Scheduling actions and events in a KNX building automation installation

How to schedule events in your KNX Building automation system

This blog post will show you how you can schedule events to occur at certain times in your KNX building automation system.There is a requirement in the building automation industry for certain events to happen automatically at certain times of the day. There are two ways to achieve this goal: first first way is through hardware, and the second is through KNX event scheduling software.

Here are a few examples of tasks that should be automated using a scheduler:

-          switch off all, or certain lights in a building at the end of the working day

-          switch off the hot water heater at a particular time of the day

-          place certain components into their energy saving (standby) mode on weekends public holidays

-          switch on the irrigation system to water the garden on certain days of the week

Option 1: Scheduling KNX events using hardware

KNX Timer

If a hardware solution is required, then a KNX timer module can be purchased from any of the KNX device vendors. This module will be installed in the electricity distribution board of the building or house, and configured via ETS to execute events at certain times.

The advantage of this option is the fact that the entire module is self contained, and can be installed directly in the electrical distribution board, without the need for any other I.T infrastructure.

The disadvantage of this option is the fact that these modules are rather costly, and require a KNX professional with KNX configuration software (ETS Professional), and knowledge of the system to be able to configure the device.

Option 2: Scheduling KNX events using software.

The second option is to have a KNX event scheduler application operating on a computer which will execute the commands as required. The user can then add scheduled events as they require.

The advantage of this option is that the configuration of the device can be changed at any time by the user, and does not require any technical knowledge (providing the devices have already be assigned group addresses when they were installed)

The disadvantage of this solution is that there is a requirement to have a PC or server running to execute the commands. Typically, a building with  KNX would automation would have a PC or server running in the building to serve data for KNX visualization and data logging visualization and data logging, which means that the software could be run on the same machine.

How to save energy in a building on your HVAC systems

Part 2 : How to save up to 70% of your energy costs in your building on your HVAC systems.

The term HVAC is often confusing to electrical professionals. In the building context, HVAC stands for Heating, Ventilation and Air Conditioning (not High Voltage Alternating Current).

In general, HVAC consumes the largest portion of our energy in a building.

The easiest and most cost effective way to slash your energy bill in a modern building is by using variable speed drives to control your ventilation.

Here’s why:

Traditionally ,there are shutters at the air inlets to a building which channel air from the fan to , through the air ducts , into the room. When the user wants more air, they open the duct. When the user wants less air, they close the duct. All the time, the fan motor is spinning at full speed - even though the building is only making use of 50% of the air flow.

Here’s the problem (and the solution)

When a motor spins, the flow of air or liquid is proportional to the shaft speed. BUT, pressure is equal to the square root of shaft speed, and , crucially, energy used is equal to the cube root of shaft speed. That means that at 50% required air flow, we are wasting more than 70% in electricity. 

OK, that’s too much maths. Let’s put that into perspective:

Let’s say that a motor shaft is spinning at 1000 RPM (revolutions per minute) , and is consuming 10 KW of electricity.If the building requires 100% air flow, then that means that the vents will be 100% open, so we will be making full use of the energy input.

BUT, if we only needed 50% of the air, and we closed the vent 50%, then we would have high pressure in the vent (since we closed the valve to 50%), but our motor would still be using 100% of the available energy (10 kw).

Now, if we used a Variable speed drive instead of a standard DOL (Direct Online) approach to operating the motor, our motor shaft would be spinning at 500RPM to achieve 50% air flow. But (here’s the amazing bit) the motor would only be using 2.5KW of energy. That’s amazing!

A variable speed drive installation will typically pay for itself in a matter of months, and go on to repay the entire investment over and over again in its lifetime.

So, to save massive amounts of energy (and the penguins in the north pole), be sure to incorporate variable speed drives in your building design.

KNX Visualization

KNX Visualisation

This blog post will highlight an easy way to control your KNX installation directly from your PC.

There are many reasons to add a visualization package to your KNX building automation solution. For example, you may want to open or close the blinds in your office without leaving your desk, or to record the utilization of a particular room by measuring how long the lights and/or air conditioning are on each day.

Visualization also allows you to perform all functions in a particular room in the building, without actually being there. 

Types of visualization

There are three main types of visualization available on the market.  The first type is PC based visualization, where the visualization package runs as an application on a windows PC. The second type of visualization involves an embedded operating system on a piece of hardware which is mounted directly onto the distribution board in the building. These systems usually host an on-board web-server, and users can access the information via any web browser. The third type of visualization involves an "app" on a smart phone,  which can read and write data to and from the building via TCP/IP.

