Glossary of HVAC Terms
Here are some common terms and their translations used around the HVAC world:
- Compressor: “Vapor compressor” This is designed to increase temperature of refrigerant in order to increase temperature. Outdoor Unit
- Condenser Coil: “Heat rejector” Outdoor unit that exhausts hot air absorbed from the refrigerant.
- Filter Drier: Absorb water vapor in the system so that the water vapor isn’t mixed with the refrigerant. Saves the compressor which is an electrical motor system & wires that is hermetically sealed. Has limited capacity.
- Metering Device: “Pressure Dropper” Lower temperature of refrigerant in order to decrease temperature
- Evaporator: “Heat Absorber” – Indoor coil.
- Indoor Blower Motor: the fan on the HVAC which causes the outgoing air to circulate out of the system and into the rooms of your home. The blower motor is the part of your HVAC system that gets your home to the temperature set on your thermostat.
- Vapor Line: On a split system heat pump, the connecting lines are the vapor line and the liquid line. The vapor line can be cool suction vapor or hot gas depending on the mode of operation (heat/cool).
- Access Port: Usually a small valve opening designed to check pressure. It does not have a service valve so it cannot control the flow of refrigerant.
- Service Valve: A manually operated valve used for checking the pressures, normally found on the compressor.
- Compressor Inlet: This controls the capacity of a rotary screw compressor. By opening and closing the air intake, the capacity of a rotary screw compressor can change.
- Refrigerant: Something that we’re continuously pressurizing & depressurizing in order to manipulated the temperature. Also cools down the compressor motor. Boiling refrigerant effectively removes heat from the air that’s passing over it.
- Ideal Gas Law: Pv = nRT (pressure + volume = mass + temperature). If you change any of these units, you change them all. Mass tends to remain more constant. Increasing pressure of refrigerant = increasing temperature. Decreasing pressure of refrigerant = decreasing temperature
- Temperature: Average molecular velocity. The average speed that the molecules are moving within a substance.
- Scroll Compressors: Round & tall, generally 1 cylinder. Compression of the refrigerant takes place inside the scroll wrap with the help of scrolls. Works in circular motion vs up and down.
- Rotary Compressors: Round with two cylinders. These are hermetically sealed. A rotary compressor compresses refrigerant inside its compression chamber with the help of the rotary motion of the roller and vertical movement of the vane
- Reciprocating/Piston Compressors: Oval (looking down) in ACs. Most common and long standing. Uses pistons driven by crankshaft to compress refrigerant & move it with high pressure.
- Heat Exchangers: Unit that transfers heat between two (or more) fluids. These are energy efficient.
- Shell & Tube: A bunch of tubes that contain cooler liquid are looped in a cylindrical container (pressurized shell) that hot liquid circulates through. It is the most common type of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. Exchanges heat between the fluid in the tubes.
- Plate Heat Exchangers: Company & efficient. Fluid moving between the plates, plates touch and exchange heat off each other. Can increase or decrease depth. Pattern on plates create turbulent flow which increases the heat transfer. Gaskets separate the plates creating a thin channel between them for the fluid to flow. The thermal energy flows through the sheets.
- Air Cooled Condensers: Typical type. Air is drawn over the metal fins/grates.
- Thermostatic Expansion Valve (TXV): A lot better at controlling the super heat across the evaporator coil in order to reduce the humidity & heat load in the building really quickly. Much faster than a piston or fixed orifice metering device would be able to do. Got a bad reputation for leaking, but new ones are stainless steal vs older metal.
- Capillary Tube: Seen in smaller appliances like window units, refrigerators. This has a fixed orifice. The phase change of the refrigerant is smaller due to the smaller amount of refrigerant making it’s way through the orifice. This makes more super heat.
- Piston Device: Found more on 0lder/low efficiency systems. This has a fixed orifice. The phase change of the refrigerant is smaller due to the smaller amount of refrigerant making it’s way through the orifice. This makes more super heat.
- Electronic Expansion Valve (EEV or EXV): Just like the TXV except it using electronics to monitor it.
- Discharge Line: Line between compressor & condenser.
- Liquid Line: Line between condenser and metering device.
- Suction Line: line that goes back from the evaporator to the compressor. The suction line is to return gas to the compressor. It is between the evaporator and compressor on a standard cooling system and between the reversing valve and the compressor on a heat pump.
- Expansion Line: (not always there). Sometimes found on ductless systems, not as common).
- HSPF: Heating Seasonal Performance Factor
- SEER: Seasonal energy efficiency ratio. Higher SEER rating means high efficiency within the system. The more efficient the system, the more money saved. Calculated by dividing the total amount of heat removed from the house BY the total energy consumed by the cooling system.