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HVAC Lingo and Glossary of Terms for Beginners


Air Handler:

Explanation: The indoor component of your HVAC system, responsible for circulating conditioned air. It works alongside the outdoor unit, ensuring even temperature distribution.

Practical Insight: If you have rooms that feel colder or hotter than others, it might be due to uneven air distribution. The capacity and efficiency of the air handler play a crucial role in ensuring consistent comfort.

Air Source:

Explanation: This type of heat pump extracts or releases heat from the surrounding air. It's the most common type of heat pump.

Practical Insight: If you live in a region with milder winters, an air source heat pump can be an energy-efficient method for heating your home.

Air to Air:

Explanation: This system transfers heat between the outside and inside air. In winters, it captures warmth from the external air, and during summers, it extracts indoor heat, releasing it outdoors.

Practical Insight: These systems are versatile, offering both heating and cooling solutions, ideal for climates with distinct summer and winter seasons.

Air to Water:

Explanation: This captures heat from the outside air and transfers it to a water-based system. This water can then be used in radiators or underfloor heating systems. Practical Insight: If you're looking to integrate a heating solution with existing water-based radiators or underfloor systems, this is an ideal choice.


British Thermal Unit (BTU):

Explanation: Represents the energy required to raise the temperature of one pound of water by one degree Fahrenheit.

Practical Insight: A higher BTU indicates greater heating capacity.

A rule of thumb: For every square foot of space, you'll need roughly 20 BTUs. So, a 2,000 square foot home would require a 40,000 BTU heat pump for efficient heating. Adjust this based on insulation, windows, and other factors.


Cubic Feet Per Minute (CFM):

Explanation: Measures airflow velocity, indicating how much air passes a stationary point in a minute.

Practical Insight: When choosing an HVAC system, ensure its CFM matches your space's requirements. Larger rooms or open-plan areas might need systems with higher CFM values for effective temperature regulation.

Carbon Footprint:

Explanation: Represents the total emissions caused by an entity. Efficient HVAC systems have a reduced carbon footprint.

Practical Insight: Choosing energy-efficient heat pumps not only reduces energy bills but also minimizes your environmental impact. Check the system's SEER and HSPF ratings for efficiency indicators.

Closed Loop:

Explanation: A continuous loop of piping, popular in geothermal systems. It acts as a heat exchange medium with the ground.

Practical Insight: Installing a closed-loop system requires significant initial investment due to excavation. However, the energy savings over time can offset this cost, making it a viable long-term solution.

Cold-Climate Heat Pump (CCHP):

Explanation: A specialized heat pump designed to work efficiently in frigid temperatures, typically down to around -35°C.

Practical Insight: If you reside in regions with harsh winters, CCHPs are ideal. They're equipped with advanced compressors and refrigerants to pull warmth from extremely cold air, ensuring you stay cozy even in the depths of winter.


Explanation: A crucial component in the outdoor unit of your heat pump, responsible for maintaining refrigerant flow and converting its state to facilitate heat exchange.

Practical Insight: A well-functioning compressor is key to the heat pump's performance. If you hear loud noises or if the system struggles to heat or cool, the compressor might be at fault. Regular maintenance can extend its lifespan.

Condenser Coil:

Explanation: This coil cools down the hot refrigerant gas, converting it into a liquid. It plays a pivotal role in the heat expulsion process when the system is in cooling mode. Practical Insight: Keeping the condenser coil clean and free from debris ensures optimal performance. A dirty coil can reduce efficiency, leading to higher energy bills and reduced system lifespan.

Coefficient of Performance (CoP):

Explanation: Represents the efficiency of a heating unit by comparing its energy output to its energy input.

Practical Insight: A higher CoP means the system is more efficient. For instance, a CoP of 3 means the heat pump produces 3 units of heat for every unit of electricity consumed. Always check CoP values when comparing heat pumps to ensure you're getting an efficient unit.



