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1A) Initial Design Criteria Considerations
The scope of this document is not intended to be a resource or white paper on VAV zoning system design.
There are many good resources available on the subject of VAV zoning systems and their associated
advantages and disadvantages. Please consult these resources for further information on this subject.
It is the responsibility of the designer and installer to ensure the following considerations are met:
•
Size the installed equipment for properly calculated heating and or cooling peak loads. There are no
advantages to over sizing the system’s capacity to more than what is required as this simply leads to
short cycling of the equipment during small load periods.
•
Properly size and layout all ductworks including the by-pass damper according to local codes and
standards in effect.
•
Properly size the capacity of the zones according to the actual requirements of the room. Using
square footage calculations only can create situations where the installed total deliverable load may
be insufficient for the actual intended use of an area. Conference rooms, computer rooms, cafeterias
or other rooms where large gatherings occur would be a prime example of this scenario.
It is not the mandate of the zoning control system to correct for wrong initial mechanical layout and or load
calculations of the mechanical equipment. The control system will attempt to deliver the loads required by
master demanding zones by distributing the total available capacity of the installed equipment to the
required demanding areas. If the equipment is undersized for the required peak loads, the control system
will distribute the available capacity according to the priorities requested hence making most of the areas
comfortable.
Proper planning and design will always result in a job site being up and running faster with less service
calls during the initial occupancy period.
1B) Scalability and Limitations
The system is fully scalable in terms of number of Zone thermostats and RTU thermostats used on the
same network layer (BACnet MS-TP or Wireless models).
Wireless thermostat systems overview:
(SA) Stand-Alone systems.
There are no supervisory devices installed in this configuration.
In this application, the VZ76xx thermostat(s) are the network coordinators to their own system. I.E. they are
the network masters for each VZ72xx thermostat reporting to them. Each VZ76xx RTU thermostat and it’s
associated VZ72xx zone thermostats use the same PAN ID and channel. The range of PAN ID on all
thermostats to use is 251 to 500. This range is reserved for stand-alone (SA) system operation.
Smallest System Supported
Largest System Supported
Number of Zones
Number of RTUs
Number of Zones
Number of RTUs
Single network of 127
nodes maximum
1 ZN reporting to
1 RTU Minimum
63 ZN reporting to
1 RTU Minimum
There are no supervisory devices installed in this configuration. The system fully operates in stand-alone
mode.
