Understanding your heating and cooling system shouldn’t require a technical degree. At Sigler Heat and Air, we believe that informed homeowners make better decisions about their comfort systems. That’s why we’ve compiled this comprehensive glossary of HVAC terminology to help you navigate conversations about your home’s heating and cooling needs with confidence.
As Tulsa’s most trusted HVAC company since 1947, we’ve seen how technical jargon can create confusion during important service discussions. Our technicians always explain these terms during service visits, but having this reference guide can help you feel more empowered when making decisions about your home comfort systems.
AFUE (Annual Fuel Utilization Efficiency)
A measurement of a gas furnace’s efficiency in converting fuel to energy. A higher AFUE percentage indicates a more efficient furnace. For example, a 96% AFUE furnace converts 96% of its fuel into heat, while only 4% is lost in the combustion process.
Modern high-efficiency furnaces typically have AFUE ratings between 90-98%, while older systems might operate at just 60-70% efficiency. This significant difference explains why upgrading an aging furnace often results in noticeable energy savings.
Air Balancing
The process of adjusting various components of an HVAC system to provide the proper airflow to each room in a building. Proper air balancing eliminates hot and cold spots, improves comfort, and maximizes system efficiency.
Air Handler
The indoor component of your HVAC system that circulates conditioned air throughout your home. It houses the blower fan, evaporator coil, and other essential components. Think of it as the heart of your indoor comfort system, pumping conditioned air through the “veins” of your ductwork.
Blower Motor
The component that powers the fan that moves air through your HVAC system. Blower motors come in single-speed, multi-speed, and variable-speed varieties, with the latter providing the most comfort and efficiency.
Variable-speed blower motors, which we often recommend at Sigler Heat and Air, can improve comfort substantially by providing more consistent temperatures and better humidity control compared to traditional single-speed motors.
BTU (British Thermal Unit)
The standard measurement of heat energy used in the heating and cooling industry. One BTU represents the amount of energy needed to raise one pound of water by one degree Fahrenheit. HVAC systems are typically rated in thousands of BTUs per hour (MBH).
Your home’s size, insulation level, and local climate determine how many BTUs your system needs to maintain proper comfort levels. A system with too few BTUs won’t keep up with demand, while one with too many will cycle on and off frequently, reducing efficiency and comfort.
Capacity
The output capability of a heating or cooling system, typically measured in BTUs (British Thermal Units) per hour. Proper capacity sizing is crucial for both comfort and efficiency – an improperly sized system will either struggle to maintain comfort or waste energy through excessive cycling.
Our experienced technicians perform detailed load calculations to ensure any system we install is precisely matched to your home’s requirements.
Combustion Analysis
A test performed on gas heating equipment to measure efficiency and ensure safe operation. This analysis examines factors like carbon monoxide levels, draft pressure, and combustion efficiency to verify that your furnace is operating safely and at peak performance.
Compressor
The heart of your air conditioning system, responsible for pressurizing and circulating refrigerant through the system. The compressor takes low-pressure refrigerant gas and compresses it into a high-pressure, high-temperature gas that begins the cooling cycle.
There are several types of compressors, including:
- Scroll compressors (most common in modern residential systems)
- Reciprocating compressors (found in older systems)
- Rotary compressors (compact and efficient)
- Variable-speed compressors (offer precise temperature control)
Condenser
The outdoor unit of your air conditioning system containing the compressor, condenser coil, and a fan. It releases the heat collected from inside your home to the outdoor air. Regular cleaning and maintenance of your condenser unit are essential for efficient system operation.
Conditioned Air
Air that has been heated, cooled, humidified, or dehumidified to meet desired indoor comfort levels. This is what your HVAC system delivers to your living spaces through supply vents.
Cycling
The process of an HVAC system turning on and off. Excessive cycling (short-cycling) can indicate an oversized system, while too few cycles might mean the system is undersized or struggling to meet demand.
At Sigler Heat and Air, we often find that proper maintenance and correctly sized equipment can significantly reduce cycling issues, extending system life and improving comfort.
Damper
A plate or valve that regulates airflow within a duct, chimney, or other air-handling equipment. Dampers can be manual or automatic and are used to balance the airflow throughout your home. Properly adjusted dampers ensure even temperatures throughout your home and can help address areas that are consistently too hot or too cold.
Ductwork
The network of tubes that distributes conditioned air from your HVAC system throughout your home. Ductwork can be made from various materials, including sheet metal, fiberglass, or flexible plastic. Properly sized and sealed ductwork is crucial for system efficiency.
Leaky ducts can reduce your system’s efficiency by 20-30%. At Sigler Heat and Air, we often find that repairing ductwork issues can significantly improve comfort and reduce energy bills without requiring system replacement.
Economizer
A mechanical device used in commercial HVAC systems that uses outside air for cooling when temperature and humidity conditions are favorable, reducing the need for mechanical cooling and saving energy.
