Choosing the rightly sized unit is of great importance for providing good amount of comfort. To determine the correct size of the HVAC unit that your home would require, the first step is load calculation. Load calculation is important to find out the heating and cooling requirement of your home. Depending on that an HVAC contractor will be able to suggest you the correct size of the unit.
The HVAC unit should be installed in such a way that the static air pressure drop across the handler is within the Manufacture and Design specifications so that the unit has the capacity to meet calculated load needs.
There should be sealed supply ductwork so that there is proper airflow within the rooms. At the same time, an HVAC unit will have to be installed with a return system sized to provide correct return air flow.
The return air duct should also be sealed so that proper air flow is provided to the fan and no polluted air is able to enter the HVAC system.
There should be balanced air flows between supply and return air systems so that neutral pressure can be maintained within the home.
The HVAC unit needs to be installed in such a way that there is almost negligible duct air temperature gain or loss between the air handler and room registers and between return registers and the air handler.
The HVAC unit must be properly charged with refrigerant so that it can function properly.
It is pertinent that the HVAC unit has proper burner operation and proper draft.