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Inverter driven air conditioning is more energy efficient, cheaper to operate and more profitable to install than its non-inverter driven equivalent. Here Neil Ballinger, head of EMEA at automation parts supplier EU Automation, explains how HVAC engineers can maintain the inverters in their customer’s aircon units. Do you remember cross country at school? It was exhausting; miles of seemingly pointless jogging and sprinting and, if the teacher was not looking, walking. If you were unlucky enough to be born before modern safeguarding measures were introduced, it probably also meant getting lost in the nearest woods.Why isn’t every installation an inverter driven unit, instead of the traditional single stage or dual stage models? My PE teacher, who seemed particularly vicious at the time, but in retrospect just knew about sports science than most, used to make us do something called fartlek as well. This meant long distance runs, incorporating elements of speed training by mixing up sprints with jogs and walks. The worst bit was starting to run again after a walk. That is exactly how the motor in your customer’s air conditioner feel if the units you fit are not inverter controlled. The motor has to act just like a runner doing fartlek — it sprints continuously, operating at full speed until the thermostat tells it the room is cool, then it stops. When the room gets warm, it starts again, powers immediately up to full speed and repeats the process indefinitely. Just like a teenage cross-country runner, it is the starting and stopping that is the tough bit. Furthermore, the unit probably doesn’t have to run at full speed to keep the room at the correct temperature, if the motor were inverter controlled it would speed up and slow down as the temperature fluctuates. Why isn’t all aircon inverter driven? We all know that inverter driven aircon is better than its non-inverter driven cousins. It can provide heating as well as cooling and the lifetime cost of use is less for the customer — because their energy bills stay low. The cost of installation is also higher because it is a more complex job, so it works out better for the contractor. It’s a win-win. The research firm Technavio even lists it as one of the key technologies driving growth in the HVAC market in its annual reports every year. So, the only question is, why isn’t every installation an inverter driven unit, instead of the traditional single stage or dual stage models?When contractors contact EU Automation to buy automation parts, for the units they maintain, they have given us another reason: maintenance Cost is a factor, but when contractors contact EU Automation to buy replacement motors and inverters, and other automation parts, for the units they maintain, they have given us another reason: maintenance. As HVAC engineers, we are not necessarily specialists in power electronics, and this makes inverter maintenance daunting. Microcontrollers and IGBTs (Insulated Gate Bipolar Transistors) are not beyond us by any means, but they can be intimidating. Personally, I would back an electrical or heating engineer over an electronics specialist in a problem-solving contest all day long; but that doesn’t solve the problem at hand. Furthermore, while we are experts in air conditioning brands, and know our Daikins and Grees from our Mitsubishis and Fujitsus, we don’t necessarily have contacts at the inverter manufacturers. Amtech, Danfoss, Vacon and Yaskawa are all names we know, but the local dealer for any of them is probably not in your phone book. This is especially true if the unit you need is from a first-generation inverter driven aircon unit and well over a decade old. While we are experts in air conditioning brands, and know our Daikins and Grees from our Mitsubishis and Fujitsus, we don’t necessarily have contacts at the inverter manufacturers Maintenance techniques While inverter maintenance can be daunting, it isn’t difficult. The tools you will need most often are nothing more than a rag and a spanner, while the more esoteric kit is stuff you probably carry anyway, a laptop, vacuum and a Fluke meter. Before you start, remember that while we tend to refer to an inverter as an inverter, the manufacturers themselves, and many of the sources of information online, often refer to them as VSDs (Variable Speed Drives), VFDs (Variable Frequency Drives) or just plain old drives. As a result, when you are searching online for a video to explain something, it’s worth using all three of those terms, alongside the inverter manufacturer’s name and the problem to make sure you get the right result.While inverter maintenance can be daunting, it isn’t difficult When you do move on to maintenance, step one is simple; make sure that the unit is free of dust. This is as easy as vacuuming the heatsink with an ESD (Electrostatic Discharge) vacuum cleaner when you perform routine maintenance or investigate a problem. While you are checking for build up of dust and daily grime, check the filters. They will probably have to