Explanation: A device that controls airflow in ducted systems, ensuring even temperature distribution.

Practical Insight: If some rooms in your home feel too hot or cold, the damper settings might need adjustment. Periodic checks ensure they function correctly, distributing air evenly.

Direct Expansion Heat Pump (DX):

Explanation: A geothermal system variant where refrigerant circulates directly through ground loops, absorbing or releasing heat.

Practical Insight: DX systems can be more efficient than traditional geothermal setups as they avoid the water-to-refrigerant heat exchange step. They might require a higher upfront cost but can offer better long-term savings.

Drain Pan Heater:

Explanation: A unit designed to prevent ice formation in the drain pan of the outdoor condenser unit in cold climates.

Practical Insight: If you're in a region where temperatures drop below freezing, consider installing a drain pan heater. It prevents ice buildup, which can damage the unit and reduce efficiency.

Ducted Heat Pump:

Explanation: A system that uses ducts to distribute conditioned air throughout a building.

Practical Insight: Ducted systems are ideal for larger homes or spaces where you want consistent temperatures across multiple rooms. However, they require ductwork, which can be an added expense if not already in place.

Ductless Heat Pump:

Explanation: A system without ducts, often referred to as mini-splits. They have individual indoor units connected to an outdoor compressor.

Practical Insight: Perfect for homes without existing ductwork or for adding comfort to specific rooms. They offer flexibility in placement and can be more energy-efficient since there's no heat loss through ducts.


Efficiency Rating:

Explanation: A measure of how effectively a heat pump can convert energy (usually electricity) into heating or cooling.

Practical Insight: A higher efficiency rating means lower operating costs. Always check the HSPF (for heating) and SEER (for cooling) values when purchasing a heat pump. Over time, a more efficient unit can save significant money on energy bills.

Energy Star:

Explanation: An international standard for energy-efficient consumer products. Products that earn the Energy Star rating typically use 20-30% less energy than required by federal standards.

Practical Insight: Opting for Energy Star-rated heat pumps ensures you're getting a unit that's been tested for efficiency and will likely lead to savings on utility bills. It's also a more environmentally-friendly choice.

Evaporator Coil:

Explanation: Located inside the indoor unit, this coil is where the refrigerant absorbs heat from the indoor air during the cooling cycle.

Practical Insight: The evaporator coil plays a crucial role in cooling your home. Regular maintenance, including cleaning, ensures it operates efficiently. A dirty coil can restrict airflow and reduce the system's ability to cool.

Electronic Expansion Valve (EEV):

Explanation: A modern refrigerant flow control valve that adjusts its opening based on real-time cooling or heating demand.

Practical Insight: EEVs provide more precise control than traditional expansion valves, enhancing efficiency and comfort levels. They can help the system adapt to varying conditions, improving longevity and performance.

Enhanced Vapor Injection (EVI):

Explanation: A technology designed to boost the performance of heat pumps in extremely cold conditions by increasing refrigerant flow.

Practical Insight: If you live in a region with particularly harsh winters, look for heat pumps with EVI technology. They can maintain their heating capacity even when the mercury plummets.



Explanation: Heat pumps that harness the earth's steady underground temperature to provide heating and cooling.

Practical Insight: Although geothermal systems have higher upfront costs, they offer significant savings in the long run due to their efficiency. They are sustainable, environmentally friendly, and can lead to up to 60% savings on heating bills.


Heat Output:

Explanation: The amount of heat a heat pump can produce, typically measured in BTUs. Practical Insight: Ensure the heat pump you select has the right heat output for your space. An undersized unit will struggle to maintain comfort, while an oversized one can lead to short cycling and reduced lifespan.

Heat Pump:

Explanation: A device that transfers heat from a cooler area to a warmer area, providing both heating and cooling capabilities.

Practical Insight: Heat pumps are versatile and can be more efficient than traditional heating systems. They work best in moderate climates but, with advancements like Cold-Climate Heat Pumps, can be effective in colder regions too.

