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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.
It is said that the COVID-19 pandemic has been one of the single biggest driving forces behind the digitalization of industries ever seen. And although not new within HVAC infrastructures – especially within the food retail environment where it has been rolled out extensively – remote management and automation of HVAC systems is increasingly being used to support supermarket responses to COVID-19. From air filtration through to dynamic scheduling, digitalization of HVAC within the food retail sector is going through something of a renaissance. Pre-COVID Digitalization Software solutions that use Internet of Things (IoT) technology to analyze data from HVAC infrastructures, for example, are common in food retail stores. These solutions work by monitoring mission critical aspects of HVAC systems, from simple temperature data through to complex asset monitoring. This data can then either be fed back to the retailer for them to perform their own analysis or, using more advanced IoT technology, can be used to enact automated HVAC outcomes. Software solutions that use IoT technology to analyze data from HVAC infrastructures are common in food retail stores From preventing HVAC asset’s overworking – and therefore expending too much energy – through to detecting the first stages of a fault and alerting the relevant maintenance engineers, automation has been shown to deliver numerous benefits. These combine to serve the retailer’s primary purposes; enhancing the consumers in-store experience, improving the bottom line and decreasing energy usage to lower carbon footprint. But not only is the digitalization of HVAC helping food retailers drive down costs and energy, advances in areas such as air filtration and dynamic scheduling have meant that it is also being seen as a potential solution to COVID-19 related issues. Filtering Out the Virus Air filtration is a primary focus when looking for ways to keep internal spaces free from pathogens. While not exactly a new feature for HVAC systems, food retailers have been increasingly working towards implementing or improving their existing air filtration techniques in their stores. The solution to keeping air clean and fresh is actually quite straightforward and relies on the same technology that many stores already use to monitor CO2. Advances in areas such as air filtration and dynamic scheduling have meant that HVAC is being seen as a potential solution to COVID-19 By connecting CO2 monitors to a central controls panel (the technical way of describing the place where all of the sensor data is collected and, in some cases, analyzed), sensors are able to detect the CO2 levels instore, signal if they begin to drift past a pre-determined base level, and automatically alert the HVAC systems to provide more fresh air into the store. This is a simple process of optimization. Additional sensors detect when fresh air is either too humid, hot or cold to be filtered into the store and rectify this by automatically adjusting the HVAC. Essentially, monitoring CO2 and air quality levels makes sure the air in a store is constantly fresh and filtered to keep the chances of airborne transmission as low as possible without causing the HVAC systems to expend any more energy than is necessary. Research has shown that COVID-19 spreads through small respiratory droplets that are released into the air from an infected person when coughing, talking or even breathing. Within a store environment therefore, where surface contamination and proximity to other people are likely to increase the chances of transmitting the virus, optimized fresh air flow to dilute indoor air is desirable. By detecting higher levels of CO2 within the air which in turn increases the chances of pathogens floating around, food retailers can automate their HVAC systems to filtrate the air and significantly reduce chances of transmission. Dynamic HVAC Response Air filtration isn’t the only way that food retailers are combining digitalization and HVAC systems to help them navigate the ‘new normal’. With store opening times continually changing, fewer people inside a store at any one time and staff performing additional and stricter clean regimes after hours, the requirements for optimum store temperature have moved from static to dynamic. Before the pandemic, HVAC systems would have to keep an average non-24 hour store at the optimum temperature for between say, 7am and 11pm, and would have to work a little harder to deliver more air into the store during the lunch time rush and post-work peaks – a mostly predictable routine. Research has shown that COVID-19 spreads through small respiratory droplets that are released into the air from an infected person Now, however, with adjusted store schedules and social distancing regulations, the footfall and peak traffic times have changed dramatically. Through digitally enabled remote management of HVAC temperatures and schedules, new schedules could be deployed across the estate at the touch of a button. Real-time monitoring of in-store temperatures and the volume of people inside also enables HVAC systems to run more efficiently by stopping them from filtering in more outside air than is necessary in a shop that contains fewer customers than normal. IoT solutions are ensuring HVAC infrastructures are running efficiently, saving energy, helping a retailer’s bottom line and most importantly, ensuring the comfort and safety of customers and colleagues. However, as retailers look for solutions to the challenges posed by the post-COVID landscape, digitalized HVAC is breathing fresh air into the industry. From improved air filtration to dynamic schedule monitoring, digitalized HVAC systems are proving to be an important tool in a food retailer’s arsenal as they navigate the new normal.
