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How an AC works

HVAC Technician Fixing HVAC attic unit

Just as important as knowing when something is broken is understanding when it's working properly. Then you're more easily and quickly able to identify when something actually goes wrong.

When an HVAC system is functioning properly, it removes warm air from your living or work space and replaces it with cool air. It manages to do this by maintaining a constant cycle of condensation and evaporation. This is how it's done:

The condenser

The condenser is the outdoor unit where the liquid refrigerant starts out. The refrigerant (Freon) comes from inside as a warm gas and it's run through a coil where the latent heat is diffused into surrounding air using attached fins and a large fan. The cool gas continues down the line into the compressor. The compressor, as it name suggests, has the hard job of forcing the gas back into liquid form. This makes the Freon very cold but the process itself releases a lot of heat which is also blown out of the unit by the fan. The compressor pump then sends the cold liquid back into the house.


The Freon arrives, through the line, at the evaporator. Inside this unit, seated on top of the furnace, the refrigerant is once again forced through a coil, this time instead to absorb the latent heat from the air around it. The Freon takes in the heat and evaporates, then gets pumped back outside to start it's cycle again. This process creates a cooling effect making the air passing through he evaporator cold.

Fans, vents and thermostat

Air that was just cooled by the refrigerant in the evaporation unit is blown by the furnace fan up (or down if you have a system in the attic) into the ducts. The duct system, if well insulated, will deliver the air to your vents just as cool as when it left the evaporator. In the same way the cool air is blown out, separate vents pull in warmed air back into the system to be cooled again. When the enough cool air has been delivered into your home to cause the temperature to drop to the desired level the thermostat acts like a switch to shut the system off until the house warms up again.


A big part of keeping your air conditioner functioning properly and increasing it's service life is to make sure it's been installed properly and it's maintenance schedule is kept. Call John C. Flood, the Washington D.C., Alexandria, VA, and Rockville, MD AC installation and maintenance professionals. We perform quality installations and offer great energy star certified products that will keep you cool without costing you too much on your energy bill.

John C. Flood will also perform annual inspections and off-season maintenance. It's important to have your system inspected before it sees heavy use in the summer. Problems that may not be easily identified otherwise can be detected and fixed before they escalate, costing you hundreds in repairs.

Our local technicians are always available to respond to your repair requests and will have your AC back up and running in no time. Give John C Flood a call today.