Controllers and Controlled Devices Part 8 in BAS – Building Automation Systems Training
https://www.youtube.com/watch?v=gT24EGfNfMc
This course you will be able to identify different types of controllers and describe how control devices change or maintain environmental conditions this class is one of a sequence that provides you with an overview of basic control technology used in buildings so that you will understand how it can contribute to energy efficiency in the previous class in this series.
We discussed the ways to use different control loops for different needs now we will look at the different classifications of controllers we’ll also see how the control loop is completed by control devices which take the actions that maintain or change current environmental conditions.
You primary/secondary application-specific or networking controllers point collection modules are also a type of control hardware sometimes these classifications can refer to Hardware specific design on the other hand a single Hardware controller may support several if not all of these functions so think of these classifications not so much as specific limitations of hardware but different ways to classify the functions or characteristics that the controller might have primary controllers are referred as such because of their processing and memory capabilities although the major distinction of a primary controller is its programming capabilities a primary controller can be viewed as a microprocessor with a clean slate therefore no matter what the required sequence of operations a primary controller can be programmed to function accordingly.
Primary controllers can be understood as having a dual purpose first they are responsible for
Controlling mechanical equipment although each primary controller is unique each will be equipped with a certain number of inputs and outputs in order to gather needed information and correspondingly control particular control devices a primary controller should be selected in accordance with its ability to handle all the points needed to control a particular piece of equipment in addition to this primary controllers have a real-time clock function allowing for schedules to be created although these schedules live in the primary controller they can be used to control other controllers as well.
Alarming and trending are further functions that can be supported by a primary controller data can be stored in a primary controller and that data can be pulled from the controller to create a graphical trend using software on a PC the controller can be set up to collect data at timed intervals to give an operator real time in historical data these trends can give insight into the way the HVAC system is operating for example the end user can trend or plot a
temperature in a room over a two-week period to ensure that the system is operating properly or discover factors that are
– a system failure alarms are generated by a primary controller and sent across the network to software on a PC to give the end-user insight into critical information needed to maintain facility conditions
– if the temperature rises above or drops below an acceptable level the end user will be notified allowing them to act as needed to fix the system secondary controllers are programmable but usually have less memory than a primary controller they do not contain a time clock and are typically limited on trends and i/o as well since they have no time clock on board they are not able to support time stamping of data or independent scheduling features.