Heating Seasonal Performance Factor (HSPF):

Explanation: A metric used to measure the efficiency of heat pumps in heating mode. Practical Insight: The higher the HSPF, the more efficient the heat pump. For climates with cold winters, selecting a heat pump with a high HSPF can lead to substantial energy savings.

Heating, Ventilation and Air Conditioning (HVAC):

Explanation: A collective term for systems that help maintain indoor environmental comfort.

Practical Insight: Proper HVAC system design and maintenance are crucial for indoor comfort, air quality, and energy efficiency. Regular check-ups ensure the system runs efficiently and prolongs its life.


Explanation: Heat pump systems that combine features of both air-source and geothermal systems.

Practical Insight: Hybrid systems can switch between the sources based on which is most efficient at the time, potentially offering savings on operational costs.


Indoor Airflow:

Explanation: Refers to the movement of air within a confined space, typically measured in cubic feet per minute (CFM).

Practical Insight: Proper indoor airflow is essential for comfort and air quality. Ensuring that HVAC systems are correctly sized and well-maintained helps in achieving and maintaining the desired airflow, enhancing the efficiency of heating or cooling.


Explanation: A device that can vary the speed of the compressor motor of a heat pump to continuously regulate the temperature.

Practical Insight: Heat pumps with inverters are generally more efficient than traditional models because they adjust their output based on demand. This not only conserves energy but also provides more consistent indoor temperatures.


Kilowatt (kW):

Explanation: A unit of power equal to 1,000 watts.

Practical Insight: This unit is often used to express the capacity of larger heating and cooling systems. Knowing the kW rating of a system can help you determine if it's appropriately sized for your needs.

Kilowatt Hour (kWh):

Explanation: A measure of electrical energy equivalent to a power consumption of one kilowatt for one hour.

Practical Insight: Your electricity bill is typically calculated based on how many kWh you've used. Energy-efficient heat pumps can reduce the number of kWh you consume, leading to lower utility bills.



Explanation: The set of tubes through which refrigerant flows between the indoor and outdoor units of a heat pump.

Practical Insight: Proper installation and insulation of the line-set are crucial. Any leaks or inefficiencies can hamper the performance of the entire system.

Load Calculation:

Explanation: A comprehensive assessment to determine the right size of a heat pump for a particular space, considering factors like the size of the area, insulation levels, window types, and more.

Practical Insight: This is a crucial step before installing a heat pump. An appropriately sized heat pump will operate more efficiently and effectively, ensuring comfort and longevity.

Low Ambient:

Explanation: Refers to heat pumps designed to operate efficiently in colder climates. Practical Insight: If you live in an area with harsh winters, it's essential to choose a heat pump labeled as "low ambient" to ensure effective heating even during the coldest days.



Explanation: A type of ductless heat pump system where an outdoor unit is connected to one or several indoor units.

Practical Insight: Mini-splits are versatile and can be a perfect solution for homes without ductwork. Each indoor unit can be controlled independently, allowing for zoned heating and cooling.


Open Loop:

Explanation: In the context of geothermal heat pumps, this refers to systems that draw groundwater from a well or other source, use it to extract or dissipate heat, and then discharge the water.

Practical Insight: While open-loop systems can be efficient, they require a good source of clean water and might be subject to local groundwater discharge regulations.

Outdoor Unit:

Explanation: The component of a heat pump system located outside the building, housing the compressor and condenser coil.

Practical Insight: Regular maintenance, such as cleaning and ensuring proper airflow around the outdoor unit, can enhance its efficiency and prolong its lifespan.



Explanation: A substance used in the refrigeration cycle that changes from gas to liquid and back again, absorbing and releasing heat in the process.

Practical Insight: The type and amount of refrigerant used are crucial for the efficient operation of a heat pump. It's vital to ensure that there are no leaks and that the system is charged correctly.

