Lighting and Ventilation Control Systems

How a building manages air movement both into and out of the building as well as circulation within the building has a significant impact of how efficiently a building is run, and on ensuring that levels of indoor air pollutants and humidity are kept within acceptable levels.

At its most simple, lighting control can be as basic as wiring different lights or batches of lights onto separate switches and manually switching to get the desired illumination.

The above strategy can also be applied to dimmable lights with a manual dimmer switch.

A step up from this is to use passive infrared or microwave sensor switches to control illumination. This approach is generally applied to areas people transit through – corridors, car parks, and external lighting. These controls a are either built into each light, or are separate items installed to control a batch of lights.

PIR / Microwave sensor controls generally have 3 controls governing how dark it must be for the light to turn on, how sensitive the switch is to detecting a person (how close they are before the light turns on), and how long the light stays on after it last detected a person's presence.

Also to be considered as simple “lighting controls” are blinds, curtains, external shutters and LCD privacy screens (switchable LCD privacy glass).

One of the first such systems was Digital Addressable Lighting Interface (DALI).

DALI works by sending addressed signals over a mains AC circuit to up to 64 lights or groups of lights with the signal wiring going to each lamp in series, and can switch off or dim each light individually.

The main limitations of the original DALI system are that it is limited to 64 control nodes, and that the control wiring is mains voltage AC so requiring appropriate electrical insulation.

More modern control systems generally use a DC system with a maximum 10 volts with brightness controlled by the voltage of the DC control supply. Traditionally, this used 0-10 Volts, however most LED lighting cannot dim smoothly all the way down, so this has tended to be changed recently to 1-10 Volts. Another version raises the control voltage to dim the lights so that in the event of a light being disconnected from the control system it defaults to full brightness without a control system. In addition, other devices like light meters, fire alarms and microwave sensors can be connected into the system as control inputs automating the lighting control re occupancy, light levels, etc. and to activate warning lights should the need arise.

Each light has one exclusive signal wire, and one shared. Whilst the system overcomes the addressed node limitation of DALI, and uses safe low voltage DC, setting up large systems becomes a major task as cables of several hundred cores (telephone cable) might be needed depending how many lighting control channels are used.

For stage and theatre lighting, it is common to use a system called DMX 512 which offers 512 channels of lighting control – with multicoloured lights having separate channels for each LED colour operated through a virtual or hard wired mixing desk with a slider for each colour / control parameter on each light.

Wired connections tend to be a little more robust than wireless, and if controlled by a computer isolated from the internet, or behind a decent firewall can offer a high level of security from hacking attacks. If controlled by a device with a connection to the internet, the use of suitable passwords and security protocols is strongly recommended.

With a wireless system, new addressable lights can be installed without any rewiring using the existing electrical connection. The control arrangements use Bluetooth, WiFi, or similar, and the “address” of each light just needs to be programmed into the device used to run the control program. Older systems tended to use Bluetooth, however more recently and in conjunction with the rise of 5G broadband, and connect either to 5G wireless or local WiFi using Internet of Things protocols allowing a near infinite number of controlled devices.

 Note :- Some aspects of choice selection are likely to be set down in regulations such as those relating to fire safety.

 Remember your security protocols.

 

In principle the processes of ventilation control are very similar to lighting control, and can  be handled using a similar control interface.

Ventilation control broadly breaks down into

•  Controlling natural ventilation such as electronically controlled opening of windows and vents. This will often allow “stack ventilation” using the chimney effect to keep a building acceptably cool without air conditioning in moderate climates.

 

• Regulation of mechanical heat recovery ventilation – using a humidistat to adjust the amount of air exchanged according to humidity, and valves to open and close a heat recovery bypass allowing hot air to be vented in summer without recovering excess heat. (Often the air entering buildings through such systems will be filtered to remove pollen and various forms of particulate air pollution.

 

• De-stratification and cooling fans – the same fan can be used slow in winter to recirculate heated air down from ceiling to floor in high rooms, and in summer to create a cooling breeze) ideally in conjunction with opening windows.

 

• Automated Opening Vents (AOV) – roof level ventilation with or without fan assist drawing air up from a fire escape staircase to enable people to escape in the event of a fire without asphyxiation by smoke inhalation.

 

• Fan speeds in commercial cooker hoods could similarly be automatically adjusted according to heat and humidity, and whether or not cooking equipment is in use.

 As with lighting Controls, much of the above can be wired or wireless with various input sensors such as thermostats and humidistats feeding information to the control program.

 In industrial settings, it may be desirable to adjust ventilation according to various monitoring hardware to manage the levels of dust and pollution including gases such as CO and CO2 both incoming and outgoing.