The Ultimate Ductless HVAC Glossary

Welcome to N.E.T.R., Inc’s Ultimate Ductless HVAC Glossary. Browse the most common terms and their definitions, plus learn how to get in touch with our team of certified technicians for help with your heating and cooling.

Top Terms to Know About Ductless HVAC

Air Handler

An air handler is the interior component of a ductless HVAC system that is responsible for circulating warm or cool air throughout your space. Depending on the brand, these units will typically feature advanced filtration and customized airflow options.

Air Quality

Air quality describes how clean the air is within a specific environment. The quality of your indoor air can be significantly lowered by the presence of things like dust, pollen, pet dander, VOCs, and high humidity. Having a reliable HVAC system can help filter these particulates out of your air.

Allergen

An allergen is a substance that triggers an allergic reaction. The most common allergens found indoors are pollen, pet hair, dust, mold, mildew, smoke, bacteria, and cooking oil. The more allergens that are present in your air, the lower your air quality is.

Blower

A blower is a motor that powers a fan inside your mini split’s indoor unit. This distributes heated or cooled air evenly throughout your space.

British Thermal Unit (BTU)

A British Thermal Unit, or BTU, is a measurement of how much heat energy is needed to increase the temperature of one pound of water by one degree Fahrenheit. Ductless HVAC systems tend to have high BTU ratings, which means they have greater heating capacities and can keep your space warmer compared to space heaters, furnaces, and wood or pellet stoves.

Carbon Footprint

A carbon footprint is the amount of greenhouse gas that a person, company, event, or other entity emits into the environment and is measured in tons.

CFM

Cubic Feet Per Minute (CFM) is a measurement of how much air passes by a specific point in one minute’s time. Systems with high CFM ratings can cool or heat a space much faster than systems with low ratings. If a system’s CFM rating is very low, this could indicate a problem with the unit. 

Compressor

A compressor is a component located in the outdoor unit of a ductless system that compresses gaseous refrigerant and turns it into hot vapor.

Condenser

A condenser consists of a set of coils that receive the superheated vapor from the compressor. As the vapor flows through these coils, it gets cooled by a fan and turns back into liquid refrigerant.

Coefficient of Performance (COP)

The Coefficient of Performance (COP) is a measurement of how efficient mini split heaters are. It’s expressed as a ratio that represents the amount of heat output compared to energy used. The greater a ductless system’s COP, the more efficient the unit is. For example, a traditional furnace or baseboard heating element might have a COP of 1. A mini split, on the other hand, could have a COP of 3.5 or greater. 

Cycling

Cycling occurs when an HVAC system turns on and off. While central systems use cycling to maintain the temperature in a space, ductless systems have variable speed motors that allow the fan to increase or decrease by small increments, which helps to save more energy and puts less wear and tear on the system than cycling.

Decibel (dB)

A decibel (dB) is a measurement of sound intensity or volume. Normal conversations typically clock in at 50 to 60 dB, while a whisper is around 30 dB. A motorcycle going down the highway could be as loud as 90 to 100 dB. To compare, a ductless unit operates at roughly 30 dB, even outdoors – so quite literally whisper quiet.

Ductless

Ductless is a term used to refer to mini split systems that do not require air ducts to transfer heated or cooled air throughout a space. These are also called heat pumps and consist of an outdoor condenser and at least one indoor air handler, which is typically mounted on the wall in your desired space. Ductless HVAC systems do not suffer from the same kind of heat loss that occurs with ductwork and are significantly more energy efficient and cost effective than central heating and cooling.

ENERGY STAR®

ENERGY STAR® is a program created by the Environmental Protection Agency (EPA) to help reduce America’s reliance on fossil fuels and manage overall energy consumption. Heating and cooling equipment with an ENERGY STAR® rating can be up to 7 to 15% more efficient than standard furnaces and air conditioners. Ductless HVAC systems with an ENERGY STAR® label adhere to strict federal guidelines and can provide superior performance for both residential and commercial applications.

Environmental Protection Agency

The United States government oversees federal regulations for refrigerant use, efficiency ratings, and other critical aspects of heating and cooling equipment through the Environmental Protection Agency (EPA). The EPA also regulates pesticide use, pollutant emissions, industrial chemicals, and other ecological hazards.

Evaporator Coil

An evaporator coil is a mechanism within a ductless system’s indoor air handler. It works to facilitate the heat exchange process by either absorbing heat from inside your space or releasing it depending on the season and your unit’s settings.

FAD

FAD is an acronym that stands for Factory Authorized Dealer. This means that the manufacturer has verified the dealer and authorizes them to represent the brand.

Filters

All heating and cooling systems with air intake have filters. These are made from finely woven materials that catch particulate matter while allowing air to pass through. Air filters are rated based on how porous they are and the size of particulates that they can catch. The more porous a filter, the lower its ratings will be and the less protection it provides.

Heat Loss

Heat loss is a term that refers to the amount of heat that seeps through cracks in ductwork, poor insulation, drafty windows, and other small openings. While some heat loss is an indicator of healthy ventilation in a building, too much can increase your energy bills and make your space uncomfortable.

Heat Pump

A heat pump is an appliance that uses heat transfer technology to heat or cool a home. Also called ductless mini splits, these devices work by extracting heat from one place and moving it to another. For example, a ductless system will remove heat from your space in the summer and pump it outside to create a cooling effect. When temperatures drop and the season changes from fall to winter, the pump reverses to extract heat from outdoors so it can be transported inside to keep your space warm. Depending on the type of heat pump you have, it may be as much as 200% to 350% more energy efficient than electric baseboards or a gas furnace.

