When installing your Reznor heater above 6000 feet (1830 meters), a high altitude kit is required. Several DJ20 kits are available and specific to the Reznor heater you are installing.
The 197121 High Altitude Kit is the appropriate kit required for high altitude installation of the Reznor Separated Combustion Fan-Type Heater UDAS-100.
Please note if you are installing your Reznor Heater above 2000 feet the input rate must be derated. This is done simply by adjusting the valve outlet (see installation manual). You do not need to install anything further.