Hvac automated 7 system best recommendations am i gonna need 2 big brother and expansion? i haven need for more Outputs
The rule of thumb for system design is to keep the brain near the muscle. If you load up a central T3 with expansion IO scattered all over a building, you are vulnerable at a single point to network cabling problems.
In a major mechanical room where all the IO is coming into a single cabinet, using a T3BB plus some T3E expansion modules is fine. The risk is low because the wiring stays within that one enclosure. However, for distributed equipment like VAVs or fan coils, you should always go for dedicated T3-TB controllers.
Doing a quick check on the pricing, them T3E-886 expansion module is about $150, while a T3-TB programmable controller is only $153. For an extra $3, you get a local CPU, the ability to run Control Basic, and two RS485 ports. If the network goes down, the T3-TB keeps the room running locally.