In the context of HVAC installations, what is the main concern about the size of threaded fittings?

The main concern regarding the size of threaded fittings in HVAC installations relates to pressure ratings. This concern is crucial because the fittings must be able to handle the pressures of the air or fluid they are transporting without leaking or failing. If a fitting is improperly sized, it may not provide a proper seal or support, leading to potential system failures or unsafe conditions.

Additionally, oversized fittings can create turbulence that affects system performance, while undersized fittings can restrict flow and increase pressure drops in the system. Therefore, ensuring the correct size of threaded fittings correlates directly with maintaining appropriate pressure levels and overall system efficiency.