16
In order for the PIR logic function to be enabled, the following settings must be enabled at the zone
thermostat.
-
If a local PIR cover is used, be sure to set the (
PIR Func
)
parameter to
ON.
-
If a remote PIR sensor is used on BI1, be sure to set the (BI1) parameter to
Motion NO
or
Motion
NC
.
PIR logic
The PIR function is only used during occupied periods. If occupancy is desired during an unoccupied
period, simply press the local override button (if allowed by the local lockout level configuration). Then local
occupancy will toggle to Override (local occupied ) as per the ToccTimer time value for overrides.
Zone commanded occupied by the RTU schedule
Initial state when no movements
are detected by the PIR sensor
Stand-by
Initial movement detected by the
thermostat ( PIR cover or remote
PIR )
Occupied for 60 minutes after the last movement has been
detected. When the 60 minute timer value has expired and no new
movements have been detected, the thermostat will resume the
stand-by mode.
3) RTU Thermostats VZ7656B1000W Operation
The following information needs to be carefully read and properly understood if proper system
commissioning is to be achieved.
Unlike low end commercial or residential zoning thermostats which typically only use two position demand
or non- demand logic to initialize heating and cooling functions, Viconics VZ7656B1000X uses local PI
zone demand(s) to operate heating and cooling stages. Accurate temperature control in the zones is
achieved by the time proportional control algorithm. This enables performances and control sequences
much closer to what is normally found in DDC application specific control devices.
The operation of the RTU thermostat is linked with the operation of the attached zone thermostats.
Although the thermostat it will operate in a stand-alone mode if the communication network is down, normal
operation of the system as a whole requires that communication with the attached zone thermostats is
functional.
3A) Operation Data Exchanged
Independently of the network layer being BACnet MS-TP or Wireless, the flow of data exchanged between
the zones and the RTU thermostat can be summarized as follow:
Heating and cooling demand data is first exchanged from the ZN thermostats to the RTU
thermostat:
•
Current PI heating demand ( output value is based on PI heating weight configuration )
•
Current PI cooling demand ( output value is based on PI cooling weight configuration )
Each voting thermostat will also calculate is demand values based on their current occupancy mode and
setpoints currently in use: Unoccupied, Stand-By or Occupied.
Based on the control type configuration
(CntrlTyp)
, the RTU thermostat will calculate the resulting heating
and cooling zone demands. (See section 2A) Demand Based Heating and Cooling System.
Proper action to the heating or cooling stages using the time proportional control algorithm is accomplished
based on heating or cooling values.
-
If resulting calculated PI heating demand > resulting calculated PI cooling demand, then ZN
sequence is heating
-
If resulting calculated PI cooling demand > resulting calculated PI heating demand, then zone
sequence is cooling
-
If resulting calculated PI cooling demand = resulting calculated PI heating demand, then zone
sequence stays in last current mode
