The answer to 'why is my replacement' is that there are several common reasons why a replacement HVAC system may not be working as expected. Some of the most common issues include improper sizing, incorrect installation, or a malfunctioning component. It's important to diagnose the specific problem before attempting any repairs.
If the replacement system is not cooling or heating your home effectively, it could be due to an undersized unit that cannot adequately handle the cooling/heating load of your home. Alternatively, issues with the ductwork, refrigerant levels, or electrical connections can also cause problems. In some cases, the new system may simply need to be recalibrated or adjusted to work optimally in your home.