Opticlimate PlenumboxOverview The Opticlimate Plenumbox is a strong insulated case, which you can install at the back of the Opticlimate (OC) closed loop system. The Plenumbox allows you to install the OC outside the grow room and with a 3 way valve you can split the capability of the OC climate system into 2 separate grow rooms. The Plenumbox is delivered with 4 pre cut holes. Only attach the right flange size to secure the ducting where it's needed. The Plenumbox is