the corresponding reading with 0 C. Similarly, an illuminance meter might be calibrated by exposing it to a known illuminance from a standard lamp and then adjusting the readout scale so that the reading equals the known illuminance. There is more to commissioning than just calibration. Calibration might not always be necessary to do in the field after installation. For example, the temperature readout on a thermostat might arrive pre-calibrated from the factory, so once installed the device will accurately indicate the temperature. However, the heating and cooling system will not operate as intended until someone sets the thermometer to the desired temperature. Setting the temperature is part of the commissioning process in this example, whereas calibration is not.

The setting of the thermostat in the above example is a parameter adjustment. The desired temperature to maintain is one of the parameters used in the thermostat control algorithm to control temperature. Other parameters for a thermostat might include the cycle time, the range of acceptable temperature excursions, and time clock settings for multiple set points. Similar parameters exist for photosensors such as the maintained workplane illuminance level, and the rate at which dimming occurs. Depending on the type of control algorithm, a photosensor might have other parameter settings that allow the photosensor to deal with specific room conditions such as ceiling/workplane illuminance ratios.

Often times, however, people speak of moving the photosensor to different locations within the room to find the spot that best provides the desired control. By doing this, the person is searching for a convenient spot where the photosensor input optical signal is directly proportional to the workplane illuminance or whatever other lighting criteria the person is seeking. This should not be considered as part of a commissioning process because it is not a systematic process, but one of trial and error, and moving the sensor is not something that is readily done, but rather involves installation procedures (running wires, cutting holes in ceilings, fastening, etc.). To consider moving the sensor around as part of a commissioning process, the sensor must be readily moveable by the commissioning person (therefore no wires attaching the device to the rest of the lighting equipment) and detailed instructions would need to lead a person through a systematic procedure to determine the appropriate location.

Click next page to see more sections in Commissioning.


 
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