SIEMENS 550-400 TEC Controller - Cooling Only BRAND NEW The Siemens 550-400 is an Actuating TEC (Terminal Equipment Controller), cooling-only unit used in HVAC terminal box or VAV-style applications, typically as part of a Siemens TEC/ATEC building controls system. It is designed to control cooling actuators/dampers in 24 Vac systems and is usually paired with separate Siemens room sensors and other TEC controllers in the same product family.? What it is The 550-400 is identified by resellers and Siemens parts listings as a ?Siemens 550-400 TEC Controller Cooling Only? or ?Actuating TEC,? placing it in the TEC/ATEC terminal equipment controller line rather than general-purpose PLCs or motor contactors. These controllers are used in building automation for local control of HVAC terminal units (like VAV boxes or fan-coils) under a Siemens Building Technologies front-end.? Typical application and system role In a typical installation, this controller drives cooling-only actuators or dampers on a terminal unit while communicating with a supervisory system or network of TECs. It usually works alongside: a Siemens room temperature sensor, airflow/pressure or auxiliary sensors (depending on the exact TEC variant), and other TEC models (such as 540?100N or 550?495 series) handling heating, reheat, or extended I/O.? Electrical and control characteristics (family-level) Siemens TEC family documentation describes similar terminal box controllers as 24 Vac devices, with power requirements typically around 19?28 Vac and low VA draw, plus additional VA per digital output when driving loads. Controllers in this TEC line generally provide a mix of analog inputs (for room and auxiliary temperature or velocity sensors) and multiple 0?10 V analog and 24 Vac digital outputs for fans, valves, or dampers, managed via PID-based control algorithms for stable temperature/airflow control. We are wholesaler/liquidators. We bought this in a lot of new items to resell. We are counting upon you to know what you are buying and if this item will suit your needs. Please only purchase this if you agree to those terms. *** PLEASE NOTE! Our store buys and sells a variety of new and used electronics, instruments, tools, antiques and many other items. We do our absolute best to thoroughly test all our merchandise and accurately describe and depict any flaw or defect we find. SHELF: FA-C SA