HSPF

HSPF is an acronym that stands for Heating Seasonal Performance Factor, which is a system used to rate the efficiency of ductless heat pumps in the winter. The higher the HSPF, the less energy it has to use to generate the same amount of heat as a system with a lower rating. HSPF is similar to the Coefficient of Performance, which also measures the amount of heat produced versus energy used. However, HPSF measures annual efficiency performance, while COP is more general and covers the system’s lifespan.

HERS

HERS is an acronym that stands for Home Energy Rating System. This is a set of guidelines that measure how energy efficient a home is and helps determine what upgrades need to be made to improve energy usage. Houses are scored on a scale of 0 to 150, with 0 representing homes that break even by generating as much energy as it uses.

Humidity

Humidity is a measurement of how much moisture or water vapor is in the air and is expressed as a percentage of 100. The more humid a space is, the hotter it will feel. The reverse is also true and the warmer the air is, the more humidity it can hold.

IAQ

(see Air Quality)

Inverter

Ductless HVAC systems use inverter technology to reduce the amount of energy wasted during operation. This works by adjusting the motor speed up or down in small increments to raise or lower temperature in a space instead of cycling on and off like a central system. These units can save up to 30% more energy than traditional HVAC.

Kilowatt Hour (kWh)

A kilowatt hour (kWh) is a measurement of how much electricity is used by an appliance over an hour’s time.

Load Calculation

A load calculation is a detailed assessment of how much energy you need within your home or office. This is often referred to as a “Manual J” calculation and determines the exact number of BTUs your system should have based on variable factors like the size and layout of your space, how high your ceilings are, how much insulation there is, if the room is in direct sunlight at any point during the day, and other specific factors that can change how much heating or cooling you need at any point in time to stay comfortable.

MERV

MERV is an acronym for Minimum Efficiency Reporting Value. This figure is a rating of how efficient an air filter is, or how many tiny holes it has that allow potentially harmful particles to pass through. Filters with higher MERV ratings have smaller holes and prevent more particles from getting into your air. 

Mini-Split

The term mini-split is another name for a ductless HVAC system, which is also sometimes referred to as a heat pump. These appliances are called mini-splits because they’re smaller than traditional HVAC systems and they are “split” between an indoor air handler and an outdoor compressor.

Multi-Zone

A multi-zone ductless system features one or more outdoor units with two or more indoor air handlers. This creates different temperature zones that can be individually controlled to increase comfort or save additional energy. You can connect an outdoor condenser to up to 8 indoor units before you will need to have an additional outdoor unit.

Preventative Maintenance

Preventative maintenance refers to keeping your ductless system in good condition over time, similar to how vehicles are taken to the mechanic for oil changes. Preventative maintenance generally includes inspecting for worn or damaged components, lubricating moving parts, and replacing materials as needed to prevent catastrophic breakdowns.

Programmable Thermostat

A programmable thermostat is a device that can adjust your heat pump’s temperature settings based on a preset schedule. This allows users to program their thermostats to use less energy when they are sleeping or away from home, while optimizing comfort when they are using the space. Not only does this save you money, it also reduces your carbon footprint and puts less wear and tear on your system over time.

Refrigerant

Refrigerant is a chemical compound that serves as the mechanism by which HVAC works. As it travels through your system, refrigerant continually transforms back and forth between gaseous and liquid states to absorb and release heat at the right times.

SEER

SEER is an acronym that stands for Seasonal Energy Efficiency Ratio. This measurement is used for air conditioners and ductless mini splits to assess how much annual cooling output a system provides compared to how much energy it uses during that year. The higher the SEER rating, the more efficient the unit is.

Single Zone

A single-zone ductless system includes one outdoor compressor connected to one indoor air handler via a set of copper tubes called refrigerant lines. Single-zone systems are ideal for bedrooms, living rooms, attics, and other small spaces where you might want individual temperature controls.

Thermostat

A thermostat is a device that monitors the temperature in your home and controls the settings of your ductless HVAC system. If your thermostat senses the temperature is too high or low, it will signal your system to adjust the heating or cooling to match your preferred settings. These are generally located in an interior spot, away from windows, refrigerators, stoves, and water heaters. 

Tonnage 

Tonnage refers to the capacity that a ductless system has to cool a space. A 1-ton mini split can remove 12,000 BTUs of heat from your air each hour for 1 day, while a 2-ton mini split would be able to remove 24,000 BTUs of heat. This is equivalent to the cooling capability that 1-ton of ice would have during the same 24-hour period of time.

Variable Speed Motor

A variable speed motor works alongside the inverter in a ductless system to increase or decrease fan speed based on the temperature requirements of your home or office. Instead of having your system shut off when your space reaches the ideal temperature, a variable speed fan will simply slow down to provide less airflow to the area. When you need more heating or cooling, the fan speed will increase.

VOCs

The acronym VOC stands for Volatile Organic Compound. These are harmful substances that can remain in the air and contain dangerous carbon and other chemicals. Even though VOCs are harmful to pets and humans, they are often found in high quantities in residential homes. VOCs can come from things like incense, candles, new furniture, paint, hairspray, dry-cleaned clothes, and many other common items that most people don’t think twice about.

Zoning

Zoning is a systematic approach to dividing a space into separate areas and equipping each area with its own climate control. One outdoor ductless unit can house up to 8 indoor air handlers that can be adjusted individually based on factors like user preferences and when you’re home or away.

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N.E.T.R., Inc. provides comprehensive ductless HVAC services in Boston and surrounding areas. Contact us today to learn more or schedule service by calling (781) 428-4478 or fill out our quick web form and we’ll get in touch.