EER (Energy Efficiency Ratio)
A measure of how efficiently an air conditioner operates when the outdoor temperature is at a specific level (usually 95°F). The higher the EER rating, the more energy-efficient the unit. This rating is particularly important in hot climates like Tulsa’s where air conditioners run for extended periods.
Evaporator Coil
The indoor component where heat from your home’s air is absorbed by refrigerant. It’s typically located inside the air handler or attached to the furnace. The evaporator coil works together with the condenser to transfer heat from inside your home to the outside.
Regular maintenance of your evaporator coil is essential, as dirt and debris can act as unwanted insulation, reducing efficiency and potentially leading to system failures. This is one reason why annual maintenance is so important.
Filter (Air Filter)
A device that removes particles like dust, pollen, and mold spores from the air circulating through your HVAC system. Filters come in various efficiency ratings (MERV ratings) and should be changed regularly to maintain proper airflow and indoor air quality.
How often should you change your filter? It depends on several factors:
- Basic 1-inch filters: Every 30-90 days
- Medium-efficiency pleated filters: Every 3-6 months
- High-efficiency filters: Every 6-12 months
- Homes with pets or allergies: More frequent changes needed
Flash Code
A series of blinking lights on your furnace control board that indicates specific system issues. These codes help technicians quickly diagnose problems. Each manufacturer uses different patterns of flashes to communicate different issues.
Our technicians are trained to interpret flash codes across all major brands, allowing for faster and more accurate diagnosis of your system’s issues.
Heat Exchanger
A component inside a furnace that transfers heat from the combustion process to the air circulating through your home. The heat exchanger keeps combustion gases separate from your breathing air – which is why cracks in this component are a serious safety concern.
Regular maintenance helps identify potential heat exchanger issues before they become safety hazards. At Sigler Heat and Air, our thorough inspections include detailed examination of this critical component.
Heat Pump
A versatile HVAC system that can both heat and cool your home by transferring heat between the indoor and outdoor air. Heat pumps are particularly efficient in moderate climates but can struggle in extreme temperatures without supplemental heating.
Our technical expertise at Sigler Heat and Air has helped many Tulsa homeowners determine if a heat pump is right for their specific needs, as they work well in our climate for much of the year.
HSPF (Heating Seasonal Performance Factor)
A rating that measures the heating efficiency of heat pumps. The higher the HSPF, the more efficient the unit. Current minimum standards require new heat pumps to have at least 8.8 HSPF, but high-efficiency models can reach 13 HSPF or higher.
Humidifier/Dehumidifier
Devices that add or remove moisture from the air in your home. Maintaining proper humidity levels (typically 35-50%) improves comfort, prevents mold growth, and protects wooden furnishings and structural elements from damage.
Oklahoma’s climate often requires both technologies at different times of the year – humidification during dry winter months and dehumidification during humid summers.
HVAC
Stands for Heating, Ventilation, and Air Conditioning. This term encompasses all the systems and technologies used to move air between indoor and outdoor spaces, heat and cool a building, and clean the air.
Indoor Air Quality (IAQ)
A term referring to the air quality within buildings, especially as it relates to the health and comfort of building occupants. IAQ can be affected by microbial contaminants, volatile organic compounds (VOCs), carbon dioxide, and particulates.
Poor indoor air quality can contribute to health issues including:
- Respiratory problems
- Headaches and fatigue
- Allergy symptoms
- Asthma triggers
- Eye, nose, and throat irritation
Load Calculation
A process used to determine the heating and cooling requirements of a building or room. Proper load calculation ensures that the HVAC system is correctly sized for the space. This calculation takes into account factors like square footage, ceiling height, insulation values, window sizes and types, and local climate conditions.
At Sigler Heat and Air, we perform detailed load calculations before recommending any system replacement. Many companies skip this crucial step, leading to oversized systems that cycle too frequently or undersized systems that can’t keep up with demand.
Manual J
An industry-standard calculation method used to determine the proper size of HVAC equipment needed for a specific home. This detailed analysis takes into account factors like square footage, insulation values, window size and placement, and local climate conditions.
Unlike many contractors who rely on rough estimates or simply replace equipment with the same size that was previously installed, Sigler Heat and Air technicians perform proper Manual J calculations to ensure optimal system sizing.
MERV Rating (Minimum Efficiency Reporting Value)
A scale from 1 to 16 that rates the effectiveness of air filters. The higher the MERV rating, the smaller the particles the filter can trap. However, higher MERV filters can restrict airflow if your system isn’t designed for them.
Modulating/Variable-Speed Equipment
HVAC components that can operate at varying levels rather than simply being “on” or “off.” These systems provide more precise temperature control, improved humidity management, and greater energy efficiency.
Variable-speed technology can:
- Reduce temperature swings
- Lower energy consumption
- Provide better humidity control
- Operate more quietly
- Improve overall comfort
Plenum
A box-like chamber at the beginning of the duct system that distributes air from the air handler or furnace to the individual ducts. The plenum functions as the central distribution point for your conditioned air.
