Friday, July 26, 2013


     Before doing any work yourself or talking to any HVACR technician it is important to get your HVACR technical terminology right so you can at least communicate. The following are some common terms with not-so-technical explanations:

Condenser is the outside unit which consists the condenser fan motor, compressor and some electrical components like contactor, capacitor etc.

Evaporator Coil is the unit that sits on top or on the side of your furnace that connects to the condenser.

Furnace is the heating unit that uses natural or LP gas to heat your home. It consists of a blower motor, gas components (pilot, gas valve, flame sensor etc.) and some electrical components (control board, relay, capacitor etc.). It is located in the garage or attic most of the time.

Packaged Unit is an a/c unit that has all the components within the unit instead of having a split system like a condenser and evaporator separately. Packaged unit will simply blow hot air or cold air into the house.

Gas/Electric is an unit that runs on electricity to provide cooling (compressor) and gas to provide heating (combustion).

Heat Pump is an unit that runs on electricity (compressor) only to provide both heating and cooling.

Liquid line is the copper tubing with the smaller diameter that runs from the condenser to the evaporator coil. It is where the liquid refrigerant travel from the condenser to the evaporator coil.

Suction line is the copper tubing with the larger diameter that runs from the evaporator coil to the condenser. It is where the gas refrigerant returns from the evaporator coil back to the condenser.

Thermostatic Expansion Valve or TXV is a metering device that forces liquid refrigerant into gas refrigerant according to the temperature sensed by its probe. Usually it is located in the evaporator coil.

Basically how a typical residential split system work is like this: When calling for cool, the compressor runs and compresses the low pressure/low temperature gas refrigerant into a high pressure/high temperature gas refrigerant. The condenser coil then cools it so it becomes a high pressure liquid refrigerant and travel thru the liquid line to the evaporator coil. Then the TXV restricts how much refrigerant can go thru and thus high pressure liquid refrigerant will become gas refrigerant and in the process will absorb heat thus cooling the evaporator coil. The furnace blower forces air thru the evaporator coil into you house so you have cool air out from the registers. Low pressure gas refrigerant then goes back to the condenser thru the suction line and starts the process again. When calling for heat, the furnace simply turns on the gas valve and ignites the combustion process while blower force air thru the chamber so you have warm air coming out from the registers. Both condenser and evaporator coil are not in use when system is calling for cool. Well, this should be enough for one day, now that you know the basic names lets talk about common a/c problems next week. Have a great weekend.

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