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Variable Refrigerant Flow Systems (VRF or VRV) - Expert Commentary

Using Silicone To Improve HVAC Insulation & Energy Efficiency
Using Silicone To Improve HVAC Insulation & Energy Efficiency

The modern technological world is filled with ‘extrusions’. They are all around us, in the form of small and not-so-small cross sections. The function of an extrusion is to form seals between components of complex machinery and keep them functional. And, depending on the ‘type’ used, they can make a big difference to how a machine operates. Some of the most desirable types of extrusion — and especially for use in HVAC systems — are those made from silicone. Silicone, which is a type of rubber, has a robust set of properties. For one, silicone can withstand extreme temperatures, both high and low. Semi-Exterior environments Ranging from -60°C to temperatures exceeding 200°C. (And there are even higher grades that can be manufactured to withstand temperatures well above 200°C.) Ideal for HVAC units that work round the clock to keep large numbers of people in large buildings comfortable in summer and winter conditions. In addition to this, silicone is also one of the more resistant properties to the constant vibrations of working machinery. It can be difficult to locate the source of the problem if a tiny extrusion has dislodged. Vibration-resistant properties make silicone extrusions less likely to disengage or fall out of place, therefore minimizing the need for costly repairs. Finally, silicone is also more durable than most other materials when it comes to exterior or semi-exterior environments, such as that of rain or ultraviolet light. Protecting electrical components Silicone is useful in HVAC systems because it offers enhanced sealing and compression protections As a result of this favorability, there is already a considerable number of different types of silicone extrusions that can be found in a lot of HVAC systems. These include HVAC sealing gaskets, hatch seals and vibration isolation pads. But also silicone sponges, which act as a protective layer of thermal insulation. As well as providing thermal insulation, silicone sponges can double-up as a form of acoustic insulation, with considerable noise reduction and anti-squeal properties. Silicone enclosure gaskets protect electrical components, and environmental seals — as the name suggests — help to keep everything protected from the sometimes harsh elements of the environment outside. Silicone is useful in HVAC systems because it offers enhanced sealing and compression protections over most other materials. Closed cell structure On a material level, silicone has a ‘closed cell structure’, which helps to keep out moisture ingress, along with water and dust. The combination of a closed cell structure, along with sealing and compression benefits, makes silicone ideal for exterior seals and gaskets in and around HVAC systems. The softer grades of Silicone have an excellent memory and low stress relaxation, which in turn helps to prevent common faults with HVAC systems — usually caused by gasket failures made from other materials that soften and compress inaccurately. The low stress relaxation properties require minimal force on behalf of the engineers sealing the enclosures, while the memory-properties of the silicone allow it to conform to awkward shapes and gaps of various widths. Manufacturing HVAC systems proactively with silicone in mind can allow more design flexibility on behalf of the engineers. Inevitable rapid movements General purpose solid silicone or silicone sponge is suitable for many HVAC applications And, as mentioned above, vibration isolation pads work as dampers to protect against the inevitable rapid movements of the systems as they power along. But also to help withstand the vibrations of HVAC units on transport systems, such as buses and trains, which naturally vibrate as they run over imperfections on rail and road tracks. As it happens, general purpose solid silicone or silicone sponge is suitable for many HVAC applications, not just those discussed above. The designs of the extrusions would be different, reflective of their function, but the material would be the same. In some instances, customers may also require a flame retardant silicone — certified to UL94 specifications — in order to meet safety standards in certain situations or environments. Great temperature ranges For all its material advantages, silicone is generally more expensive than the other types of material rubber that are used to manufacture extrusions, such as ethylene propylene diene monomer (EPDM). And while other materials do of course have stand-out benefits of their own — EPDM for example is more hard-wearing than silicone — silicone is still often the extrusion ‘type’ of choice because of its ability to withstand great temperature ranges. This is very important for heating and air conditioning systems. Because some of the most common factors that cause HVAC systems to break down are as a result of seal and gasket failure, which can come about as a result of an overheating unit. Very cold environment Chances of a unit overheating can be just as likely — in fact perhaps more so — where the system has to operate in a very cold environment. With the threat of climate change etched more than ever into the public discussion, we can predict that there will be a steady increase in the amount that this material is used to make up the HVAC seals. And not just because, as temperatures continue to increase and summers get hotter and more prolonged, there will be an increased demand for them. Effective public relations It is no secret that HVAC systems can be relatively expensive to run It will become a matter of effective public relations for managers, building regulators and transport officers to make sure that the equipment they are using — and making — is ‘green’. By using the right materials that help conserve energy and increase efficiency, this will not only sit right with the general public, it should also be more economical, too. It is no secret that HVAC systems can be relatively expensive to run. Minimizing wastage, and the time spent on call outs and repairs will make a notable difference. Of course there are many other ways to also set about making air conditioning and heating units more efficient. Using seals or gaskets made from silicone is just one small piece of the puzzle. But utilizing them will almost certainly be more beneficial than you might imagine. And anything that is a step in the right direction is a welcome change.

