Global data is data needed by all HVAC controllers in a network, including outside air temperature and electrical demand.

• A. Data needed by all HVAC controllers in a network, including outside air temperature and electrical demand.
• B. Data stored locally on a single controller.
• C. Only historical energy usage data.
• D. Temporary data used during startup.

Answer: (A)

Global data are the pieces of information that every controller in the HVAC network needs to operate in a coordinated way. These shared data points guide how the whole system behaves rather than just one device. Outside air temperature is a prime example because it affects ventilation, economizer logic, and heating/c cooling decisions for all zones. Electrical demand is another key global datum, since it informs load management and pacing decisions across the network so the entire system responds together rather than in isolation.

Data stored locally on a single controller stays with that device and isn’t available or necessary for other controllers to function together. Historical energy usage data is useful for analysis and reporting but isn’t typically required in real time by all controllers to run the system. Temporary data used during startup is ephemeral and specific to the boot process, not something shared across the network for ongoing control.

So the description that defines global data as data needed by all HVAC controllers in a network, including outside air temperature and electrical demand, is the best fit.