Air Conditioning Systems

air conditioning system

The basic Air conditioning cycle is illustrated above.  Refrigerant is pumped by means of a compressor through the system.  During its travel in the dwelling (indoor) portion of the cycle it is forced through a restriction at high pressure, the resultant drop in pressure allows it to evaporate in the evaporator coils where it absorbs heat from the airflow surrounding the coils (upper left).  Typically the evaporator coil is mounted above the heat portion of your forced air furnace and the air is drawn from the house and circulated by the blower motor and ductwork  already present.

The compressor located out of doors in the condensing unit returns the heated refrigerant gasses to a liquid high pressure state as it pumps them through the condenser coils where another fan passes air over the coils to dissipate the heat given off during the condensing cycle into the surrounding outdoor air.  The high pressure liquid gas is returned indoors to the expansion orifice and the cycle is repeated.

The Heat Pump

Heat Pump
The heat pump  is basically an air conditioner in reverse.  Shown above in the 'heat' mode it  simply transfers heat from outdoors that is picked up by the evaporation process of the refrigerant exactly as above in the AC diagram.

The obvious difference is that this evaporation occurs outdoors and the condensation process occurs indoors where it emits heat, thus warming the home.  This process may seem slightly counter-intuitive; how can you pick up heat from the cold outdoors?  This is acccomplished by the 'engineered' temperature/pressure properties of the refrigerant and the physics of evaporation itself.

In the summer the heat pump operates as a conventional air conditioning unit simply by reversing the flow of refrigerant.

The heat pump will have some additional hardware associated with its operation, including bypass valves, a reversing valve, condensing/evaporator coils that are designed to perform both functions, and an auxillary heating coil (electric) for those times when it simply can not pull enough heat from outdoors to satisfy your comfort needs.
It will also include many of the components associated with any forced air heating - cooling system.  These would include the ductwork to distribute the air, a blower fan to propel the air, filters and thermostats.

Why wasn't my AC operated during the Home Inspection?

During the winter season, cold ambient temperatures can substantially thicken ('gel') the outdoor compressors lubricants.  Under these conditions operation of the compressor, as in running the air conditionng, can damage the compressor through lack of lubrication.  As guests and not owners, we are obligated to refrain from doing anything that may damage the property or any of its systems.

The general rule is that we do not operate the AC when ambient temperatures are below 65 degrees fahrenheit.

If the inspected property has a heat pump then the operation of  AC mode is feasible simply because the compressor has already (and is designed to) operate in heat mode during cold ambients.