Orion System VCM-X Modular E-BUS - Manual (Page 67)

VCM-X Modular E-BUS Controller Technical Guide
SEQUENCE OF OPERATIONS
67
Overrides and VAV/Zone System
Force Modes or Overrides
Warning: No equipment protection is available during the
Force Mode of operation. That means you could start a compressor
without running the Supply Fan or could create other conditions
that WILL damage the equipment. WattMaster Controls assumes
no responsibility or liability for the misuse of Overrides that cause
damage to the equipment!
The VCM-X E-BUS Controller relay and analog outputs can be user-
overridden if the Modular Service Tool or the Prism Computer Front-End
Software is used. The System Manager cannot be used for these Force
Modes. The Modes of operation for the relays are as follows:
0 = Normal Operation
1 = Forced ON
2 = Forced OFF
The Analog Outputs are Forced when you specify a value between 0.0
and 10.0 VDC. To cancel the Force Mode, you must enter a value less
than zero, such as -1.0 VDC.
When the Analog Outputs are Forced, the display on the Modular Service
Tool or Prism program can be interpreted as the actual voltage. During
normal operation, the display indicates the percentage signal applied
based on the user-defi ned voltage limits. For example, if you defi ne a
2.0 VDC to 10.0 VDC range, then 50% would be 6.0 VDC instead of
the 5.0 VDC applied when the range is 0.0 VDC to 10.0 VDC.
As previously mentioned, Force Modes can only be activated when
using either the Modular Service Tool or the Prism Computer Front-
End Software. Furthermore, the Override condition can only remain in
effect as long as one of these Operator Interface devices is connected
and communicating with the VCM-X. That means that you cannot
Force an Override condition and then walk away from the equipment
with the Override still active. The loss of communications, removal,
or shutdown of the Operator Interface will automatically terminate the
Override within 10 minutes. This protects the equipment and prevents
an Override condition from remaining active indefi nitely, resulting in
ineffi cient or dangerous operation of the equipment.
VAV Terminal Unit Controller
Compatibility
The VCM-X E-BUS Controller is designed to communicate with Orion
VAV/Zone Controllers. The VCM-X E-BUS can be confi gured to broad-
cast its Internal Schedule, Time, and Date, Fan and Heat Status, and
Supply Air Temperature. The VCM-X E-BUS can also broadcast Force
to Max or Force to Fixed Position during Morning Warm-up. The Orion
VAV/Zone Controllers broadcast Push-Button Overrides from Unoccu-
pied to Occupied. The controllers can also generate Unoccupied Heating
and Cooling calls to the VCM-X E-BUS Controller based on Setbacks.
If you are using another manufacturer’s VAV Terminal Unit Control-
lers, the VCM-X E-BUS Controller can activate a relay to inform the
VAV/Zone Controllers that the VCM-X E-BUS Controller is operating
in Warm-up Mode. No other information can be passed between the
VCM-X E-BUS Controller and the other manufacturer’s VAV Terminal
Unit Controllers. This means that Overrides or Unoccupied Heating and
Cooling calls cannot activate the VCM-X E-BUS Controller. If you need
any of these capabilities, you must use only Orion VAV/Zone Controllers
for controlling all of your VAV Terminal Units.
VAV/Zone System
When the VCM-X E-BUS goes into the Occupied Mode, it initiates
Morning Warm-up if the Return Air Temperature is below the Morning
Warm-up Target Temperature Setpoint. During Morning Warm-Up, the
VAV/Zone Controllers will modulate open if the Space Temperatures
are too cold. They can also move to their Maximum Airfl ow or Fixed
Airfl ow Position Setpoint if they receive this broadcast from the VCM-
X E-BUS Controller. Once Morning Warm-up has been satisfi ed, the
VCM-X E-BUS enters the Cooling Mode and the VAV/Zone Controllers
will modulate to satisfy their Space Temperature Setpoints. If the Space
Temperature falls below the Heating Setpoint, staged or modulating
Reheat can be activated to warm the space.
Communications between the VCM-X E-BUS and the VAV/Zone Con-
trollers are handled by the MiniLink Polling Device. Alarm Polling and
Tenant Overrides are also monitored by the MiniLink Polling Device.
Tenant Overrides are overrides generated by the Space Temperature Sen-
sor’s push button. The MiniLink Polling Device records the start and stop
times and total run times of the overrides on a daily and monthly basis.
A computer running Prism Computer Front-End Software is required to
retrieve all data acquired by the MiniLink Polling Device.
Zoning System
The VCM-X E-BUS Controller automatically confi gures itself for
Voting Control when the MiniLink Polling Device is installed and is
confi gured as a Voting System. The VCM-X E-BUS Controller sets the
HVAC Mode Enable to the Return Air Temperature Sensor as soon as
communication is acquired with the MiniLink Polling Device. If the
VAV/Zone controllers are confi gured for Voting, the MiniLink Polling
Device totals the Heating and Cooling demands and determines which
HVAC Mode the VCM-X should be in. The MiniLink Polling Device
broadcasts a forced Heating, Cooling, or Vent Mode of operation to
the VCM-X. Once the VCM-X receives the broadcast to set the HVAC
Mode, it operates as previously described in the VCM-X Sequence of
Operations. If communications are lost, the VCM-X returns to its own
control and will maintain the HVAC Mode Enable Setpoints by using
the Return Air Temperature Sensor as the Controlling Sensor.