be replaced during annual maintenance, but high use might mean they need to be replaced more often. The control panel itself should be well ventilated and free of dust as well, if it isn’t it can overheat, which is the number one cause of inverter damage and the most common reason contractors contact us for replacement units. Before you put your vacuum and duster away, you should make sure that the inverter unit’s location is clean and as sheltered from the elements as possible. Because it’s normally situated on a roof, it’s not going to be perfect, but the units are designed to take a limited battering. That doesn’t mean it’s okay for them to be covered in leaves, surrounded by rubbish or immediately beneath the guttering outlet though! Before you put your vacuum and duster away, you should make sure that the inverter unit’s location is clean and as sheltered from the elements as possible Get out the spanner Once you’ve finished these steps, you are done with dusting for now, it’s time to get out your screwdriver and your spanner. Step one is to make sure the fans on the inverter are operating normally, without noise and with nothing blocking their rotation. The fan keeps the internal components running effectively, just as it does on PC, and if its function is impaired the capacitors will overheat and the inverter will fail.When you install or maintain an inverter on an air conditioning system, it is a sensible precaution to back up the drive parameters to your laptop The next job is to grab your spanner and make sure the power terminals are on tight. Loose connections cause arcing, overheating and even melting of components and are easily checked during any kind of maintenance and repair. While we are still in the realms of the work your apprentice can do with their eyes closed, you should also make sure that the inverter’s removable LCD control pad is stored sensibly and not continually attached to the drive. If it remains attached, there is a chance the display will stay on permanently, which means that when you need it to diagnose a problem, it will probably already be burnt out. Break out the laptop When you install or maintain an inverter on an air conditioning system, it is a sensible precaution to back up the drive parameters to your laptop. It takes minutes and is normally done by using the removable LCD control. In fact, it’s often as simple as selecting ‘PARs’ and then ‘BACKUP’ from the menu. If you struggle, there are lots of videos on YouTube, like this one, which explain the process for each drive. As a result, if the inverter ever does need replacing, you can whip out your backed up parameters and order a new or refurbished one easily, before reloading the parameters to the replacement and getting up and running in no time. Your customers will think you are a power electronics genius, as well as a HVAC expert, and they will be loyal for life; especially of you save them on a hot day! If you follow these simple measures, you will find that the inverters in your customer’s air conditioning units last much longer and no motors will have to run the equivalent of a cross country, thanks to a lack of inverter control.
Sensors have been used in buildings since the invention of air conditioning to understand how buildings are performing, from in-room temperature sensors, to sensors on plant equipment, motors, ductwork and pipes. The Internet of Things (IoT) has enabled more sensors of different types to be deployed in more locations throughout the building easier than ever before. The point of installing and using IoT sensors is to gain deeper insight into how buildings are performing, and ensure buildings are healthier, more productive for people to work in, more effective to run and more energy efficient. This article looks at in-room sensors, such as temperature, air quality and occupancy, and how IoT sensors can help improve building performance. The benefits of IoT sensors is that they are easy to install, both physically and from a commissioning perspectiveThe benefits of IoT sensors is that they are easy to install, both physically and from a commissioning perspective. Cabling is usually minimal or not required at all: IoT sensors are battery powered, or require simple USB power (from a plug socket) or utilise Power over Ethernet (PoE). IoT sensors use low power wireless protocols (such as Bluetooth, Mesh etc) to send data, and thus can be placed anywhere within a building and do not require multiple physical IOs for integration. Unprecedented amounts of data IoT sensors are usually cost-effective such that thousands of sensors can be deployed throughout the building without much effort. This gives an unprecedented amount of data to building managers, which comes with its own challenges – How to make use of this data? There are two ways to utilise this data to improve building health, performance and efficiency: Use an effective monitoring platform or data analysis tools to turn raw data into actionable insights. This can provide the building and facilities team with insights to be more