Have Your Home Properly Sized When Buying a New Air Conditioning System

May 15, 2018

Many Brisbane homeowners mistakenly think that the bigger and more powerful a central air conditioner is, the better it will cool your home during hot and humid weather.  That’s not the case. Neither is it enough to measure the square meters in your home to determine the size of your air con.

Many factors affect the efficiency and selection of a properly sized central air conditioning system, such as the height of your ceilings, the type and thickness of insulation and the number of windows, especially those with direct sunlight. Although you may be aware of a simple rule to calculate how many BTWs (British Thermal Units) your home requires for proper cooling, a better and more complex process used by professionals called Manual J will more accurately determine the size of your new air conditioning unit.

What is Manual J?

Measure Your Home Properly When Buying a New Air Conditioning SystemA manual J calculation involved a detailed analysis of your home’s central air conditioning needs. There are two types: a whole house load calculation and a room-by-room load calculation. A whole house load calculation determines the amount of cooling needed for an entire residence and includes:

  • The heat transfer between walls and through your concrete slab
  • The number of windows and their efficiency rating
  • Type and amount of insulation
  • Type of ducting and its location
  • The number of people living in your house
  • Number of skylights, if any
  • What type of lighting you have

Several other factors are also included in the analysis.  Typically, a whole house load calculation is used when replacing only the equipment. A room-by-room-calculation is used when the equipment and the duct system will be replaced or when installing a ductless air conditioning system.

What Happens When a System is Improperly Sized?

Proper calculation is required every time you replace your system because you may have made improvements that affect the amount of cooling your home needs now.  Your old system may not have been properly calculated, either.

A system that is too large will cool your house quickly and satisfy the temperature setting on the thermostat before it can adequately remove humidity from the air, leaving you uncomfortable. It will also short cycle, stressing your system and shortening its life. A system that is too small will also short cycle and run constantly, costing you more in utility bills. Always make sure that you have an an Intagas professional determine the proper sizing before choosing a new air conditioning system.

Contact Mick on 0435 579 094 or send a quick email.

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