Preventative Maintenance
Regular scheduled service designed to keep HVAC equipment running efficiently and identify potential problems before they cause system failure. Proper maintenance typically includes cleaning coils, checking refrigerant levels, inspecting electrical components, and verifying proper operation.
Our Customized Maintenance Program provides tailored preventative care to extend your system’s lifespan, maintain efficiency, and prevent costly emergency repairs.
Psychrometrics
The study of the physical and thermodynamic properties of air-water mixtures. Understanding psychrometrics is essential for properly designing and operating HVAC systems that effectively control temperature and humidity.
Recovery Mode
When a programmable thermostat begins adjusting temperature ahead of schedule to reach the desired temperature at the programmed time. For example, if you set your thermostat to be 72°F at 5:00 PM, recovery mode might begin cooling your home at 4:30 PM to ensure it reaches 72°F by your arrival.
Refrigerant
The chemical compound used in air conditioning systems that absorbs heat from one area and transfers it to another. Common types include R-410A (current standard) and R-22 (phased out due to environmental concerns).
Refrigerant Charge
The amount of refrigerant in an air conditioning or heat pump system. Proper charging is crucial for system efficiency and performance. An undercharged or overcharged system can significantly reduce efficiency and lead to premature component failure.
As technical experts in HVAC systems, our technicians precisely measure and adjust refrigerant charge to manufacturer specifications, ensuring optimal system performance.
Return Air
The air that flows back to your HVAC system for reconditioning. Return vents are typically larger than supply vents and are often located in hallways or central locations in your home.
SEER (Seasonal Energy Efficiency Ratio)
A measure of air conditioning and heat pump cooling efficiency. The higher the SEER rating, the more energy-efficient the unit. Current minimum standards require new central air conditioners to have at least 14 SEER in the southern United States, including Oklahoma.
When considering system replacement, the SEER rating is an important factor in determining long-term operating costs. While higher SEER units cost more upfront, they can provide significant energy savings over time, especially in Tulsa’s hot summers.
Static Pressure
The resistance to airflow in a duct system, measured in inches of water column (inwc). High static pressure can indicate restrictions in the ductwork that reduce system efficiency and capacity, while also increasing energy consumption.
Supply Air
The conditioned air that flows from your HVAC system into your living spaces. Supply vents are typically located in the floor, ceiling, or walls of each room.
Thermal Zone
An area in a building that has consistent heating and cooling requirements throughout. Multiple thermal zones typically require separate temperature controls for optimal comfort.
Thermostat
A device that regulates the operation of your heating and cooling system to maintain desired temperature settings. Modern programmable and smart thermostats can automatically adjust temperature settings based on schedules or other factors, improving both comfort and efficiency.
Smart thermostats can learn your preferences, adjust based on whether you’re home, and even respond to weather forecasts. Many of our customers find that upgrading to a smart thermostat is one of the most cost-effective improvements they can make to their HVAC system.
Tonnage
A term used to describe the cooling capacity of air conditioning systems. One ton equals 12,000 BTUs per hour. Most residential systems range from 1.5 to 5 tons, depending on the size and requirements of the home.
It’s a common misconception that “bigger is better” when it comes to air conditioning tonnage. An oversized system will cool your home quickly but cycle off before properly dehumidifying the air, leading to comfort issues and potential mold problems.
Two-Stage/Multi-Stage Equipment
Heating and cooling systems that can operate at different output levels depending on demand. Unlike single-stage equipment that operates at full capacity whenever it’s running, multi-stage systems can operate at lower capacities during mild weather, providing better efficiency and comfort.
Zoning System
A method of dividing a home into different areas or “zones” with separate temperature control. Zoning allows for customized comfort levels in different parts of the home and can improve energy efficiency by conditioning only the areas that need it.
Zoning systems are particularly beneficial for:
- Homes with multiple levels
- Houses with large open areas and small rooms
- Spaces with large windows or specific solar exposure
- Families with different temperature preferences
Understanding HVAC Terms Leads to Better Decisions
Knowledge is power, especially when it comes to your home’s comfort systems. By familiarizing yourself with these HVAC terms, you’ll be better equipped to discuss your heating and cooling needs with technicians and make informed decisions about repairs, maintenance, and eventually, system replacement.
At Sigler Heat and Air, we believe in empowering our customers through education. As Tulsa’s oldest Carrier dealer and a third-generation family business since 1947, we’ve built our reputation on technical expertise combined with honest, straightforward communication.
Have questions about your HVAC system that weren’t covered in this glossary? Contact our expert technicians today. We pride ourselves on being able to explain complex HVAC concepts in terms anyone can understand—while having the technical mastery to solve problems others can’t.
Remember, we send technicians, not salespeople, to your home. You’ll always get honest assessments focused on what’s best for your system and your comfort needs.
