Comfort, convenience, confidence. The Zone Control Unit (ZCU) from Siemens Building Technologies, Inc., is an exclusive, patented, pre-assembled variable air volume (VAV) system. ZCUs are delivered to job sites ready for immediate installation. The Siemens ZCU is made to order, engineered to meet 100 percent of all specifications and comes with a two-year parts and labor warranty, which is unmatched in the HVAC Industry.