Retrofit of an old axial fan in a theatre. After years of operation, the replacement of the entire fan became urgent after one blade was broken. Due to the location of the equipment room in the basement, replacing the bulky fan became a challenge. For this reason it was absolutely necessary for the customer that the replacement would be much easier in the future. The new ECFanGrid system with a volume flow of 130,000 m³/h was a good choice as two people can handle all components. The installation was carried out via normal stairs and lifts to bring the material to the site. Due to the structural conditions, a service door was integrated instead of a bulkhead plate. This also reflects the flexibility of the ECFanGrid retrofit system.