Often you hear someone say "the house called for a 95,000 btu furnace but the contractor put in a 125,000 btu just to make sure we have enough heat or; it called for a 3 ton air conditioning system but the contractor installed a 4 ton just to make sure we had enough cooling. This is called shooting yourself in the foot. Moving enough air over the heating or cooling surfaces of this furnace or air conditioner will drastically change the static pressure in your ductwork preventing the heat or cold from getting to the living space quickly. This means the burner, or A/C compressor that is already burning more energy than the house needs, is now also running longer. To lower static pressure, a properly trained contractor will evaluate the duct system and its components to see what improvements can be made to get the static pressure to the design level of the heating and cooling system.
If we don't test, you don't know. Because static pressure affects the performance of a heating and cooling system, it can easily be compared to the way cholesterol affects the performance of blood vessels and the longevity of the heart. Static pressure is used to measure the resistance in a duct system created by the ductwork itself, the filter, the evaporator coil, return ducts, and the grills. The blower must overcome this resistance for it to push the proper amount of air at the optimum speed to satisfy your house.
Static Pressure plays a major role in how well a heating and cooling system performs. When there's more resistance (high static pressure), airflow from the fan decreases, and so do the rated BTU's and efficiency of a heating and cooling system. In fact, high static pressure can easily turn a 94% AFUE furnace into a 50% AFUE and a 13 SEER cooling system into a 7 SEER system. This point illustrates the importance of checking the duct system for static pressure. To lower static pressure, a properly trained contractor will evaluate the duct system and its components to see what improvements can be made to get the static pressure to the design level of the heating and cooling system.
The manufacturers, and hopefully the installer, take great pains to seal their refrigerant systems from leaks. A system only runs at its advertised efficiency when the coils and filters are clean and the refrigerant charge is correct. The minute your system starts losing refrigerant the efficiency rating plummets. This happens because the compressor has to work harder to cool the same area so it has to run longer. Unfortunately, all of the components and the labor that goes into cooling your house are provided by humans. No matter who the manufacturer is, when you build a million anythings, you are bound to make a mistake. The bottom line is: if you need refrigerant, you have a leak — plain and simple. For the sake of your comfort, your utility bills, the longevity of your system, and the environment, leaks need to be addressed before adding more refrigerant.