VRF Systems and Cold-Climate Applications
VRF Systems and Cold-Climate Applications

Building owners and specifiers can experience design flexibility, reduced operational costs and reliable, energy-efficient comfort year-round with Variable Refrigerant Flow (VRF) systems, even in extreme cold climates. Modern VRF systems like those from Mitsubishi Electric Trane HVAC US far exceed the capabilities of conventional heat pumps at low outdoor ambient temperatures and are in a great position to replace fossil fuel burning equipment in almost any climate. The Fundamentals of VRF Systems VRF technology consolidates heating and cooling into one VRF technology consolidates heating and cooling into one, all-electric system. Improving on the direct-expansion (DX) principle, a VRF system uses linear expansion valves (LEV) and an INVERTER-driven compressor to cycle refrigerant and transfer heat between its outdoor unit and the indoor unit(s) in each zone. Continuous communication between the system’s outdoor units, indoor units, sensors and controls allow VRF systems to modulate capacity based on loads and occupancy. With precise management of capacity, VRF systems reliably maintain each zone’s set point without the noisy and energy-intensive start/stop cycles of conventional systems. Design Considerations for Low-Ambient Heating The reliable performance and energy efficiency of modern VRF systems aren’t solely the product of superior product engineering. Accurate load calculations, proper installation, diligent commissioning, and regular maintenance, are essential for success. Let’s discuss six options HVAC contractors and engineers can use to solve derating challenges, even in climate zones 5 and 6. HVAC contractors can solve challenges, even in extreme climate zones Options for Solving Derating Challenges  With VRF flash-injection technology, as long as an air-source heat pump can make its refrigerant cooler than the outdoor air, thermal energy can be extracted and delivered to interior zones as heat. In extreme cold, the compressor needs to operate at speeds much higher than usual to drive the refrigerant temperature and pressure in the condenser coil sufficiently low to capture ambient heat. With flash-injection technology, a VRF system injects a small amount of mixed-phase refrigerant to cool the compressor, allowing it to perform at higher speeds without failing due to friction and heat build-up. This method enables VRF systems to deliver significant heat at low temperatures. For example, CITY MULTI® VRF systems with Hyper-Heating INVERTER® (H2i®) technology can provide up to 100 percent of heating capacity down to -4° F, up to 70 percent of heating capacity down to -22° F and continuous heating at temperatures as low as -31° F. Flash-injection technology creates the opportunity to size units based upon heating loads and use the VRF system as a sole source for heating. In most regions, changeover to auxiliary heating sources is rarely needed, but can be easily accomplished with built in controls if an existing heating system is already in place. Auxiliary or backup heat can be provided by a system that generates heat using a method such as electric resistance, baseboard hydronic wall-fin radiant heat or duct coils mounted downstream of an air handler. Auxilliary or back-up heat may be installed with the VRF system while others might be an older existing system, such as a gas-fired hydronic boiler a facility repurposes after a retrofit. Due to greater efficiency, the VRF system typically provides the first stage of heat. Sole-source sizing based on heating is an alternative to using a flash-injection product, employing the option to oversize standard VRF systems for heating capacity. Specifiers must be mindful of heating derates as found in the VRF manufacturer’s selection software or engineering manuals when using this method. Designers will likely need to oversize the indoor units as well as the outdoor unit. Otherwise, the indoor units will be unable to use the extra capacity. Oversizing VRF systems to meet heating capacity should be limited to 25 percent or less so that the system doesn’t end up being excessively oversized for the commensurate cooling load. Oversize DOAS heat. VRF systems are often used in conjunction with complementary systems for ventilation. A dedicated outdoor air system (DOAS) is typically designed to supply room-neutral air (between 70° F and 75° F) in the heating mode but could be upsized to provide additional heat. With the use of a recirculation air damper and an upsized heat source (gas, hot water or electric), the oversized DOAS could be used for emergency heat or morning warmup during winter. Install outdoor units inside the building to limit derating and weather impacts in severe cold regions. In this scenario, air-source condensers are installed in a mechanical room that serves as a recirculation air plenum or a pass-through air plenum, depending on the outdoor temperature. When the auxiliary heat runs, the VRF system’s efficiency approaches the efficiency of the backup system. If the unit heater is 80% efficient, the overall system efficiency will drop so the backup unit heaters that heat the mechanical room should only run at colder temperatures. While this approach can be expensive due to the number of dampers and louvers required, the design allows a facility to locate auxiliary heat in a central location, the mechanical room. Water-source VRF systems are available as heat pumps or with heat recovery. With water-source VRF systems, all of the equipment is designed to be installed indoors. They deliver greater efficiency and have less derating versus air-source VRF systems. Less energy is needed to extract heat or reject heat into or out of water, as compared to air due to the density of each of these mediums. Also, a water loop offers a more defined and controlled temperature range, generally between 60° F and 90° F. The capacity of a water-source system is based on entering water temperature. VRF Systems Provide Comfort in Any Climate When applied according to best practices and with consideration for winter weather, modern VRF systems can serve as the primary heating and cooling system even in the coldest climates. With flash-injection compressor technology and water-source options, VRF systems offer cold-climate capabilities far beyond those of conventional heat pump systems, even without auxiliary heat. 

