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Central Air

So How Exactly Does Central Air Conditioning Work?

Central Heat and Air is the most common air conditioning system in Los Angeles. Central Heat and Air are sometimes also called ‘forced air’, or a ‘split system’.  Central Heating and Air uses air as its heat transfer medium.  The system relies on ducts and fans to circulate the conditioned air throughout the house. An advantage central heat and air has over a boiler or a hydronic system is that there is no water, so there is no risk of structural damage due to a water leak. An advantage a Central Air system has over a Heat Pump is that the furnace heats very quickly. To install a central air and heat system will cost $12,000 to $14,000 for a 2,000 sqft house. The cost is split between buying the condenser ($2,000-$3,000) the furnace ($2,000-$3,000) and the ducting ($5,000-$6,000) plus installation. It is a 2-day job and permits are an additional $200.

Central heating and cooling systems have an outdoor condenser and an indoor furnace.

Horizontal draft  Central Air and Heat system with the furnace in the attic

Outdoors Central Air


The outdoor Condenser is usually placed on the side of the house on a poured cement pad- it is important that the condenser is level and be raised off the ground on brackets to increase air flow. In condos, where there is no room to put the condenser on the ground, condensers are put on the roof (with a crane).

Condo Condenser on roof

These Condenser units cool the warm refrigerant gas by squeezing it until it becomes a liquid in the condenser coils. This chilled refrigerant is sent back to the house to cool. Condensers run on electricity and need a 220 V outlet to connect to. Condensor size is measured in Tons. The general rule of thumb is 1 ton for every 600 sqft of living space.

Indoors Central Air

The chilled refrigerant is sent straight to the evaporator coil inside where it cools the air.

A frame Evaporator Coil- notice the drip pan underneath it, when the air cools water condenses on the evaporator coil, runs down, and collects in the drip pan.

The Evaporator coil has a dehumidifier side effect while it is cooling the air. When air with high moisture content rapidly cools water condenses on the evaporator. Some Central Heat and Air systems have UV lights to kill any mold that can grow if the evaporator isn’t properly vented.

The Blower in the furnace circulates the cooled air through the ducts.


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