80/20 System

80/20 systems can be a variable make-up air unit, a total-building heat unit, or a combination of both. By recirculating air, this system provides the most efficient building heat system.


One unit can handle multiple and varying exhaust loads as a variable, make-up air unit using the 80/20 System. This system offers constant discharge airflow but varies the amount of outside air introduced to the building. With the use of the 403M or the 404M space-temperature control system, the unit can be a complete building heating system for either fixed or variable exhaust loads.


The 80/20 System supplies at least 20% outside air to the building and mixes with re-circulated room air at a maximum of 80%, without the return air re-circulated through the burner. A building-pressure switch controls the modulating-burner bypass and return-air dampers introducing more outside air as the building’s exhaust load changes. The varying exhaust-air loads automatically and continually adjust the amount of make-up air introduced into the system.

All Rupp Air direct fired systems are provided with terminals to integrate operation with the building exhaust system.

CFM Range

N/A 34,000 - 66,000

BTU/hr Range

N/A 1,469,000 - 9,440,000

Motor HP Range

N/A 15.0 - 50.0

External Static Pressure (in w.c.)

N/A 0.0 - 2.0