HVAC Dictionary
Plain-English explanations of the terms you'll hear during a mini split installation or service call. No jargon, no fluff — just the information you need.
We built this page out of a pattern we kept running into on service calls around Clark and Floyd County: a homeowner standing there holding a quote covered in words nobody bothered to explain. SEER. HSPF. Line set. Load calculation. Condensate drain. A few of them sound like upsells and are not. One or two are the difference between a system sized for your house and a system sized for somebody's convenience.
Every card below opens a full definition — one plain paragraph, no jargon left standing. Start wherever your question is. Reading an installation quote? Load calculation, multi-zone system, and line hide are the three worth knowing first. Something acting up instead? Short cycling, refrigerant, and error code will orient you fast.
These definitions are the companion to our HVAC guides, which walk through the actual failures — an AC that runs but will not cool, a furnace that will not light — using this same vocabulary. Nothing on either page is a sales pitch.
When you would rather have a person than a page, that is us. Henry Brothers diagnoses before quoting and hands you the number in writing, with no trip charge in Clark or Floyd County. A Clean and Check℠ tune-up is $99, and the Two Seasons Membership books both seasonal visits for the year with 10% off every repair.
Installation
Ductless HVAC
Ductless HVAC is exactly what it sounds like — a heating and cooling system that doesn't need ductwork. Instead of…
Mini Split
A mini split is a compact heating and cooling system made up of two main parts: an outdoor condenser unit and one or…
Mini Split Installation
Installing a mini split is usually a one-day job. It involves mounting the indoor air handler on the wall, placing the…
Load Calculation
A load calculation is the process of figuring out how much heating and cooling capacity a space actually needs. It…
Single-Zone System
A single-zone mini split is the simplest setup: one outdoor unit connected to one indoor air handler. It's the right…
Multi-Zone System
A multi-zone mini split runs multiple indoor air handlers off a single outdoor unit. Each indoor unit controls a…
Line Hide
Line hide (sometimes called line cover or lineset cover) is a plastic raceway system that covers the refrigerant lines…
Daikin
Daikin is our preferred mini split brand. They're a Japanese manufacturer with a strong engineering reputation — their…
HVAC
HVAC stands for Heating, Ventilation, and Air Conditioning. It's the broad term for all the equipment that controls the…
Maintenance
Mini Split Maintenance
Keeping a mini split running well doesn't take much, but it does take consistency. The basics include cleaning or…
Condensate Drain
When your mini split cools the air, it pulls moisture out of it — that moisture has to go somewhere. The condensate…
Air Filter
The air filter inside your indoor air handler catches dust, pet hair, and debris before they reach the coil. Most mini…
Clean and Check℠
Clean and Check℠ is our annual mini split tune-up service. It covers the full system: cleaning the indoor air handler…
Parts & Components
Heat Pump
A heat pump moves heat from one place to another instead of generating it from scratch. In the summer, it pulls heat…
Indoor Air Handler
The indoor air handler is the unit mounted on your wall inside the room. It's the part of the mini split you actually…
Outdoor Condenser Unit
The outdoor condenser unit is the box that sits outside your home — it's the other half of your mini split system. It…
Refrigerant Line Set
The refrigerant line set is the pair of copper tubes that connect your indoor air handler to the outdoor condenser…
Refrigerant
Refrigerant is the fluid that circulates through your mini split and actually does the work of moving heat. It absorbs…
Evaporator Coil
The evaporator coil sits inside your indoor air handler and is where refrigerant absorbs heat from the room air. As…
Condenser Coil
The condenser coil is inside your outdoor unit and is where heat gets released to the outside air. In cooling mode, the…
Wall Mount (High-Wall)
The most common type of indoor air handler for mini splits is the high-wall mount — a slim unit installed near the top…
Efficiency
BTU (British Thermal Unit)
A BTU is just a way to measure heating and cooling power. The higher the BTU number, the more air a system can heat or…
Inverter Compressor
An inverter compressor adjusts its speed to match what your room actually needs, instead of just slamming on at full…
SEER Rating
SEER stands for Seasonal Energy Efficiency Ratio, and it tells you how efficiently a cooling system uses electricity…
Zone Cooling
Zone cooling means controlling the temperature in each room independently instead of heating or cooling your entire…
HSPF Rating
HSPF stands for Heating Seasonal Performance Factor. It measures how efficiently a heat pump heats your home over a…
Dehumidification
Dehumidification is the process of removing excess moisture from the air. This matters a lot in Southern Indiana…
Repair
Short Cycling
Short cycling is when your system turns on, runs for a minute or two, shuts off, then starts up again almost…
Reversing Valve
The reversing valve is what allows a heat pump to switch between heating and cooling mode. It redirects the flow of…
Error Code
Mini splits communicate problems through error codes — a sequence of numbers or letters that shows up on the remote…