How do I install this on an existing electrical box

this part will not be compatible

Key Benefits Efficient Auto Changeover: Automatically switches between heating and cooling modes based on ambient demand to maintain consistent setpoints

It is designed to be threaded onto an existing Emerson Alco TRAE+ series valve body during routine HVAC repair or maintenance

though you should always verify the actuator stroke matches the 3/4-inch travel of the 599-03204

Reznor 211763 Vent Assembly L99H008 How do I install thisThe Reznor 211763 Vent Assembly is a factory engineered horizontal vent combustion air terminal kit specifically designed for Reznor UDAS and UDBS unit heaters. Supporting heater capacities from 150,000 to 400,000 BTUs, this assembly facilitates a clean horizontal wall termination for concentric venting systems. By integrating both the exhaust outlet and combustion air intake into a single penetration, this kit simplifies the installation process and