When it comes to choosing a new HVAC system, building owners and managers have many options to choose from, including traditional rooftop units, boilers, chillers, variable refrigerant flow (VRF) technologies, geothermal systems, and more. Some may even opt for a combination of technologies they believe will best serve their comfort and energy-efficiency needs.
Each system type comes with its own unique set of benefits, and as long as building owners and managers remain open minded, they may be surprised at the possibilities now available.
THE EMERGENCE OF VRF
VRF systems have become very popular in the commercial market and are expected to gain even more market share in the coming years.
“It’s a technology that’s grown significantly, and we estimate it comprises somewhere around 6 percent of the total commercial HVAC market today,” said Kevin Miskewicz, senior marketing manager, commercial products, Mitsubishi Electric US Cooling and Heating Division. “We expect to see that grow to 9-10 percent over the next couple of years.”
Considering that the first VRF systems were installed in the U.S. a little more than a decade ago, their acceptance in the market has come very quickly. The reasons for their growing popularity include energy efficiency, which is achieved through the use of components such as inverter-driven compressors, and the fact that they can be installed in just about any type of building.
“The biggest misconception about VRF systems is that they can’t be used in big buildings, but that’s not true,” said Miskewicz. “The technology is extremely flexible and can be used in everything from a large single-family home all the way up to a 40- or 50-plus-story building. The only limitation is vertical separation, as outdoor units cannot be installed thousands of feet away from indoor units.”
VRF systems can usually provide 100 percent of a building’s cooling and heating needs, although backup heat may be necessary in climates that experience bitter cold. Thanks to advancements in technology, Mitsubishi Electric’s Hyper-heating Inverter™ VRF system, for example, can perform at 100 percent of its rated heating capacity down to minus 4°F outdoor ambient, and if temperatures get down to the minus 13°F range, it can perform at about 85 percent of capacity. “That means, for the vast majority of applications in the country, a VRF system can handle 100 percent of a building’s heating and cooling needs,” said Miskewicz.
The initial installation costs may seem a bit steep, but if overall costs are taken into account, VRF systems can be less expensive in the long run, said Miskewicz. “With VRF, there is savings in both installation labor and materials costs, because, first of all, refrigerant piping is used instead of ductwork. Second, VRF units are smaller and lighter, and even the largest units can fit in a freight elevator. The need for additional structural supports on the roof is eliminated, and there is no need for cranes to put them in place. Third, the electrical loads of a VRF system are usually minimal. Finally, VRF systems typically run for 20-25 years, which is longer than most rooftop units, which usually only last 10-15 years.”
One potential limitation of VRF systems is that they can only be monitored — not fully controlled — by most building automation systems (BAS). That is because personal comfort control happens locally in the space, which is where a VRF’s zone controllers are located. “This is a gap we recognized, which is why we introduced our own BAS controller that can manage and operate our VRF system, as well as virtually any other mechanical system within the building,” said Miskewicz. “Our software is built on Niagara’s Tridium framework, so anybody can service it. It’s not proprietary to our technology.”
VRF systems may also not be the best option in applications that require significant amounts of outside air along with frequent fresh-air changes, such as operating rooms and cleanrooms, said Miskewicz, though, aside from that, they’re well-suited for virtually any application on the market.
GOING TO GROUND
For more than 20 years, building owners and managers have had the ability to choose a commercial, ground-coupled, water-source heat pump system (GLHP) to heat and cool their facilities. Many are taking advantage of this technology, as GLHPs offer low operating costs as well as numerous other benefits, said Alan Niles, Western region commercial sales manager, WaterFurnace Intl. Inc. “In addition to the operating cost savings, GLHP systems will enhance a zero-net-energy building design by providing heat recovery throughout the building for non-HVAC systems — refrigeration cases and freezer cases, ice making machines, domestic hot water systems, etc. — as well as the HVAC system.”
In addition, the GLHP system can provide a path of compliance for many new building codes. For example, without the need for outdoor components such as cooling towers there is significantly reduced loss of potable water, which has become a code requirement in many states. “By eliminating the outdoor equipment, the GLHP system also eliminates the noise to the surrounding environment, which is becoming a code issue,” said Niles. “Eliminating outdoor equipment also results in less maintenance and reduced construction costs, as there is no need for additional supports for heavy roof-mounted loads.”
GLHP systems can also be installed with other types of HVAC technologies in order to create a system specifically tailored for a building’s needs. “Hybrid GLHP systems are more popular than ever,” said Niles. “While some portions of the building can be served by traditional water-to-air heat pumps, other areas can be served by connecting directly to a common water loop. For instance, adding modular heat recovery chillers to the loop can provide chilled water to chilled beams for libraries, fan coils, and custom air handlers as well as provide hot water for radiant floor systems for loading docks and makeup air systems.”