HVAC Recruitment Considerations In 2020
HVAC Recruitment Considerations In 2020

As a Managing Director of a company that provides temperature and humidity solutions to predominantly the warehousing and industrial sectors, I thought I would share my dilemma that I’m sure other business owners and managers also face. I don’t pretend to know the answers, but thought it might be worth sharing some of the considerations that I’m facing in whether to reshape, recruit and build or hunker down until the World, Europe and the UK offers some sort or predictability. I promise to not refer to ‘new normal’, masks or social distancing as this is extensively covered elsewhere. Context Our business has seen steady growth in the past 5 years, as a result of our efforts to create and retain relationships with customers who value our offer. Our focus has always been to offer solutions to large scale complex HVAC projects. We invest heavily in intellectual talent sponsoring PhD and MSc students, to keep us on our toes and develop leading edge solutions. We also feed off each other and our network of equally talented suppliers. My dilemma as Managing Director is do I continue our ambitious Research & Development (R&D), IP and Business Development or throttle back and take a cautionary approach until the economy offers a more certain platform? ‘Fortune favors the brave’ they say, but when you have a good business and employees look to business managers to ensure their livelihoods, how brave is brave? The Dilemma Immediate transactional or contractor resources are easy to obtain with the right screening and due diligence Immediate transactional or contractor resources are relatively easy to obtain with the right screening and due diligence, but for more developmental strategic roles, do you recruit in an emerging post pandemic, catastrophic employment forecast, that to in a mid/post Brexit world? From my personal perspective, it boils down to attitude, communication, enthusiasm and buy-in from everyone in the company. Nothing new there, but it feels that the stakes are higher so confidence is key. Do we or don’t we? Inaction is the riskiest response to the uncertainties of an economic crisis. Rash or scattershot action can be nearly as damaging. Rising anxiety (How much worse are things likely to get? and for how long is this going to last?) and the growing pressure to do something often produces a variety of moves that target the wrong problem or overshoot the right one. Within the world of HVAC, changes to legislation, environmental considerations, technological changes and research and development might be slowed or influenced, but won’t stop as a consequence of the immediate economy, which is a good thing. Recruiting on a need basis Many companies recruit when needed, to fill a vacant position or when a large project demands more manpower than the current headcount supports. This approach is obvious and addresses immediate transactional and resource needs. Using headcount as a KPI for growth, at a glimpse may illustrate positivity, but may be signaling a stop gap and may not be a true indicator of strategic growth. Of all the things I have observed over the last 5 months, reading the news, talking to colleagues and peers, a few things have stuck out for me, such as how companies have treated their employees, customers and suppliers, how creative and flexible some big organizations have been in responding to market changes and demands and how, despite uncertainty, their core business skills, intelligence and ability enabled them to prosper in a new and unforeseen environment. Finally, how companies will be remembered post crisis. Robust business planning The ability to respond quickly to market changes relies on creativity and attitude My belief is that those companies that have and continue to float to the top had the key ingredients of a successful business, enabled by capable enthusiastic talent that were given the opportunity to shine. These people weren’t hired to fill a stop gap, but rather these people were hired as part of a robust business plan. So, ‘do we or don’t we?’ Our philosophy at Jet Environmental Systems is to have a solid platform, identify future markets, trends and technologies and hire the absolute best people that we can to get us there. Recruitment in our business is a process that supports our strategic development and so for us our answer is yes, have confidence and continue to invest in the best talent. The ability to respond quickly to market changes relies on creativity and attitude with support from equally enthusiastic management who create the opportunity for individuals who present this talent to grow. Conclusion I hope the thought process I’ve shared has been useful, for me it has been a checkpoint in whether our choice of investment in people is right, not just now but in all situations. For me, it’s a resounding yes! I think we will create opportunities by having vision and giving people opportunity.

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