Viconics BACnet Zoning System Engineering Guide Specification
Viconics BACnet Zoning System Engineering Guide Spec 1.01 System Description – The Viconics BACnet Zoning System (VBZS) shall provide a simple and efficient demand based system for the operation of changeover bypass or pressure dependent type zoning systems utilizing standard 2 heat / 2 cool configurations, 2 heat / 2 cool with economizer and IAQ, analog heat/2 cool, or heat pump 3 heat/ 2cool.
(4000 feet), repeaters shall be used to ensure proper communication. With repeaters and a BACnet MS_TP supervisory system, the maximum number of nodes on a single BACnet MS_TP trunk can be extended to 128 nodes (of either type of controller). Overall system architecture shall be open-standard based upon Building Automation Control network (BACnet) standard facilitating the future replacement or addition of other system components, quickly and easily.
VZ7656x1000B BACnet Rooftop or Heat Pump Controller The Rooftop unit Controller shall be: VZ7656R1000B: Up to two heating and two cool stages, single fan speed output, 0-10Vdc output for bypass damper or variable-frequency drive (VFD). VZ7656F1000B: Modulating 0-10Vdc heating / 2 cooling stages, single fan speed output, 0-10Vdc output for bypass damper or variable-frequency drive (VFD).
The controller shall be capable of operating the packaged unit even if there is a loss of communication with the zone controllers. The packaged unit will run in heating or cooling based on the return air temperature. If there is no return air sensor installed, the controller shall automatically revert to the internal temperature sensor. Control systems that cannot operate the packaged during a loss of communication with the zones are not acceptable.
The controller shall have the ability to set the programmed occupied schedule time as the time at which the desired occupied temperature setpoints will be attained at the zones. The controller shall automatically optimize the equipment start. This progressive recovery feature can be enabled or disabled. The controller must have a programmable digital input that can be setup for the following functions: 1.
Packaged unit controller model dependent specifications: VZ7656R1000B: Up to two heating and two cool stages, single fan speed output, 0-10Vdc output for bypass damper or variable-frequency drive (VFD). VZ7656F1000B: Modulating 0-10Vdc heating / 2 cooling stages, single fan speed output, 0-10Vdc output for bypass damper or variable-frequency drive (VFD).
BACnet Zone Controller VZ7260 Zone Controller – The zone controller shall be capable of controlling a local VAV analog damper actuator as well as a local duct furnace and on/off or PWM perimeter heater (if necessary). The zone controller shall also be capable of auto-changeover based on the central VZ7656 controller signal. The zone controller shall be capable of modulating the local VAV damper using integrated damper control logic.
The zone controller shall have a binary input that can be configured as follows: BI1 Binary input no.1 configuration (None): No function will be associated with the input. Point can still be monitored through the BACnet network. Default: None (Motion NO): Used in Occupied Mode only to toggle from the Occupied setpoints to the Stand-By setpoints when no motion is detected for 60 minutes at the zone. As soon as motion is detected at the zone, the Occupied setpoints resumes.
Sequence of Operation – The Viconics BACnet Zoning System shall operate in the following manner: 1. The VZ7656x1000B Rooftop Unit controller shall determine the mode of operation (heating / cooling) by analyzing the PI heating and PI cooling demand sent by the weighted VZ7260x5x00B zone controllers. The RTU controller shall supply heating or cooling based on the resulting analysis (highest demand, average of three highest demands or average of five highest demands).
Sequence for economizer on VZ7656E1000B only: The fresh air damper can be controlled through more than one sequence to achieve different control strategies such as free cooling (economizer mode), minimum fresh air control and CO 2 level control. Note: For the sequences mentioned below, the following conditions must be met in order for the sequences to be performed as stated: - Max Pos parameter value must be greater than Min Pos Parameter value.
Economizer Mode and CO2 Level Control If the fresh air damper is to be used for both free cooling and CO 2level control (economizer mode and CO2 level control, but without fresh air measurement station), only the Min Pos, Max Pos, Min CO 2and Max CO2 parameters as well as the free cooling sequence will be active. - The FA Range parameter should be set to 0 CFM.
