Step By Step

For those electrical contractors incorporating systems integration into their skill sets, many questions and strategies for doing so may appear. Consider this as a general guide to the basic elements of integrating a system. It is intended to help people who are unfamiliar with systems integration to ask the right questions. Hopefully, it will remind those who are actively engaged in it of some of the general principles.

First question: What is a system? According to Merriam-Webster, it is, among other things, “a group of devices or artificial objects … forming a network especially for distributing something or serving a common purpose.” This definition sits well with my preconceived ideas about a system.

Second question: What is Merriam-Webster’s definition of “integrate”? It is “to form, coordinate, or blend into a functioning or unified whole… .”

Therefore, I think a useful working definition for integrating a system is coordinating the function of a group of devices that form a network, especially for distributing something or serving a common purpose.

Since it is safe to assume we are talking about integrating building systems in this magazine, we must explore how that would work in some of the most basic forms of systems:

  • Lighting
  • Climate control (heating and cooling)
  • Safety (fire, security, etc.)
  • Communication (telephone, audio, video, computer, etc.)

In order to integrate systems, for example lighting and HVAC, the following steps are necessary:

  1. You first decide upon the device(s) that are the basic units of the system. For example, for lighting, one could choose a floodlight. For HVAC, one could choose a blower.
  2. These devices need to be remotely controllable. For example, in a lighting system, one could use a solid-state switch, or for HVAC, one could use a variable frequency motor drive.
  3. There needs to be a controller with at least one input and one output. The controller must have an input that accepts a command calling for a desired state of the system. For example, one could use the command “Turn on all lights” or “Heat the room to 70°F.” The output sends a signal to adjust the controlled device according to the command. For example, the output could be a 10-volt signal to energize the solid-state light switch or a 4- to 20-mA analog signal to control the blower speed in the heating system.
  4. Performance can be greatly improved by adding a feedback input, which informs the controller of the actual state of the system. For example, “The lights are on,” or “The room temperature at this moment is 67°F.”
  5. Integration can be carried to an even higher level by means of a building management system (BMS), which communicates with all of the different system controllers, in order to coordinate them. For example, with lighting and HVAC, you might want to bring an office up to a comfortable temperature an hour before the first worker is due to arrive and turn up the lighting to normal as soon as the first worker walks through the door.


What are the devices used for lighting? Sounds like a simple question, but it may not be so simple. One of my favorite sources for definitions of electrical building devices is the National Electrical Code (NEC), Article 100: “Luminaire. A complete lighting unit consisting of a light source such as a lamp or lamps, together with the parts designed to position the light source and connect it to the power supply. It may also include parts to protect the light source or the ballast or to distribute the light. A lampholder itself is not a luminaire.” I think that “luminaire” should be considered the basic unit of a lighting system.

The simplest device for controlling a luminaire is an on/off switch. Therefore, as I see it, the simplest lighting system consists of a switch controlling a luminaire. To remotely control a switch, you can use a relay, either electromechanical or solid-state, or a dimmer, which varies the light intensity.

A lighting controller can be a touchscreen, where the input is someone’s finger selecting a “scene,” which energizes a predetermined combination of luminaires to different light levels. The controller also can be a computerized device capable of being programmed to accept a variety of inputs, such as time of day, ambient light level or whether an area is occupied. The controller then can be programmed to use the input information to produce a lighting scheme that fits the needs of a particular occupancy.

Most manufacturers of solid state light switches and dimmers also make master lighting control panels and switch units.

Climate control

The basic units of a climate control system can be ceiling fans, air conditioners, electric baseboard heaters, hot water-based boiler systems, or blower-driven hot and cold air circulation systems. For example, these can be controlled by simple on/off switches, electrically activated valves, air blowers or electrically actuated dampers.

The type of controller depends on the kind of devices being controlled and the size and type of building. Homes use thermostats, which sense room temperature and generally send on/off signals to the heating or cooling devices. A thermostat can be a simple device whose input might be a slide-switch to select a desired temperature. The input also can have a variety of programmable “scenes” that call for a range of temperatures based on time of day, day of the week, etc.

Large commercial and industrial buildings and institutional structures, such as schools and hospitals, typically use blower-driven air systems. Modern HVAC systems use a technique called variable air volume (VAV), which involves a double control loop. The temperature in each room is controlled by changing the rate of flow of heated or cooled air by means of electrically actuated dampers. Changing of the damper position has the effect of changing the load on the blowers that move the air. The second loop, therefore, uses a pressure sensor in the air ducts to control the blower speed. Variable frequency drives (VFDs), which are similar to lighting dimmers but are more complicated, can electronically control motor speed over a wide range in response to the input from the duct-pressure sensor.

