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ABC’s of HVAC

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

The world of HVAC is full of technical terms and jargon. We put together this helpful glossary to guide you through all of the verbiage that our Honest Air team uses each and every day. We proudly serve the Frederick and Mt. Airy areas, so if you want to quiz our techs on their HVAC knowledge, just give us a call and let us know!

A-Z HVAC Glossary

A – AFUE (Annual Fuel Utilization Efficiency)

  • Definition: A measurement of how efficiently a furnace converts fuel into heat over a season.
  • What it means: Like a parent trying to get their kids to do chores—only about 50% of the energy goes toward actually getting something done, and the rest is just chaos and distractions

A – Air Handler

  • Definition: The indoor component of an HVAC system that circulates conditioned air.
  • What it means: That big metal box in your basement that makes weird noises when it’s working too hard.

B – Barometric Bypass

  • Definition: A damper that automatically regulates air pressure in an HVAC system by redirecting excess air.
  • What it means: Like a husband tuning out his wife’s “helpful suggestions”—it quietly redirects the extra pressure without starting an argument.

B – BTU (British Thermal Unit)

  • Definition: A unit of measurement that defines how much heat energy is needed to raise the temperature of one pound of water by one degree Fahrenheit.
  • What it means: The number that determines whether you’ll be sweating or freezing in your own home.

C – Capacitor

  • Definition: An electrical component that stores and releases energy in a circuit.
  • What it means: A tiny can of electrical enthusiasm, patiently waiting to dump its energy like a toddler on a sugar rush.

C – Compressor

  • Definition: The heart of an air conditioning system that pumps refrigerant and enables heat exchange.
  • What it means: The part that, when it breaks, will make your wallet cry.

D – Ductwork

  • Definition: A network of tubes that distributes air throughout a building.
  • What it means: A hidden labyrinth where dust, lost socks, and the occasional small tool disappear forever. Did you know that we also provide Duct Cleaning services?

D – Duct Cleaning

  • Definition: The process of removing dust, debris, and contaminants from HVAC ductwork.
  • What it means: Giving your home’s lungs a much-needed deep clean so you’re not unknowingly sharing air with an ancient civilization of dust bunnies and whatever that smell was.

E – EEV (Electronic Expansion Valve)

  • Definition: A device that controls the flow of refrigerant in an HVAC system.
  • What it means: Like a parent setting strict limits on screen time—constantly adjusting to keep things balanced, and somehow it actually works, even if it feels like it’s hanging by a thread half the time.

E – Evaporator Coil

  • Definition: The coil that absorbs heat from indoor air in an air conditioning system.
  • What it means: The thing that turns warm air into cool air, as if by magic (or science).

F – Filter

  • Definition: A component that removes dust and debris from the air before it circulates.
  • What it means: That thing you always forget to change until your AC stops working.

F – Freon

  • Definition: A refrigerant once widely used in air conditioning and refrigeration systems, now phased out and regulated due to environmental concerns.
  • What it means: Like the old family car that was great for years, but now sits in the driveway, banned from the road and replaced by something more eco-friendly, yet still fondly remembered for its coolness.

G – Gas Furnace

  • Definition: A heating system that uses natural gas or propane to warm air before distributing it.
  • What it means: The reason your heating bill skyrockets in the winter.

G – GWP (Global Warming Potential)

  • Definition: A measure of how much a greenhouse gas contributes to global warming compared to carbon dioxide over a specific time period.
  • What it means: Yet another genius acronym the government came up with to regulate us, jack up prices on everything, and somehow make sure your bank account feels like it’s on a permanent diet.

H – Heat Pump

  • Definition: A system that moves heat rather than generating it, used for both heating and cooling.
  • What it means: The all-season workhorse that quietly switches between heating and cooling, doing its best to keep you comfortable—no matter what the weather’s doing outside.

H – Humidity

  • Definition: The amount of moisture present in the air.
  • What it means: The real boss of your comfort level. Too high, and you’re basically a human popsicle melting in the sun. Too low, and suddenly everything’s dry—your skin, your lips, your sense of well-being. The perfect balance? That’s the dream.

