Two Position and Floating Responses in BAS Part 4 – Building Automation Systems Training
https://www.youtube.com/watch?v=UOwRKxTjoOY&t=397s
Welcome to building controls part 4 to position and floating responses. This is the fourth course in the building controls series if you have not already done so please participate in building controls 1 2 & 3 prior to taking this course. At the completion of this course, you will be able to describe the two position control response. How floating control methods are addressed and you will be able to employ an interactive example, which simulates a changing variable air volume box.
This class is one of a sequence that will provide you with an overview of basic control technology used in buildings so that you will understand how it can contribute to energy efficiency the purpose of this course is to address the two position and floating responses.
A two-position control response is the simplest kind of response that can be made from a controller when a certain condition is met. The controller enables a digital output to be turned on when a second certain condition is met. The controller disables that digital output or turns it off, let’s look again at the graph we looked at when discussing terminology and apply a cooling application to it.
The thermostat in most residences or homes is a type of two position control when you move a slider or push a button to change the desired temperature, you are changing the set point. Let’s say we put that set point at 23 degrees Celsius or seventy three point four degrees Fahrenheit the thermostat would then have a certain range.
It operates in a common range might be plus or minus one degree the way to position control would work is if the temperature gets above 24 degrees Celsius or 75 point two degrees Fahrenheit the cooling system would be enabled it would be turned on if the temperature drops below 22 degrees Celsius or 71 point six degrees Fahrenheit the cooling system would turn Off.
The system is designed to operate within a 2 degrees Celsius differential in Fahrenheit that would be a three point six degree differential of course. The temperature sensor only being in one spot for your entire house is not always the best application also you will notice that there is no adjustment in how quickly or how cold the air is being delivered. It is simply being delivered or not with an allowable differential for a single zone system that is fairly stable this is an acceptable solution other systems give more flexibility and precision for a higher price.
Let’s summarize some of the information that we have reviewed in this course. A two position control response is the simplest kind of response that can be made from a controller. This is simple on-off control when a certain condition is met the controller enables a digital output to be turned on when a second certain condition is met the controller disables that digital output or turns it off a differential is the difference between the setting at which the controller operates at one position and the setting at which it changes to the other position.
Floating control is used to create greater stability in a system if the value is in an acceptable range it should not be touched stability is needed to avoid constant changing of equipment within the neutral zone. The controller output does not change even if the input changes the output changes only in response to an input outside the neutral zone range
In the next section of building controls, we will move on to proportional and PID responses.