Safety and security

The basic controlled devices for fire alarm systems are audible and visual alarms, for example horns and strobes. The simplest fire alarm is an individual smoke detector with a built-in alarm; however, in the fire protection industry, these are not considered part of a fire alarm system. In a system, the alarm is activated by a fire alarm control panel (FACP) in response to an input. The inputs might be smoke detectors, flame detectors, heat detectors, manual call points or manual pull stations. The outputs not only activate warning devices but also might notify a monitoring service and/or the local fire department.

The basic controlled devices for automatic sprinkler systems are water sprinkler heads. The sprinkler is activated by a heat-sensitive release mechanism, which is built into the sprinkler head. When a high enough temperature is reached, the sprinkler head opens and allows water from the building’s water supply system to spray out. Flow and pressure switches with electrical outputs can be input to the FACP to activate the alarm system.

Physical security systems include access control, intrusion detection and video monitoring.

In access control for physical systems, the basic units are locks. In order to enable the integration of locks, they must be electronically controllable. There are a variety of locks operated by magnetic card readers or keypads. The information from these individual devices is connected to an access control panel, which authenticates the input and, if correct, sends an output that releases the lock.

Intrusion detection is based on a variety of devices that can sense the opening of a window or door or whether a room is occupied (e.g., a photoelectric beam; or ultrasonic, infrared or microwave-based sensors). The signals from these sensors are transmitted to a control unit, which will output an alarm to a warning device, such as a siren, strobe light or remote monitoring center.

The basic device in video monitoring is a camera, which can either continually monitor sensitive areas or be directed by an alarm panel to focus on a location where the system has detected an intrusion. The output of the camera is sent to a monitor for real-time viewing, or it can be recorded for future analysis.


Integration of systems can be fairly rudimentary. For example, some panels combine fire alarm and intrusion alarm controls. The trend, however, is for the controllers in the various building systems to have the ability to transmit inputs and outputs over common wired lines or use wireless transmission. This often is called building automation or a building management system (BMS). The controllers for the various systems generally have communication ports, which can transmit inputs and outputs. These are generally compatible with each other, so a single set of wires or fiber optic cables can carry information among all the controllers.

The ability to enable all these systems to interact with each other has come as the result of the development over the past several decades of standards for transmitting data using digital codes. The standards governing these codes fall into two general categories:

  • Rules defining the details of how the data is transmitted. An example is the voltage level of the coded digital bits called the physical layer.
  • Rules concerning how information is coded and how transmitters and receivers are identified, called the protocol.

Building systems connected to each other by copper wires or fiber optic cables are said to be part of a local area network (LAN). Systems also can communicate using radio frequency transmission through the air, called Wi-Fi.

The various specifications and protocols have been focused on improving the ability for systems to pass information from one to the other. Earlier systems tended to use proprietary standards designed by the various manufacturers for their own equipment. More recently, various industry sectors have developed open standards that many manufacturers would agree to in order to provide interoperability. For example, BACnet was originally developed primarily for HVAC, but some also use it for lighting controls. Another approach manufacturers are taking is providing gateways modules, which allow two different LAN systems to communicate with each other. Another development is the use of Ethernet as the standard for the physical layer and for assigning unique addresses to each device. This standard is used for transmitting information between various end systems and computers. Therefore, computers equipped with the proper software can program and monitor the controllers for each of the building systems.

The future

The ability to integrate and interconnect these systems will open up many possibilities for the future. It’s exciting to try to envision the possibilities. One could control lighting levels to adjust for using sunlight and to coordinate with HVAC cooling to minimize heating from the lights during hot weather. One could have special lighting patterns to coordinate with fire or other emergencies or fire alarms to trigger emergency control for elevators. Intrusion detection could trigger voice alarms.

Building systems are rapidly evolving from a series of niche specialties to a widely interconnected and coordinated group of functions. It will continue to become increasingly less possible for technicians and contractors to specialize in one particular area.

BROWN is an electrical engineer, technical writer and editor. He serves as managing editor for SECURITY + LIFE SAFETY SYSTEMS magazine. For many years, he designed high-power electronics systems for industry, research laboratories and government. Reach him at


About the Author

Edward Brown

IBS Columnist and Freelance Writer
Edward Brown is an electrical engineer, freelance writer and editor who draws on his years of practical experience designing industrial processing and high-power electronics systems. In addition to writing the Integrated Building Systems column for E...

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