Orion System VAV/Zone Controller - Manual (Page 20)

Technical Guide
VAV/Zone Controller 20
The integral also has an effect on the auxiliary heating relays. See the
Heating Mode section for a description of this effect.
On pressure dependent terminal units, the damper position is maintained
to within ± 3% of the calculated position. No attempt is made to posi-
tion the damper exactly on the calculated position. This reduces wear
and tear on the actuator gears and motors and the amount of airflow
involved is not affected by that small amount of damper error.
On pressure independent terminal units, the airflow is maintained to
within roughly 3% of the terminal unit size constant but no tighter than
16 CFM on the smallest terminal units. The actual control window is
based on the formula:
Window = Terminal unit size X Square Root (1 / 750)
Where Terminal unit size refers to the total rated CFM of the
terminal unit.
This sliding window allows the control to be much tighter on the smaller
terminal units than can be achieved on the larger terminal units as far as
CFM readings. On a large terminal unit, 25 CFM may not be noticeable
but on a small terminal unit, 25 CFM may be more than the minimum
airflow setting for the space.
If the pressure sensor is disconnected or fails on a pressure independent
terminal unit, the controller automatically reverts to pressure depen-
dent operation and generates an alarm to alert the user that a failure has
occurred.
On either type of terminal unit, a space sensor failure will force the
damper to position itself to the 50% position and it will not change until
the sensor is repaired or replaced.
Tenant Override Logs
If you require tenant billing for push-button override usage, a MiniLink
Polling Device must be installed on each local loop. The MiniLink Poll-
ing Device has the ability to track the amount of override time gener-
ated by each space sensor equipped with push-button override.
Storing and retrieving these logs requires a dedicated computer running
the Prism front-end software program. No other method exists for re-
trieving these logs. That means that all of your units will be connected
together on the communications loop and the loop will be terminated at
a CommLink II device connected to an on-site computer.
Warning: This computer must be on 24 hours a day 7 days a
week running the Prism software in order for tenant
logging to be tracked.
The tenant logs are kept on the dedicated job site computer’s hard drive.
The only limitation to the number of logs stored is the capacity of the
hard drive on the computer they are being logged too.
Note: For proper time and date stamping of the tenant log, you
must configure the air handler to broadcast the time so
that the VAV/Zone Controllers can read it and use it in
their tenant and trend logs.
Zoning
Description
The Orion system can be configured to operate as a true zoning system
with the addition of a MiniLink Polling Device. The MiniLink Polling
Device acts as a loop manager receiving information from the VAV/
ZONE controllers, interpreting this information, and then sending a heat,
cool or vent signal to the VAV/CAV Controller.
Zone Polling
The MiniLink Polling Device must be configured for zoning operation
from the System Manager, Modular Service Tool or Prism Computer
front end software. During the setup and programming, the user is re-
quired to enter the last VAV/Zone address on the loop. Once config-
ured, the MiniLink Polling Device begins polling each VAV/Zone con-
troller for its temperature and setpoint information. A zone poll cycles
through all configured zones in one pass, without interruption.
The following is a list of status information required by the MiniLink
Polling Device to correctly perform its HVAC Mode calculations.
•
Zone Temperature
•
Current Cooling Setpoint
•
Current Heating Setpoint
•
Current Zone Operating Mode Status & Alarm Conditions
A zone is considered MISSING if it fails to respond to 5 consecutive
polling requests. A Missing Zone alarm can be generated in less than 2
minutes. This alarm can generate an alarm callout to maintenance or a
supervisor if the system has been properly setup ( See Alarm Reporting
Section ).
Zone Voting
If a zone has been configured for the VOTING mode, the MiniLink
Polling Device will perform the following tests based on the data re-
ceived during the zone polling operation. These tests insure that only
properly operating zones can have an effect on the HVAC Mode calcu-
lation.
•
The zone has not been reported as MISSING.
•
The zone is not currently undergoing Damper Calibration.
•
The Zone Damper has not failed driving Open or Closed,
and it passed Calibration.
•
The Zone Temperature readings are between 40 °F and
105 ºF
•
The Zone Cooling Setpoint is between 55 °F and 105 ºF
•
The Zone Heating Setpoint is between 48 °F and 99 °F
•
The Zone has not been declared Maverick by the MiniLink
Polling Device.
•
The Zone has been configured as a VOTING zone.
Sequence Of Operations