Some may believe the initial cost of a GLHP system is significantly higher than other HVAC technologies, but that is really not true anymore, said Niles. “As hybrid designs become more sophisticated, the first cost of the ground loop is quickly becoming a non-issue. In the past 10 years, with increased efficiencies of the equipment and simply enforcing better design techniques of the ground loop and better bidding practices, the size and the cost of ground loops have been reduced by 30 percent. Adding a hybrid design can drop that first cost by another 30 percent.”
While GLHP systems can work well in just about any application or climate, they do have some limitations, including the need for sufficient land area. “This can limit the application of GLHP systems for inner-city buildings that are situated on small lots of property,” said Niles. “In addition, some local geological formations may make the installation of the GLHP uneconomical, and in areas where the market is not well developed, finding qualified designers and installers can be a barrier.”
Still, GLHP systems make sense for the vast majority of buildings, said Niles, thanks to the laws of thermodynamics. “Cooling and heating a building requires moving heat. Air can move heat in short distances, but as the conditioned space increases, the costs for additional fan power and ductwork, combined with increases in duct losses, reduce system efficiency. Refrigerant can also move heat short distances, but as the system becomes larger, the compressor uses more energy to pump the refrigerant, which quickly drops a system’s efficiency. Water moves energy much more efficiently than air and is easily scalable to larger conditioned space, which makes the GLHP system an excellent choice for just about any project.”
THE WONDER OF WATER
Mark Handzel, vice president of product regulatory affairs and director of HVAC commercial buildings, Xylem Inc. – Applied Water Systems, agrees that water is the most efficient conductor of heating or cooling due to its thermal conductivity, high heat capacity, and ability to store energy. “Hydronic systems provide water-based heating and cooling through pipes and other components, such as pumps, drives, controls, heat exchangers, and valves, that deliver heated or cooled air via an air-handling unit through ductwork and air terminals. These systems offer excellent indoor comfort, lower energy costs compared to other types of systems, and improved indoor air quality.”
Hydronic systems offer a plethora of other benefits, as well, noted Handzel, including:
• Greater reliability because they are less affected by changes in the outdoor air temperature;
• Lower first costs than some systems;
• Improved efficiency through the use of remote monitoring;
• Safety, because water running through pipes won’t release hazardous chemicals into a room if a leak occurs; and
• Increased flexibility to provide multiple temperature zones, particularly in larger buildings.
Hydronic systems can also be paired with other HVAC equipment to form hybrid systems that can effectively meet the requirements for larger buildings or campuses that often have diverse heating and cooling needs.
“In a geothermal system, for example, heating and cooling can be delivered radiantly, through a hydronic system, or through ductwork,” said Handzel. “Radiant hydronic heating systems can also be paired with other systems, such as furnaces, for a dual heating solution. In large spaces, such as a convention center, chilled beam systems can effectively cool at lower costs than air systems.”
Another benefit to utilizing a hydronic system is that most, if not all, of the equipment that make up a hydronic system is engineered to talk to a BAS, including pumps, boilers, and fan coils.
“Communications systems are generally standardized to communicate using the BACnet protocol,” said Handzel. “Enhanced communications capabilities are improving the efficiency of products, from circulators to the overall system. State-of-the-art hydraulics, advanced motor designs, intelligent controls, and smart communication capabilities mean these pumps can do a better job while doing on-the-spot monitoring for instantaneous responsiveness.”
While hydronic systems perform well in new construction or retrofit applications in all geographic regions, they are better suited to handle buildings that require 50-100 ton of cooling capacity or more, said Handzel. “They have the capacity to pump water efficiently and effectively very long distances, such as across a sprawling campus or in high-rise buildings, such as hotels or health care facilities. In addition, they are extremely reliable, providing hot water 24/7 for hospitals, hotels, and other facilities in which reliability is imperative.”
Hydronic systems also last a long time — anywhere from 20 to 25 years — and the initial cost of the system is generally low while offering a wide range of flexibility for components, operation, and maintenance, in terms of both parts and service, added Handzel. “VRF retrofits, for example, can be complicated to update, because all of the refrigerant piping must be removed and replaced floor by floor, which can be an expensive proposition. Hydronic water systems are designed with universal components that can be installed and serviced by any HVAC service technician.”
As can be seen, there are many options available that can satisfy a building’s heating and cooling needs. By working closely with their design engineers and installing contractors, building owners and managers are sure to find the best HVAC system(s) that will meet their requirements.
Publication date: 5/2/2016