Refrigeration Cycle:

Explanation: The fundamental process by which heat pumps and air conditioners transfer heat. It involves the continuous evaporation and condensation of the refrigerant.

Practical Insight: Understanding the refrigeration cycle can help homeowners appreciate how their system works, leading to better maintenance practices and more informed decisions when seeking repairs or replacements.


Seasonal Energy Efficiency Ratio (SEER):

Explanation: A measure of the cooling efficiency of heat pumps and air conditioners over an entire cooling season.

Practical Insight: Higher SEER ratings indicate more efficient units. When shopping for a new heat pump, comparing SEER ratings can guide you toward a more energy-efficient choice.


Explanation: A heat pump system designed to serve one specific area or "zone" in a building.

Practical Insight: Single-zone systems are ideal for individual rooms or specific areas of a home that might need additional heating or cooling, such as a sunroom or a newly added section.



Explanation: A device that senses the ambient temperature and adjusts a heating or cooling system to maintain a desired set point.

Practical Insight: Upgrading to a programmable or smart thermostat can enhance the efficiency of your heat pump, allowing for energy savings and improved comfort.

Thermostatic Expansion Valve (TEV or TXV):

Explanation: A valve that regulates the flow of refrigerant into the evaporator coil based on the cooling demand.

Practical Insight: The TXV plays a crucial role in optimizing the performance of a heat pump. It ensures that the right amount of refrigerant enters the evaporator coil, enhancing efficiency and performance.


Variable Speed Drive (VSD):

Explanation: A system that allows the compressor and fan motors of a heat pump to operate at variable speeds, rather than just "on" or "off."

Practical Insight: VSDs offer significant energy savings by adjusting the system's operation based on real-time demand, leading to smoother operation and prolonged equipment life.


Water Source:

Explanation: Refers to geothermal heat pumps that derive their heat from a water source, be it groundwater, a pond, lake, or river.

Practical Insight: Water source heat pumps can be incredibly efficient, especially if there's a consistent water source nearby. However, water quality and availability play crucial roles in the performance and sustainability of these systems.

Additional Terms

Zoning System:

Explanation: A heating or cooling system that uses multiple thermostats and modulating dampers in the ductwork to regulate airflow, allowing different areas or "zones" of a building to be conditioned independently.

Practical Insight: Zoning systems can enhance comfort and energy efficiency, especially in larger homes or buildings where different areas might have varying heating or cooling needs.

Defrost Cycle:

Explanation: A process in which the heat pump temporarily reverses the refrigeration cycle in heating mode to melt frost or ice that accumulates on the outdoor coil.

Practical Insight: The defrost cycle is essential for maintaining the efficiency and performance of a heat pump in colder weather. A malfunctioning defrost cycle can lead to reduced heat output and potential damage to the system.

Energy Recovery Ventilator (ERV):

Explanation: A device that exchanges stale indoor air with fresh outdoor air, recovering heat and moisture from the exchanged air in the process.

Practical Insight: ERVs can improve indoor air quality while maintaining energy efficiency, especially in tightly sealed homes where indoor air can become stagnant.

Ground Loop:

Explanation: Refers to the piping system buried in the ground that circulates fluid in a geothermal heat pump system. The fluid absorbs heat from or releases heat to the earth.

Practical Insight: The efficiency of a geothermal heat pump heavily relies on the ground loop. Proper installation depth and length, based on local soil conditions and climate, can greatly impact system performance.

Reversing Valve:

Explanation: A component in heat pumps that changes the direction of refrigerant flow, allowing the system to switch between heating and cooling modes.

Practical Insight: A malfunctioning reversing valve can prevent a heat pump from switching modes. It's a crucial component that ensures the heat pump's versatility in providing both heating and cooling.




The information provided in this article is subject to change without notice. Ace Heat Pumps is not responsible for the accuracy or completeness of this information and disclaims any liability arising from its use. Always consult directly with official sources for the most up-to-date information on rebates and incentives.

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