I – Indoor Air Quality (IAQ)

  • Definition: A measurement of the cleanliness and health of the air inside a building.
  • What it means: What you suddenly care about after sneezing 14 times in a row.

I – Inverter Compressor

  • Definition: A type of compressor that adjusts its speed to match cooling or heating demand, improving efficiency and comfort.
  • What it means: Like a bartender who actually listens—only giving you as much as you need instead of dumping everything at once and making a mess of the situation.

I – iWave-R

  • Definition: An air purification device that uses ionization to reduce allergens, bacteria, and other airborne particles.
  • What it means: Like having a tiny, invisible bouncer for your air—kicking out unwanted guests like dust, pollen, and whatever mysterious funk your teenager brought home from practice.

J – Jumper

  • Definition: A small wire or connection that allows electricity to bypass part of a circuit, often used in thermostats.
  • What it means: That little piece of wire that somehow keeps the whole system from working—whether you forget to put it in or forget to take it out.

K – Kilowatt Hour (kWh)

  • Definition: A unit of energy representing the amount of electricity used over time.
  • What it means: The number on your electric bill that determines whether you can afford takeout this month.

L – Latent Heat

  • Definition: The heat energy absorbed or released during a phase change (like water turning into steam) without changing temperature.
  • What it means: Like the effort it takes to hold in a sneeze—energy is definitely being used, but somehow, nothing seems to change… until it suddenly does.

L – Load Calculation

  • Definition: A mathematical process used to determine the heating and cooling needs of a building.
  • What it means: The HVAC technician’s secret formula for justifying why you need a bigger unit.

M – Micron

  • Definition: A unit of measurement equal to one-millionth of a meter, often used to gauge vacuum levels in HVAC systems.
  • What it means: So tiny that it makes your bank account after a major HVAC repair look massive by comparison.

M – MERV Rating (Minimum Efficiency Reporting Value)

  • Definition: A rating that indicates the effectiveness of an air filter.
  • What it means: The number that decides whether your allergies will be mild or a full-blown disaster.

M – Mini-Split

  • Definition: A ductless heating and cooling system that allows for independent temperature control in different zones of a building.
  • What it means: Like giving each family member their own thermostat—so your partner can live in an ice cave, the kids can crank the heat to tropical levels, and you can finally exist in peace without starting a household thermostat war.

M – Multipoise

  • Definition: A furnace design that allows installation in multiple orientations (upflow, downflow, or horizontal).
  • What it means: Like that one friend who can sleep anywhere—upright in a chair, sprawled out on the floor, or twisted into some weird position on the couch, and somehow, it just works.

N – Nest Thermostat

  • Definition: A smart thermostat that learns your habits and adjusts temperatures automatically.
  • What it means: The little gremlin that lives on your wall, adjusting the temperature on its own, especially when you’re too warm or too cold—like it knows better than you.

O – Outdoor Unit

  • Definition: The external part of an HVAC system containing the compressor and condenser.
  • What it means: That big noisy box your neighbors complain about when they’re outside.

O – Oversizing

  • Definition: Installing an HVAC system with more capacity than needed for the space, often leading to inefficiency and comfort issues.
  • What it means: Like buying a monster truck for grocery runs—sounds impressive, but you’ll burn through fuel, make everything uncomfortable, and regret your life choices pretty quickly.

P – Plenum

  • Definition: The air distribution box connected to ductwork.
  • What it means: The part nobody knows exists until an HVAC tech starts talking about it.

P – Puron

  • Definition: A brand name for R-410A, once considered an eco-friendly refrigerant but now being phased out for better alternatives.
  • What it means: Like that trendy gadget everyone swore was the future—until we realized it wasn’t all that great and needed an upgrade.

Q – Quiet Mode

  • Definition: A feature on modern HVAC units that reduces operational noise.
  • What it means: The setting you desperately need after realizing how loud your system really is.

R – Refrigerant

  • Definition: The chemical that absorbs and releases heat in an HVAC system.
  • What it means: The magic juice that makes cold air possible (and costs a fortune to refill).

