Central Air Conditioners...

Central air conditioners are, undoubtedly the ultimate air conditioning machines compared to any other air conditioners out there.

These units mean serious cooling or heating capacities to your building.

Central air conditioners are also known as year round air conditioners as users will buy central air conditioning unit for continuous conditioning.

The flexibility of cooling and heating capacity, as well as air comfort, these systems can provide, is second to none. Let’s discover more.


Overview of central air conditioners:

Central air conditioners operate in similar manner to other mechanical air conditioners. The operating principle is explained in this page.

There are other auxiliary systems connected to this air conditioner type, but those will be explained in central air conditioners design features sub section.

A single unit (or a pair of condenser and evaporator) will have cooling capacity, ranging from,

  • 12,000 BTU/hr (or 1 ton or 3 kWh or 2.4 hp), to

  • 60,000 BTU/hr (or 5 ton or 16 kWh or 12 hp)

With efficiency ratings from,

  • 13 SEER, to

  • 21 SEER

Note that the specified efficiency ratings are in SEER unit. Hence, the EER figures are higher.

Central air conditioners can both, serve a large space, and do it efficiently.


Design features:

  • Central air conditioners consist of a condensing unit, an evaporating unit, and a blower.

    The evaporating unit comes with a blower, and it is famously known as AHU, or air handling unit.

    AHU and condensing unit are connected together at site, with copper tubes

  • A significant difference between central air conditioning units, compared to other units is, these systems need ducts.

    Otherwise, conditioned air could not be delivered to other spaces within your building.

    In fact, ducts are the secret weapon of your central air conditioner, for air distribution. Of course, ducts has to be sized properly

  • Air conditioner filters either come together with the air handling unit, or can be installed separately within the duct system

  • You can do a major improvement to your air quality with ducted systems.

    It is achieved by mixing fresh air and re circulated air into your house, while expelling some re circulated air, out of your building

  • And hence, dampers are, very important in central systems, to mix air in specified proportions

  • The good thing about central air conditioners are, the installation is not just limited to condensing unit and air handling unit.

    You could also install auxiliary units such as,

    • A humidifier, to increase humidity (normally in cooler seasons)

    • A preheater. Used in cold seasons to heat up fresh air, thus preventing water from the humidifier to freeze up,

    • Auxiliary heaters, to provide better temperature control to each room, and

    • Air quality analysers, to continuously monitor for toxic gases in atmosphere, and shut down the system when toxic gas is present.

      However, this installation is not common in residential units

  • Several condensing and evaporating units can be used together to serve a very large space

  • An excellent feature, most central air conditioners have, is the two stage compressor.

    Such installation is very important in maintaining low operating, and maintenance cost of the compressors, as the compressor can run on a low speed during low loads, rather than shutting down

  • Not only that, you’ll be please to know that AHUs, also comes with variable speed blower motors.

    This setup will save energy under low loads, while maintaining good air circulation, and humidity removal throughout the building

  • Thermostats? Of course.

    Air conditioner thermostats for central air conditioners can be placed in various locations. Either at,

    • The return air duct/s, just before the air handling unit room,

    • Your room/s or,

    • Within the duct itself

    Zone temperature and humidity control can be achieved by automatically adjusting dampers placed before the supply air registers, or by auxiliary heaters

  • A condensate drain from the AHU is a must


User profile:

You can get the most benefit from central air conditioners if,

  • You require continuous air conditioning, for a large and occupied space, or

  • You require air conditioning with continuous supply of fresh air


Installation and setup:

Central air conditioning units are installed in this manner,

  1. Install the condensing unit on concrete foundation,

  2. Install the AHU at the most appropriate location within the building,

  3. Install copper tube between the AHU and condensing unit,

  4. Evacuate system, check for leaks, remove moisture, and charge with correct amount of refrigerant,

  5. Wire the system, and the thermostats,

  6. Check for correct operation of the system,

  7. Install properly calculated duct system, from the air handling unit, to rooms within the building,

  8. Install filters for fresh air intake, and extractor for re circulated air,

  9. Install registers at supply and return ends, and you’re up and ready for central cooling or heating


Service and maintenance:

Service and maintenance for central air conditioners are explained in air conditioning maintenance page.

An additional maintenance activity worth doing, is periodically checking your duct system for crack openings, and unwanted guests – pests.


Pros and cons for central air conditioners:


ItemProsCons
CostLow operating cost, per BTU, compared to other air conditioners. Wins hands downHigh initial cost
Air qualityGood, if the filter is maintained. Duct system allows for fresh air intake and used air dischargeDo you have anything to put here? I don’t have any
MobilityNoneDon’t buy central air conditioners, if mobility is your requirement
Conditioning abilityAble to serve a large buildingDistrict cooling systems can serve a bigger area. However, it is a different arena than residential cooling
NoiseWhat? Noise?None
Stylish lookThe best. You will hardly notice the registersBe sure to have some plants around your condensing unit, as these units are big
StrengthVery good installation strength. RobustNone


Is it for you?

Central air conditioners can be your best air conditioning system if you’re looking into conditioning a large space, with a large number of occupants, or if you need continuous supply of fresh air into your building.



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