Effective heating, ventilation and air conditioning systems have always been part of maintaining a healthy building environment, and with the impact of COVID-19 and the unique way the virus is spread, it has never been more imperative that HVAC plays a vital role in keeping occupants of buildings safe, especially as people begin to return to the office and other commercial environments. COVID-19 has three known contamination routes. First of all, there is person-to-person transmission, which could be indirect too, if the virus travels from someone to a surface they have touched, which is then touched by another person. Then there is airborne transmission. The British Council for Offices (BCO)’s Thoughts on Office Design and Operation After COVID 19 document talks of large droplets, greater than 10 micrometres, “expelled by sneezing and coughing and in still air, typically within about 2 metres of the infected person.” But Dr Linsey Marr, the Charles P. Lunsford Professor of Civil and Environmental Engineering at Virginia Tech, speaking to the New Scientist says that people emit thousands of times more smaller droplets than larger ones. She thinks that it is these ones that infect people with COVID-19. Then there’s the third contamination route: faecal to oral whereby particles from the toilet can enter people’s respiritory systems when using WCs. Counteracting COVID-19 transmission There are several methods to counteract these routes of transmission. The risk of the virus spreading from person-to-person can be lessened where there is a focus on smart technology. This begins upon arrival at a building, with the use of touchless entry systems, for instance harnessing facial recognition technology. Once inside, staff could then be directed to an area of the office that isn’t already occupied via digital signage or an app. And instead of manually pressing a button, information from the employee’s ID pass about which floor they work on can be read by a card reader, activating the elevator. As for transmissions via surfaces, scientists have emphasized copper’s antibacterial properties, with COVID-19 surviving just a few hours on copper, compared with a number of days for steel or plastic. William Keevil, a senior microbiologist at the University of Southampton, has recently suggested that the UK is behind other countries in using this material on communal areas like handrails and doorknobs. Copper-based nickel would perform better than chrome in certain parts of the office too. The risk of the virus spreading from person-to-person can be lessened where there is a focus on smart technology To dilute airborne contamination, the Chartered Institute of Building Service Engineers (CIBSE) recommends running ventilation systems at a higher flow rate. “This may require changes to C02 set points for both mechanical ventilation and automated windows,” it states in its COVID-19 Ventilation Guidance. Airborne Particles and the need for ventilation Chinese and American academics looking at outbreaks in the Chinese province of Zhejiang found that airborne transmission of the virus may have taken place in 48.3% of people in a badly ventilated office. Essentially to stop the spread of COVID-19, ventilation needs to be increased and more fresh air needs to be brought in. The risk of contamination via recirculated air can be mitigated with a higher level of filtration such as F9. This is a very fine system that will catch nanoparticles of 70nm but does involve greater energy use to overcome the resistance. The alternative is to keep these systems on for much longer – typically two hours before people arrive and then two hours after they leave. CIBSE’s COVID-19 report also states that, “Recirculation of air within a single room, where this is complemented by an outdoor air supply, is acceptable.” Getting abundant fresh air in the system is key. This could be as simple as just opening the windows. The BCO’s report goes so far as to say, “Actively use operable windows and openings to boost ventilation to occupied spaces as much as possible, even if this is at the expense of thermal comfort.” Fan coils and Chilled beams Getting abundant fresh air in the system is key The BCO also recommends that fan coils, which recirculate air locally in the occupied space, “should be frequently and thoroughly cleaned and where condensation occurs, drain pans and traps should be maintained frequently to prevent growth of bacteria and mold.” It is also a recommendation that HepVo traps are installed on condensate systems that drain into waste pipework. As far as chilled beams are concerned, CIBSE says that active chilled beams can be operated as normal, while with passive chilled beams there should be a good supply of air. I would be interested to see some further research on the performance of underfloor and low level air distribution. The lower velocities and laminar air flow associated with these systems causes less air turbulence, particularly in the zone where air is breathed. This would seem to have an obvious advantage in reducing the risk of virus spread in an office environment. Mixed Mode Ventilation The ‘mixed mode’ of ventilation will become more commonplace. When it is not high summer, the cooling can be turned off so windows can be opened. This could even eventually replace the familiar sealed building model. This system can happen automatically with sensors, after all, fresh air is good for people: There are several recent examples of this being done successfully, other building such as London Wall Place, have been designed future proofed for ‘mixed mode’ use to be adopted if this is preferred by a tenant. Meanwhile, to combat faecal-oral transmission, bathroom extraction fans need to be kept on high and again perhaps running the systems for 24 hours a day. Toilets that automatically shut and touchless flushes can also help to stop the spread of the virus. The same goes for anti-bacterial coatings on bathroom doors. Some of clients are considering motorized doors that are effectively ‘touch free’. Post-COVID Ventilation Strategies Toilets that automatically shut and touchless flushes can also help to stop the spread of the virus There is definitely set to be more access to outside air moving forward and there is a strong sustainability argument to be made for this method. However, some of the changes to ventilation strategies being deployed for a post-COVID world will inevitably have some compromises for carbon emissions. If systems are run at a higher rate and for longer, if not continuously, throughout the day then that has implications for a larger carbon footprint, as the buildings become less energy efficient. However, in the middle of a global pandemic, it’s a price worth paying. As energy saving methods (thermal wheels and plate heat exchangers) also present a risk, CIBSE recommends that these are bypassed and not used in the current environment Of course, some of these solutions are temporary but other, smart office elements like touchless versions of door handles, room/desk booking systems (wayfinding) and reception sign-in procedures look set to be with us for the longer term. These all affect the M&E, as well as the architecture and design of buildings. We will overcome COVID-19 but we need to listen to the lessons that we are learning, and some will most certainly become permanent before the next virus that hits the human race comes along!