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