Here in Texas, where we experience both blistering summers and the occasional freezing winter, we traditionally use HVAC split systems where the condenser and compressor are in an outdoor cabinet connected via a line set to an indoor cabinet, which holds the evaporator coil, with an air handler sending the cool air through the duct system. The traditional central air conditioner/furnace setup places the cooling coil on top of the furnace and utilizes the furnace’s blower as the air handler for the air conditioning system.
Annual Fuel Utilization Efficiency (AFUE) ratings are used to compare the efficiency of gas furnaces. For example, the highest AFUE rating of 99% means the furnace converts almost every bit of the energy it uses into heating the home. Air conditioners are compared by Seasonal Energy Efficiency Ratio (SEER) ratings. The average cooling output of a system is divided by the average energy the unit consumes in terms of watts per hour over a cooling season. In 2023, the minimum rating for the southern U.S. will be 15 SEER, but the most efficient split system on the market can rate up to 28 SEER.
Trane S9X2 Gas Furnace, a finalist in Best Home Technology Products at the 2021 International Builders Show, is a dealer-designed furnace that made technicians’ and end-users’ experience easier and more efficient. Blower housing rails on S9X2 make the blower housing and motor easier to slide in and out of the furnace cabinet for servicing. All of the S9X2’s nine speed taps are electronically selectable with their menu-driven Integrated Furnace Control, allowing technicians to change the airflow setting with option buttons and without having to shut down the unit or a lengthy wiring process. The new Trane furnace also resolves one of the most frustrating features of older furnaces that required technicians to disconnect gas lines, remove the entire set of burners, and replace them after cleaning. The S9X2 burners can be snapped in and out of place one at a time with no disconnections required.
Challenging the status quo
The move to reduce our dependence on fossil-fuel for home heating and to address the desire for single-source heating and cooling has led to innovation and the increased viability of mini-split systems even in our hot and humid climate zones. With that, Heating Seasonal Performance Factor (HSPF) ratings will become a more recognized way to compare efficiency ratings. HSPF indicates the total space heating required during the space heating season, expressed in BTU’s, divided by the total electrical energy consumed by the heat pump system during the same season, expressed in watt-hours. To earn an ENERGY STAR label, a mini-split heat pump must achieve at least 8.5 HSPF. SEER ratings are still used to rate a heat pump’s cooling efficiency.
Mini-split systems implement an outdoor compressor/condenser and indoor air-handling unit. Like a furnace, an air handler is housed in a large metal cabinet where air is conditioned and circulated. The air handling unit itself doesn’t heat or cool the air at all. Instead, it blows indoor air across an internal heat exchanger or coil to add or remove heat from the air without using heating components like the burners and heat exchanger.
Linking the outdoor and indoor units requires only about a three-inch hole though a wall for the conduit housing the power and communication cables, copper tubing and a condensation drain line. Mini-splits have long-been a go-to solution for room additions when extending or installing distribution ductwork isn’t feasible. We’ve also seen them used in super energy efficient homes that require only a small space conditioning system. But the newest air handlers have expanded efficiency and comfort to the point where air handlers are a more mainstream alternative to gas furnaces any climate zone.
Earning a 2021 Green Builder Innovation of the Year Award, the LG Multi-position Vertical Air Handling Unit (VAHU) with LGRED° (Reliable to Extreme Degrees) heating technology features an R1 compressor that can reach speeds up to 135Hz with vapor bypass and vapor injection technologies; this optimizes the VAHU for higher SEER and HSPF ratings across an extremely wide operation range. The LG VAHU is capable of delivering continuous cooling operation to 118°F, 100% heating capacity down to 5°F and continuous heating operation down to -13˚F outdoor ambient temperatures.
Pairing your AC to the furnace
If you’re upgrading or replacing an AC unit in an existing home, you just have to be certain the indoor coil must fit the space above your furnace and that the furnace has enough blower power for the AC. If the AC is a staged or variable speed/modulating AC, however, it may be critical to match the AC to the furnace as well as the thermostat designed for the system to take advantage of communicating control features.
If you’re building new, there are many benefits to using a like-brand furnace and AC. The most advanced products HVAC products feature digital control panels and compatibility for remote access allowing owners to control temperature settings, view operational data, and receive notifications, troubleshooting tips, and historical performance data.
Whole-house systems offered by the major HVAC manufacturers and all put a heightened emphasis on indoor air quality (IAQ), particularly as we begin to climb out of a global pandemic.
Trane’s IAQ program, Tranquility by Trane, equips builders with innovative and efficient strategies to transform traditional heating, ventilation, and air conditioning (HVAC) processes through the application of building science. This approach ensures optimized performance, energy efficiency, and improved occupant health and comfort through superior temperature and humidity control. The Tranquility by Train program and Panasonic’s Intelli-Balance 100 energy recovery ventilator (ERV) were also among the winners for Green Builder’s 2021 Innovation of the Year Awards.
Panasonic’s Intelli-Balance 100 balances pressure in homes, with two electronically commutated motors (ECMs) providing customizable air flow to eliminate positive or negative pressure. The unit comes with a MERV 8 air filter that prevents outdoor particulates, such as pollens and other biologic allergens, from entering the home.
The bottom line: The higher the AFUE, HSPF and SEER rating your equipment is, the higher the cost is likely to be. But the more efficient it is, the more money you can potentially save, meaning a swift payback—but not always. Remember that there are other external factors that can make even your highest level of equipment work harder and use more energy. To avoid oversizing your HVAC, you must consider the home’s size, layout and climate zone. Bigger than needed is not better; in fact, it’s worse. Furthermore, for equipment to operate at its full potential, the system must be installed the right way, your ductwork and building envelope must be adequate and devoid of air leaks, and the equipment must be properly maintained.