R – Reversing Valve

  • Definition: A valve in HVAC systems that changes the direction of refrigerant flow, allowing the system to switch between heating and cooling modes.
  • What it means: Like when your partner asks, “Do you want to go out for dinner or stay in?” and you instantly flip between options—except this one does it without the guilt trip or 20-minute debate.

S – SEER Rating (Seasonal Energy Efficiency Ratio)

  • Definition: A measure of an air conditioner’s efficiency over an entire cooling season.
  • What it means: The number that tells you whether your AC will bankrupt you or not.

S – Stratification

  • Definition: The layering of air in a space, with warmer air rising and cooler air sinking to the bottom.
  • What it means: Like when you’re in a relationship, and the “hot air” is all the promises and sweet talk that rises to the top, while the cold, hard reality sits at the bottom, waiting to freeze your enthusiasm.

S – Subcooling

  • Definition: The process of cooling refrigerant below its condensation temperature to increase efficiency and prevent overheating in HVAC systems.
  • What it means: Like when you put your drink in the freezer to make it extra cold, but you forget about it, and now it’s way colder than you intended—just a little too much of a good thing, but somehow it works.

S – Superheat

  • Definition: The process of heating refrigerant beyond its boiling point to ensure it’s fully vaporized before entering the compressor.
  • What it means: Like when you leave your coffee in the microwave for way too long—now it’s not just hot, it’s scalding, but at least it’s guaranteed to be fully brewed (and you’re awake for the rest of the day).

T – Thermal Envelope

  • Definition: The barrier that separates the interior of a building from the outside, controlling heat flow and keeping your home energy-efficient.
  • What it means: Like that one friend who swears they can keep a secret—but five minutes later, everything’s leaked, and now you’re left out in the cold, paying for it.

T – TXV (Thermal Expansion Valve)

  • Definition: A valve in refrigeration systems that regulates the flow of refrigerant based on the temperature and pressure of the system.
  • What it means: The little valve that controls your system’s refrigerant like a traffic cop, making sure everything flows smoothly and not too fast or slow (even when you’re not looking).

U – UV Light Air Purifier

  • Definition: A system that uses ultraviolet light to kill bacteria and mold in the air.
  • What it means: The closest thing to Star Wars technology in your HVAC system.

V – Vacuum Test

  • Definition: A process used to remove moisture and air from an HVAC system to ensure it runs efficiently.
  • What it means: Like a trust exercise for your HVAC system—if it holds up under pressure, everything’s good. If not, well… you’ve got leaks, and things are about to get expensive.

V – Ventilation

  • Definition: The process of exchanging indoor and outdoor air for better air quality.
  • What it means: The reason your kitchen smells like last night’s burnt dinner for days.

W – Water Safety

  • Definition: A safety mechanism in HVAC systems that prevents water damage, often in the form of a float switch.
  • What it means: That little switch that stops your HVAC from turning your basement into an indoor water park.

W – Wet Bulb

  • Definition: A temperature reading that accounts for humidity, representing how cool the air feels due to evaporation.
  • What it means: Like sweating on a hot day—if the air’s too humid, your sweat just sits there like a bad date that won’t take the hint. If it’s dry enough, you actually get some relief.

X – eXternal Static Pressure

  • Definition: The pressure in a system caused by external factors, like the air resistance from ductwork, which can affect airflow efficiency.
  • What it means: The mysterious force outside of your HVAC system that’s doing its best to slow everything down—like an invisible villain trying to keep your air from flowing freely.

Y – Y1 and Y2 Terminals

  • Definition: The terminals on a thermostat used to control cooling stages (Y1 for first-stage cooling, Y2 for second-stage cooling).
  • What it means: The places where your thermostat gets fancy and decides whether it’s time for a little chill or a full-blown Arctic blast.

Z – Zoning System

  • Definition: A method that divides a home into separate temperature-controlled areas.
  • What it means: The technology that lets you have an icebox in one room and a sauna in another.

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