All three types of visualization have their place in the market, and it is impossible to say which is best, because different buildings will have different requirements.

An example of a very good PC based visualization software can be found here

Part 1: Save on your energy costs by implementing KNX lighting control.

This post will outline some of the easiest ways to save energy using KNX lighting control. In the post, I will lay out a few common options that you should consider adding to your building automation system design.

I'm assuming that you are not completely novice at this, and have installed LED downlights and flood lights,  T5 tubes and CFL wall lights, as opposed to the power-sapping "old school" incandescent and halogen bulbs.

Interestingly, the real power consumption of a CFL is more than double what is written on the package, because the power factor angle is conveniently not taken into account when providing the reading, but that's a story for another blog post.

Presence detectors

Presence detectors are devices that work in the same way as the PIR (also known as an “eye”) from conventional alarm systems, except that they are a lot more sensitive. A good brand of KNX Presence detector like the ones from ABB will also have built in lux meters (light intensity meters), so that the lights will not be turned on unnecessarily if there is enough natural light in the room.

Presence detectors send a “switch on” message onto the KNX bus whenever movement is detected in the room. Then, if no movement is detected for an amount of time (you can choose this time), it will send a “switch off” message onto the bus so that the lights can be turned off.

It is important to use good quality presence detectors that can detect small movements , otherwise (I have seen this in a building – it is funny to watch) the people in the room will be left in the dark if they sit still for too long, and they will need to wave their arms to turn the lights on again.

The energy saving from presence detectors comes primarily from our lazy nature as human beings. When going into a room, and leaving it again, people are often lazy to switch off the light again. The result is that a massive percentage amount of the total energy for that room will be wasted.

Presence detectors also make the use of a building more easy and functional. I work in an office building where all lighting is automated (ok, I was the person who did the automation, so maybe I am biased)

Nonetheless, when I go to another office building that is not automated, it is suddenly strange for me to turn on the lights manually. I think to myself “why doesn’t the building know I am here”?

I also use presence detectors to turn off the air conditioners when nobody is present in the room. If you work in an office, and have ever left the air conditioner on overnight accidentally, and needed to sit in a “fridge” the next morning, you will know what I am talking about.

Brightness control

Most rooms in a building allow a considerable amount of natural light into a room.

The maximum available natural light is next to the window, but the natural light decreases further into the room.

It stands to reason that if a luminary (light fitting) next to the window is at full brightness, then that electricity is being wasted. However, as the distance of the fittings from the window increases, so the brightness of the lights must also be increased.

Another advantage of dimming a fluorescent tube, is that the life of the tube is significantly increased as opposed to being left at 100% brightness. This saves on the cost of maintenance, as well as of the tubes themselves.

KNX dimmers which cater for brightness control can be used to effectively light a room to the required brightness without wasting any power on unnecessary light. They will also require a lux meter to determine the light level in the room at the time.

If your dimmer does not support this function, then a cost effective way of achieving this goal is to use a scene to switch on the lights instead of simply an on/off signal.

For example, if you have 8 light ballasts in a room, create 8 Group addresses for that room (one for each ballast), and set the operation of the light switch to send a scene when pressed.  

Then you can define the brightness for each ballast (increase the percentage for each ballast further from the window). Please remember to still allow “all on/off” for night operation.

Using the above simple techniques, you can really minimize the running cost of your building associated with lighting.

Be sure to see my next blog to see how to save energy using HVAC.

How to save on your energy bill using KNX.

How to save on your energy bill using KNX.

If you know anything about building automation, you will know that KNX is the worldwide standard in building automation and control. You will also know that you can achieve substantial energy savings using KNX.

Your next question, however, will be “How is this saving achieved?”

My next few blogs will focus on exactly that: How is this energy saved? How should I design my building automation installation for maximum energy saving? What products should I use?

 There are 3 main areas that I like to focus on when saving energy, and I see them as the “low hanging fruit” when it comes to energy saving.

1)      Lighting

-          I will show you how to save the maximum amount of energy using lighting

2    2)      HVAC

-          I will show you how I use HVAC (Heating, ventilation and Air conditioning) in a way that is comfortable for the building occupants, but still energy efficient

3   3)      Conditional building states

-          I will explain to you how you can minimize the energy consumed by your building by putting the building into different “modes” during different times of the day, year or usage statistics.

Using the above three techniques, you can save up to 70% of the energy required by your building.

Over the next three weeks, I will be going into detail on each of these three key items including products to use, techniques, how to set them up in ETS4, etc. So be sure to check back for more.