Viconics VWZS Engineering Guide Specifications - Manual (Page 8)

Sequence of Operation
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The Viconics Wireless Zoning System shall operate in the following manner:
1. The VZ7656x1000W Rooftop Unit controller shall determine the mode of operation (heating /
cooling) by analyzing the PI heating and PI cooling demand sent by the weighted VZ7260x5x00W
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). There is a mandatory two-minute delay between switchovers from heating to cooling
to prevent cycling.
2. The Rooftop Unit controller shall also monitor the static pressure sensor and modulate the by-
pass damper actuator accordingly to maintain the static pressure set point.
3. The Rooftop Unit controller shall monitor, return air temperature. If the high temperature limit or
low cooling temperature limit occurs, the Rooftop Unit controller will shut off heating or cooling to
prevent damage.
4. The Rooftop Unit controller shall monitor the outdoor air temperature and send the value to the
zone controllers to allow outside air lockout conditions at the zone level.
5. The VZ7260 zone controller(s) shall send the actual PI heating or PI cooling value multiplied by
the weight reduction factor (if necessary) to the Rooftop Unit controller.
6. The zone controllers shall modulate the local VAV damper to maintain the set point temperature.
Using the integrated PI algorithm, the controller will determine if heating or cooling is required. If
the particular zone has auxiliary reheat enabled, the auxiliary reheat (duct furnace and/or
perimeter heater) will be used if necessary. If the Rooftop Unit is in cooling mode and supplying
cold air and a particular zone requires cooling, the damper will modulate to supply the duct
furnace enough air to heat to try and attain the heating set point.
7. The zone controllers will cycle (on the LCD screen) between outdoor temperature, actual Rooftop
Unit occupancy and actual Rooftop Unit heating/cooling mode.
8. In case of a loss of network, the RTU unit will continue to control the Rooftop Unit based on the
return air temperature.
9. The VWZS can be integrated to any BACnet MS_TP or BACnet_IP DDC central workstation with
the addition of the Viconics Wireless Gateway (VWG-50-IP-5000 or VWG-50-MSTP-5000).