Specifications

C E N T A U R U S P R I M E
23
2323
23
6
Minimum On/Off
Trane: Miscellaneous
7
Custom Programming
—
High
Trane: Demand Limiting
8
Manual Operator
Trane: Miscellaneous
9
VAV Air Systems
Trane: VAV Air Systems
10
Chiller Plant Control
Trane: Chiller Plant Control
11
Area Control
Trane: Area
Control
12
Manual Operator
—
Low
Trane: User
-
Low
13
Miscellaneous
Trane: Miscellaneous
14
Timed
-
Override
Trane: Timed
-
Override
15
Time
-
of
-
Day Scheduling
Trane: Time
-
of
-
Day Scheduling
16
Custom Programming
—
Low
Trane: Custom Programming
—
Low
N/A
Rel
inquish Default
Relinquish Default
Note in the “Comments” we have given what the Tracer Summit “Default” was for
the priorities in question. This is informational only, but might help some of you who
were used to an old Tracer system.
Each controllable point in BACnet (that is, an AO or a BO) has a “priority array”
which is generally sparsely populated. Nothing in a particular priority level is specified
by “Null”, which means that priority level is unused.
As an example, consider a warehouse exhaust fan which is turned on and off by a time
schedule at priority 15. In a demand-limiting situation, this point may also have control
at priority 7 (shut down ancillary systems in energy peak situations). But
programmatically, a logic block that detects a fire might want to override everything
and keep the fan on in order to pressurize an area and keep the fire from spreading, so
that might be at priority 2. When control is “released” from the higher levels, the next
lowest control is issued. Hence, after the fire is over, the fan that was overridden ON
might go OFF from its priority 7 demand-limiting shutdown. But if that priority 7
control had been released, then the control descends to the priority 15 time-schedule
control. You have to know what your plant’s priority system is, and what each point’s
capabilities and control options are—this is not a trivial control philosophy!
The “Relinquish Default” value, if any is specified, is the control that is given out to a
point if there is NOTHING in this priority array (that is, all 16 levels of control have
been released). If there is no “Relinquish Default” value, then the point just sits there,
at it’s last control.
Now, before you can control a point object you must first have selected a device
number , a point type/instance, and a priority. Then you can set the control value, and
that value will go into the object’s priority-array. That does NOT mean that control
will be issued, remember, since you may be at a lower priority level than what is
controlling the point right now.