Orion System VCC-X Controller - Manual (Page 55)

VCC-X Controller Technical Guide
SEQUENCE OF OPERATIONS
55
Supply Fan & Occupied/Unoccupied Operation
Supply Fan Operation
Anytime the Supply Fan is requested to start, a 1 minute minimum off
timer must be satisfi ed. If the timer is satisfi ed, the Supply Fan relay
is activated while all other outputs are held off until their minimum
off timers have been met.
Upon going into the Occupied Mode or upon power-up, the controller
will initiate a user-adjustable Fan Starting Delay to provide a
staggered start for systems with several HVAC units.
In Fan Cycle Mode or when going unoccupied, the Supply Fan is held
on for 2 minutes after the last stage of Heating or Cooling stages off.
Purge Mode
When going into Occupied Mode, an optional “Purge Mode” is
initiated. The fan runs with the Economizer closed, and all Cooling
and Heating is de-energized. The length of the Purge Mode is user-
adjustable.
Occupied Mode
The Supply Fan can be confi gured to run continuously (default) or
to cycle with Heating, Cooling, or Dehumidifi cation.
Unoccupied Mode
The Supply Fan will cycle on a call for Heating, Cooling, or
Dehumidifi cation.
HVAC Source Confi guration Options
The VCC-X Controller can be confi gured to have various HVAC
Source options that will determine the mode of operation (Heating,
Cooling, or Vent Mode) of the unit. The following are descriptions
of those options.
Space Temperature —Typical selection for CAV
recirculating units.
Return Air Temperature —Optional selection for CAV
recirculating units.
Single Zone VAV —Selected for a Space Temperature
controlled Single Zone VAV application.
Outdoor Air Temperature —Typical selection for 100%
Outdoor Air (MUA) or High Percentage Outdoor Air units.
Supply Air Temperature —Selected for Cooling Only
VAV units with optional Morning Warm-Up.
Supply Air Tempering —Selected for Cooling Only
VAV units with optional Morning Warm-Up.
Space Temperature with High Outdoor Air % — Pro-
vides Space Temperature (instead of Outdoor Air Tempera-
ture) control of 100% or high percentage Outdoor Air units
by tempering the air during the Space Vent Mode of opera-
tion to prevent dumping of hot or cold air into the space.
HVAC Mode Set by Remote Contact Input — Provides
for wet contact closures to force the unit into Heating, Cool-
ing, and Dehumidifi cation modes. If this option is selected,
it applies to all three modes, and all three modes will only be
initiated by these contact closures.
Occupied/ Unoccupied Mode of
Operation
The VCC-X Controller can utilize several methods for determining
the Occupied Mode of Operation. These are as follows:
Forced Schedule
Remote Forced Occupied Signal
Internal Week Schedule
Push-Button Override Signal
Forced Schedule
The VCC-X Controller can be forced into the Occupied Mode by
inputting a Forced Schedule from any operator interface.
Remote Forced Occupied Signal
This Forced Occupied input can be used in place of, or in conjunction
with, the internal VCC-X Schedule. When this wet contact input
closes, it will force the VCC-X Controller into the Occupied Mode.
When the Remote Forced Occupied Signal is removed, the controller
will revert to the Unoccupied Mode of operation, or if an internal
VCC-X schedule is also being used, it will revert back to the current
scheduled mode.
Setting the Internal Week Schedule to ‘0’ will cause the controller
to only look for the Remote Forced Occupied Signal for Occupied/
Unoccupied commands.
Internal Week Schedule
An Internal Week Schedule, which supports up to two start/stop
events per day and allows scheduling of up to 14 holiday periods
per year is available for determining Occupied and Unoccupied
Schedules. It also allows for daylight savings confi guration.
Unoccupied Operation
Uses Unoccupied Setback Offset Setpoints for heating and cooling
calls. If Unoccupied Setback Setpoints are left at the default 30°F,
no Unoccupied Setback operation will occur and the unit will be off.
The Outdoor Air Damper will be closed except if the unit is in
unoccupied Economizer Free Cooling mode.
If there is no call for Heating or Cooling, the unit will be off.