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Today’s commercial building equipment and systems, including heang, venlaon and air condioning (HVAC) systems, are becoming smarter and more integrated to help maximise long term performance and value. Building owners and facility managers are constantly on the lookout for new and more eecve tools to reduce repair costs, minimise downme and keep the operang environment in their buildings in opmum condion, as Loc Tieu, global product manager for Southco, explains...


HEATING & VENTILATION


performance. In turn, HVAC equipment manufacturers have been improving HVAC enclosure designs to be more energy- efficient. Enclosures designed with thicker doors and panels help to eliminate leakage and enable the unit to handle the heating/cooling load without excess energy demands. These enclosures are not perfectly sealed boxes, however. They include doors and removable panels, in some cases quite large, for maintenance and repair access and other activities. Changing designs and physical dimensions of these doors call for new latching and hinging technology. Compression latches and hinging technology can improve access to these enclosures and help HVAC equipment suppliers satisfy their end- use customers.


Engineering HVAC energy efficiency


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HVAC units are as essenal to our modern world as data centres, cell phone towers and switching equipment


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HVAC units are as essential to our modern world as data centres, cell phone towers and switching equipment. All are examples of ‘backbone’ systems we employ to make the modern world work. In the case of commercial HVAC units, they keep our workplaces, retailers, hospitals, schools, travel terminals and myriad other locations comfortable and supplied with fresh air whenever in use. These systems share several other characteristics: they use expensive, high-technology equipment that typically operates for long periods of time, for many building environments, HVAC units run 24/7. HVAC systems are heating/cooling vast volumes of air to precisely controlled temperatures and then moving that air continuously, making them major energy consumers. According to US Department of Energy studies of commercial buildings, HVAC equipment typically accounts for over 40 per cent of a building’s energy usage.


For building owners and facilities managers, improving the energy efficiency of their HVAC systems plays an important role in controlling costs and improving margins. That means they will be looking to HVAC systems suppliers who are improving the efficiency of their systems.


To accomplish this goal, HVAC OEMs are creating new enclosures that use heavier metal panels with improved insulation. This design update reduces energy loss from two kinds of air leakage: infiltration and exfiltration. Infiltration is leakage of unconditioned air into the HVAC unit from outside the enclosure. Exfiltration is leakage of air, typically conditioned air, from inside


24 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JANUARY 2019


Access all areas: C


ommercial HVAC units for instance, are demanding more cost-effective and cost-efficient equipment


the unit through the casing to the outside. Both types of leakage increase the amount of energy required to supply conditioned air to the space.


Enclosure access doors are one of the key areas where leakage can develop. Many standard enclosures have been constructed with single-skin wall panels and single-layer doors, with a layer of fiberglass insulation adhered to the panels. These tend to be more flexible, expanding and contracting with the on-off cycles of the air handling units. This flexing, over time, can lead to fatigue on the panel seams, and also affects the seams where access panel doors meet the enclosure walls.


Newer generation access doors are typically double walled and insulated, with the total thickness of the door ranging from 40 to 60mm. These double-panel doors are typically constructed of two separate panels with a thick layer of foam insulation between the panels. Depending on the door size, they can typically weigh between 35 to 50 pounds.


Some doors are just standard panels that open to allow access to control equipment; others are full, man-size doors that enable personnel to enter the enclosure. There are even some very large panels, designed to be removable, that facilitate access to large pieces of equipment inside. Using a heavier access door in these applications increases a high perception of quality and creates an important competitive value for HVAC system providers.


Securing larger doors


The incorporation of larger, heavier enclosure doors calls for different latching and access control solutions. If not properly equipped, doors can become weak points in the enclosure envelope.


Regardless of size, the door still needs to close securely in order to create a near-airtight seal to prevent leakage. Insulated doors typically have a layer of closed cell foam material applied around the door opening, which functions as a gasket to create a secure seal. While standard latching mechanisms were used to secure older enclosures with single sheet metal doors, newer double-skin doors require a different type of latching solution capable of securing a door panel up to 60mm thick. The best solution for this type of door is a compression latch, which holds a panel or cover closed by using a cam action and, at the same time, compresses a gasket around the inside of the door to seal it.


While a compression latch is the right solution for a double-walled door panel with insulation, improper installation of the latch could squeeze the insulation too much, damaging the foam and creating a void that could reduce the insulating factor.


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There are speciality cam latches designed to avoid this problem that can be rigidly mounted to the door with a sleeve and firmly attached to the door without squeezing the foam insulation when closed.


In some cases, these doors have very large dimensions, so a single latch may not be sufficient to fully secure the door. Multi-point latching systems, which allow multiple latch points at the top, bottom and middle of the door to be controlled by one actuator, can provide a simplified access solution for oversized doors.


Intuitive enclosure access


Like latches, hinges are an essential access component in the overall design of the HVAC enclosure, but they go beyond simply joining the panel to the frame. While relatively simple in terms of functionality, the technical capabilities of the latest hinge technology provide design engineers with new options for enhancing the performance of and interaction with panel doors. It’s often the case that when maintenance technicians open an enclosure door, they want it to stay open while they access and work on a control panel or carry out equipment maintenance. Rather than attach an external secondary door stay to prop the door open, detent hinges allow a door to open to a pre-set angle and click into position.


Constant torque hinges fulfil the


uHVAC enclosure designers ulmately need to select the appropriate latching and hinging soluons that will sasfy basic funconal requirements


Improving commercial HVAC efficiency and performance with engineered access solutions


uIn certain HVAC systems, large doors may also need to be easily removed to accommodate the replacement or upgrade of large equipment


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