Building Control (Field Installed)
Zone Controller – Application Specific
Variable Volume V. Temperature (VVT) Comfort System - Sequence of Operation
Note: The following is a sample of a typical Sequence of Operation that may be adapted for a
particular project. This is provided as a suggestion on how to write a Sequence of Operation for a
specific project. The VVT Comfort System includes the ability for the operator to select some
different sequences. Consult your Carrier representative if the sample sequence requires
alterations.
4.3.2
Variable Volume/Variable Temperature (VVT) Comfort System - Sequence of Operation
A. Occupied Mode:
1. Fan Operation
If the Fan mode is configured to “ON,” the system fan will operate continuously.
If the Fan mode is configured to “AUTO,” the fan will start with a call for first stage cooling or
heating and continue to operate for 90 seconds after the mode has been satisfied.
2. Cooling Operation Staging Control:
The Monitor will scan all associated zones to collect system temperature demand data. System
mode shall be determined by total number of zones with cooling demands 1.5°F above the zone(s)
cooling setpoint. If the total number of zones requesting heat outnumber cooling demand zones,
the Monitor shall request a system heating mode and all zones desiring cooling shall remain in a
stand alone mode. All cooling zones shall go closed, to minimum position or to supplemental heat
position during system heating mode. With a system cooling demand greater than heat, the
Monitor shall energize the first stage of cooling. All zones desiring cooling shall modulate their
zone dampers open, corresponding to their space temperature demand. Upon a further rise in
space temp of 2.0°F or greater than the cooling setpoint of the reference zone, the Monitor shall
execute a call for second stage cooling. If conditions are being satisfied with first stage only, based
on the Optimized Staging conclusion, if so configured, second stage shall be delayed until
conditions are no longer being maintained by first stage. pon a decline in demand to 1.0°F of the
reference zone setpoint, 2nd stage cooling shall be released. Upon a further decline in demand to
.4°F of setpoint of the reference zone, first stage cooling shall be released. The reference zone is
determined by the largest demand for the cooling mode. The reference zone shall be re-evaluated
during the system cooling mode until all zones have satisfied their cooling demands. The Monitor
shall be capable of reevaluating the system cooling mode, switching to a system heating mode,
based on a configurable system mode reselect time value from 0 to 480 minutes when space
temperature demand is greater for heating.Zones requiring heat shall be capable of independent
supplemental heating during a system cooling mode through hot water valve, fan powered heat or
auxiliary heat sources controlled by the Zone Controller.
3. Heating Operation Staging Control:
The Monitor shall scan all associated zones to collect system temperature demand data. System
mode shall be determined by total number of zones with heating demands 1.5°F below the zone(s)
heating setpoint. If the total number of zones requesting cooling outnumber heating demand
zones, the Monitor shall request a system cooling mode and all zones desiring heating shall
remain in a stand alone mode. All heating zones shall go closed, to minimum position or
supplemental heat position during system cooling mode. With a system heating demand greater
than cool, the Monitor shall energize the first stage of heating. All zones desiring heating shall
modulate their zone damper to maintain space temperature demand. Upon a further fall in space
temperature 2.0°F below the heating setpoint of the reference zone, the Monitor shall execute a
call for second stage cooling. If conditions are being satisfied with first stage only based on the
Optimized Staging conclusion, second stage shall be delayed until conditions are no longer being
maintained by first stage. Upon a decline in demand to 1.0°F of the reference zone setpoint,
second stage heating shall be released. Upon a further decline in demand to .4°F of setpoint of the
reference zone, first stage heating shall be released. The reference zone is determined by the
largest demand for the heating mode. The reference zone shall be re-evaluated during the system
heating mode until all zones have satisfied their heating demands. The Monitor shall be capable of
re-evaluating the system heating mode, switching to a system cooling mode, based on a
configurable system mode re-select time value from 0 to 480 minutes when zone temperature
demand is greater for cooling.
Supplemental heat shall be capable at the zone level during a system heating mode.
Zones requiring heat shall be capable of independent supplemental heating during a system
cooling mode through hot water valve, fan powered heat or auxiliary heat sources controlled by the
Zone Controller.
4. Economizer Operation:
On HVAC units equipped with economizers, integral economizer operation shall be initiated upon
a call for first stage cooling from a Monitor so configured. Economizer operation shall be
substituted for first stage mechanical cooling when outside air temperature or enthalpy control
conditions are suitable. On HVAC units not equipped with internal economizer control, the Monitor
shall interface with the Carrier Comfort Controller to provide full economizer control utilizing
outside air temperature and/or enthalpy control.
5. Bypass Operation:
The bypass system shall operate to maintain an operator configurable system static pressure
setpoint by modulating a bypass system damper. The bypass damper shall also be repositioned
automatically to maintain the required changeover modes and cycles.
B. Unoccupied Mode:
1. Fan Operation:
If the fan mode is configured to “ON” or “AUTO” the system fan will be brought on with first stage
cooling or heating when the VVT Comfort System is in the unoccupied mode. The system fan will
be released when the system demand has been satisfied.
A. Cooling Operation Staging Control
B. Heating Operation Staging Control
C. Economizer with Integral Control
All control of HVAC equipment will follow the same operation as in the occupied mode with the
exception of the VVT Comfort System controllers utilizing the unoccupied setpoints instead of
the occupied setpoints.