This option will set the automatic control function to MANUAL CONTROL and will be based on the GAIN calculation method.
To use this lighting function you will need to have calculated a DAYLIGHT FACTOR within the zone for which the lighting function will be referencing (the 'control zone').
To use the function, under the Control Logic area on the dialog, set the Control Type to "Manual Control" on the drop-down list. Then choose "Gain Method" from the Calculation Method drop-down options. Under the Parameters area, choose whether the applied zone will act as the control zone. The applied zone will be the zone to which the internal condition is applied. Otherwise you will need to specify which zone in the model will act as the control zone. If you select another zone from the drop-down list to be the control zone, its illuminance levels will determine when and how the lights will be operated within the applied zone.
The calculated lighting gains will be a function of the minimum and target room illuminance levels. You will need to input the illuminance level at which the lighting gain will be at its maximum value, and specify at what illuminance the lighting gain will be at its minimum value. You can do this by entering the maximum and minimum gains in W/m^2, or you can enter the lighting efficiency in units of W/m^2/100lux and then input a minimum gain as a percentage, this will be the percentage of the maximum lighting gain that will be used when the natural room illuminance exceeds the target room illuminance. The maximum lighting gain will then be back calculated from the efficiency value.
The lights will operate as follows, in the first occupied hour the function will look to see what the illuminance level is, and if it is at or below the target room illuminance. If the illuminance level is at (or above) the target illuminance then the lighting gain will be set to the minimum value. So the lighting gain during the first occupied hour will be the minimum gain, as determined by the Lighting Control Function dialog box. In the second occupied hour, the function will look to see if the illuminance level has changed. If the illuminance level is still at (or above) the target illuminance then the lighting gain will not be changed from the value that was used in the first hour, but the function will look to see if the lighting gain needs to be updated at each hour. If the illuminance level has dropped below the target room illuminance, meaning that the room will now have less access to natural daylight than it did during the previous hour, then the lighting gain will be increased. The lighting gain will be increased linearly as illuminance levels decrease linearly, until the minimum illuminance level is reached, at which point the lighting gain will be set to the maximum value. The maximum lighting gain will be determined by the value you will have already input on the Lighting Control Function dialog.
The defining characteristic of the manual control function is this, during the occupied period, if the illuminance level were to fall at any hour, the lighting gain will not be reduced. This is to model occupant behaviour consistent with turning lights on to give more light, but then not turning them off when more daylight becomes available.
If you need the lighting gain to reduce at hours when the illuminance level has increased, then you should select the photocell control method for your automatic lighting control function.
Example - mlclg,0,10,500,18.75,1.25,999
The function string begins with a '0', which indicates that the control zone is the applied zone. Otherwise, the first number will correspond with the zone number, as shown on the Zones table.
The next number is '10', which means the minimum illuminance level is 10lx, at which point the lighting gain will be at its maximum value.
This is followed by '500', which represents the target room illuminance.
The next number is '18.75', giving the maximum lighting gain in W/m^2, followed by the minimum lighting gain of 1.25W/m^2.
The final '999' in the function string means that zones with area greater than 999m^2 will use the maximum lighting gain value.
Let's look at a worked example, based on this function string. Assume the zone area is smaller than the area cut-off value. Suppose the illuminance level in the first hour is 500lx, which is the target room illuminance. This means that the lighting gain will be at its minimum value, which will be 1.25W/m^2. At hour 2, the illuminance then falls to 300lx, so the lighting gain will increase to roughly 8W/m^2. At hour 3, the illuminance level increases to 400lx, but the lighting gain will remain at 8W/m^2 because this is manual controlled lighting. At hour 4 the illuminance level will fall to 200lx so the lighting gain will be increased to approximately 12W/m^2. When the illuminance level is reduced to 10lx or below, the lighting gain will be at its maximum value of 18.75W/m^2. The lighting gain will not go below this value for the remaining occupied period.