Patent ID: 8892797

Claim:
A heating, ventilation and air conditioning (HVAC) data processing and communication network, comprising: an active subnet controller and an inactive subnet controller coupled to a data bus, said active subnet controller configuring and monitoring a network and implementing heating, cooling, humidification, dehumidification, air quality, ventilation, and other functional algorithms wherein said inactive subnet controller listens to all messages broadcast over said data bus and updates said inactive subnet controller's internal memory to match that of said active subnet controller; an HVAC demand unit coupled to said data bus, said HVAC demand unit providing an HVAC service in response to a command from said active subnet controller; and a functional block within and specific to said HVAC demand unit, said functional block configured to respond to a message received via said data bus to cause said HVAC demand unit to enter a hard disabled state or a soft disabled state, wherein in said hard disabled state said HVAC demand unit does not provide a service or broadcast messages via said data bus, but continues to receive messages via said data bus, wherein in said soft disabled state said HVAC demand unit continues to receive and respond to messages over said network but does not provide a service.