Air Conditioning / What Size is the Right Size?

Air Conditioning

Finding out will require an interview, an evaluation and a Manuel J load calculation.

The interview:  The right size air conditioning depends on the indoor temperatures the people living in a home want to maintain.  The right size heating and air conditioning system will also depend on how different people use their homes. Some homes are used to entertain larger groups of people. Some homes will have many rooms that are seldom occupied. Other homes will have both. Without talking to the people who use the home every day, it’s just not possible to size and customize an air conditioning system that will best meet their individual heating, cooling, or indoor air quality needs.

The evaluation: Once the needs of a home’s occupants have been considered, it’s time to consider the specific needs of the home.  Using a generalized “rules of thumb” to size an air conditioning system here in the San Marcos, Buda, Kyle and New Braunfels areas of Central Texas is very much like going to Las Vegas and betting a few thousand dollars in a slot machine … it be your lucky day … but probably not.

A home evaluation includes gathering attic insulation values, type of foundation, type of windows, window location, window solar gain, exterior sheathing, kind of roofing material, attic ventilation, wall insulation, number of fireplaces, number of occupants, and more. The evaluation gives the HVAC contractor the information needed to determine how quickly a home will transfer heat from outside to inside in the summer and from inside to outside in the winter.  It also tells the HVAC contractor how much heat is generated inside the home.  All these factors are needed to help determine a buildings’ “heat load”.  The right size air conditioning system depends on knowing how well or poorly a building is sealed, insulated and vented.

Manuel J Load:  Once the needs of the people living in a home, and the needs of a building are known, the right size air conditioning system can be calculated using the specific weather conditions for a specific location.  Manuel J is a complicated set of scientific formulas developed and designed specifically for calculating the proper size of air conditioning system need to heat and cool a home. Modern software has made the process quick, simple and easy.

The most precise calculations will only insure that an air conditioning system is no too big and not too small to maintain indoor temperatures and humidity under a single outside load condition.  Normally that outdoor load condition is based on a worst case scenario. Here in the San Marcos, Buda, Kyle, and New Braunfels area of Central Texas, that worst case is 100 degrees at high noon and full sun.  Single speed (single capacity) air conditioning system that can’t adjust for changes in outdoor conditions are considered “the right size” even though they are (technically) too big most of the time.

The right size air conditioning system is one that would run at different speeds in order to more closely match the ever changing indoor and outdoor load conditions of the home. These two speed and variable speed systems operate much like an automobiles cruse control.

Las Vegas or Manuel J … you decide.   If your decision is Manuel J, an AirOne professional will be happy to help and explain your options and the added benefits of two speed and variable speed air conditioning systems.

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