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What is the Central Control Unit and What Does It Do?

Why is the Central Control Unit So Important?

Every 75F building implementation must have at least one Central Control Unit (CCU). The CCU is critical to the value of data aggregation and cloud computing that 75F provides. The CCU is the front-end of the system on-site, serving as a wireless gateway to the cloud. The CCU is a removable tablet with wireless communications. It replaces a standard thermostat and easily installs, connecting to low-voltage relay contacts that activate the equipment’s heating, cooling and fan signals. The CCU provides a primary user interface for building management including mobile pairing, configuration and settings, zone status, schedules, sensor input graphs and much more.  

The Gateway

The CCUs most important function is that it acts as an aggregation point for all of the terminal units (i.e. Smart Node, Smart Stat). Using a 900 Mhz wireless mesh network, the CCU will send and receive control signals to and from the terminal devices. 

If you want to change the schedule of a zone, you would login to Facilisight from wherever you are and make the change. That change would be routed through the cloud service and down to the CCU where the signal will be converted into a 900 Mhz mesh network communication which will be sent to the zone controller. 

Components - Hardware

There are two hardware components that make up a CCU.

  1. Tablet - Connects to WiFi and sends data to the cloud wirelessly. This is also the on site user interface where scheduling and configuration can be done. 

  2. Control Mote (CM) - This acts as the I/O board and 900 Mhz mesh network aggregation point for the CCU. All terminal devices will be routed to the CM which will then be pushed to the Tablet through a USB connection. The CM will also take control messages from the tablet through the USB connection to be sent out to the terminal units on the mesh network.

Together as the CCU, these devices can control a piece of single- or two-stage HVAC equipment. In most applications, the CCU controls the central piece of equipment for a group of zones (e.g. Controls the RTU in a VAV system). In other applications, the CCU acts solely as a gateway. In other applications yet, the CCU can act as a single zone controller for a piece of equipment. 

Matt Blount