pro-active, and spot temperature, air quality, overcrowding, etc issues even before the users or tenants begin to notice e.g. it’s too cold, too drafty, too stuffy, etc. Integrate the live data from the IoT sensors straight into the Building Management System (BMS) and create new control strategies to automate the building further. This requires a bit more integration and commissioning work upfront, but the performance and efficiency benefits through automation will give a fast Return on Investment. The key here isn’t the sensor integration itself, but the building control strategy that will be the logic to which the building automation fucntions. Some use cases of IoT sensors are: Temperature and HVAC A common problem I’ve heard from many buildings is that existing temperature sensors that connect to the BMS have been placed in the ceiling, and not at head height. Using battery powered IoT temperature (and humidity) sensors, and sticking them to the wall at head height, is a quick and easy way to measure temperature where it actually matters.Data can be used to plot temperature heatmaps, find hot or cold spots, or analyse the solar heat gain Data can be used to plot temperature heatmaps, find hot or cold spots (e.g. if two nearby FCUs are working against each other, one heating one cooling); or analyse the solar heat gain, and adjust internal loads. The IoT temperature sensors can be connect to the BMS to provide more accurate temperature data to FCUs instead of the sensors in the ceiling. In general, IoT senors can easily be reconfigured and moved, e.g. during a fit out. But care needs to be taken to keep a close eye on the sensors and which room/space they relate to. Battery will need to be changed every 5 years. The IoT temperature sensors are cheap enough that they can simply be replaced with new ones e.g. the sensors element need recalibrating. Indoor air quality sensors and HVAC Accurate CO2 level sensors (which use duel channel NDIR technology) with IoT connectivity are getting cheaper and can also be used to do ‘heatmapping’, of the building, and provide accurate insights on indoor air quality. Similarly, heatmaps can be done with particulate matter sensors (PM10, PM2.5, PM1), VOC sensors and others embedded in an IoT connected sensor. CO2 level sensors in Accurate CO2 level sensors with IoT connectivity are getting cheaper and can also be used to do ‘heatmapping’particular are important as the level of CO2 indoors affects our cognitive ability. High indoor CO2 levels hinder our productivity. Indoor CO2 levels of 900ppm to 1400ppm and higher, which are seen in buildings with poor ventilation, reduce our ability to make decisions and use complex information by 15% to 50% and higher, respectively. Indoor CO2 levels are also a good indication of the risk of infection, as people breathing are usually the main source of CO2 in buildings. So being able to monitor CO2 levels in every space inside the building will provide building owners, tenants and users with reassurance with regard to COVID-19 related challenges. ‘eCO2’, a derivative from VOC sensors, should NEVER be used as a measure of CO2 levels. All CO2 sensors elements need to be recalibrated every 3-5 years. Occupancy level and HVAC Knowing the occupancy on every floor of the building can be used to control HVAC systems. Through BMS integration, controlling the flow of ventilation dynamically, based on real-time floor-by-floor occupancy, allows the building to ‘breathe’ with actual demand.Employing an occupancy-based, dynamic control strategy on the BMS reduces the energy consumption for buildings that rarely see full occupancy This balances the building from a technical perspective, and improves air delivery by opening up more ventilation capacity. Employing an occupancy-based, dynamic control strategy on the BMS, not only improves the indoor air quality, but also reduces the energy consumption for buildings that rarely see full occupancy, or have dynamic use (which will only be more common as we begin to work-from-home more often) Measuring the number of people is difficult, which usually means expensive. One way to count people is using PIR sensors places under each desk. This can get expensive for 1,000 desks even if one IoT PIR sensor is relatively cheap. Another way is to use a less accurate, but cheaper method, e.g. using long-range sensors that count the number wireless devices in a vicinity / floor, and using that as a proxy for percentage occupancy levels. Summary 1,000s of IoT sensors can be easily installed anywhere throughout any building. To get the best out of an IoT system a clear use case (or set of use cases) is necessary. By understanding the use cases and benefits, the right design, UI or integration can be used to maximise the cost-benefit ratio for the specific use cases, for example: BMS integration for IoT temperatures sensors; Relevant platform UI and analysis to extract actionable insights for the Facilities Management team from the raw IoT sensor data; or Correct HVAC control and automation strategy based on occupancy level data.