Why is a fan control center added to an older furnace when installing a new air conditioner?

The addition of a fan control center to an older furnace when installing a new air conditioner is primarily to address electrical capacity issues and the operational control of the system. In older furnaces, the existing transformer (XFMR) may not provide sufficient volt-amps (VA) to handle the additional load of a compressor contactor. This can result in operational difficulties and potential failures, as the system may be unable to reliably supply the necessary power to both the air conditioning unit and the existing furnace components concurrently.

By including a fan control center, you ensure that there is adequate power supply and control over the blower motor, which is essential for the proper functioning of the new air conditioning system. Additionally, older furnaces may lack a dedicated blower relay, which means the functionality of operating the blower independently of the furnace system could be compromised without this added component.

This makes the fan control center an important upgrade that not only supports the new air conditioning installation but also enhances the overall system reliability.