Trane VAV VV550 LonTalk, Installation & Operation Manual

Page: 74 / 116

74 VAV-SVP01A-EN
Sequence of Operations
Fan Off Delay
There is a 15-second fan OFF delay. When reheat is turned OFF, the controller turns the fan OFF 15
seconds later.
Ventilation Flow Control
Ventilation flow control (VFC) is one of three supported control algorithms. It is applied to a VAV
terminal and used to temper cold outdoor air (OA) that is brought into a building for ventilation
purposes. The tempered air is intended to supply an air-handling unit (AHU), which provides
comfort control to the zones it is serving. The VAV terminal supplies the correct amount of
ventilation air and, when possible, tempers the ventilation air to reduce the load on the air handler.
See
Table 13, p. 74 for ventilation flow control output control.
The ventilation flow control process is a constant volume, variable temperature process.
Single duct VAV units with either electric or hot water reheat are used. Fan-powered units are not
used for ventilation flow control.
Ventilation flow control must have an auxiliary temperature sensor that is located and configured
as a discharge air temperature (DAT) sensor. The required range of discharge air temperature
setpoints is 45°F to 70°F (7.22°C to 21.11°C).
Ventilation flow control staged reheat control (electric or hot water) achieves a 30-minute average
discharge air temperature to within ±5°F (±2.78°C) of the discharge air temperature setpoint when
the inlet temperature is within the control range. Ventilation flow control modulating reheat control
(hot water only) achieves a discharge air temperature to within ±5°F (±2.78°C) of the discharge air
temperature setpoint when the inlet temperature is within the control range.
Air Valve Control
Ventilation flow control uses the air valve as a constant volume device. The unit is given a constant
flow setpoint for air valve control (configured ventilation setpoint); the air valve only repositions
itself in response to changes in inlet static pressure. By using pressure independent control for
ventilation purposes, a constant volume of fresh air can be maintained, regardless of small
fluctuations in inlet static pressure. Ventilation flow control unit can use a Ventilation Setpoint from
a BAS system if it is valid. If unit is stand alone the ventilation flow control uses one of the following
two airflow setpoints:
• If no reheat being used, it uses the configured Ventilation Setup Occupied Setpoint;
• If reheat being used, it uses the configured Local Heat Minimum Airflow.
Table 13. Ventilation flow control outputs
Occupancy mode Source temperature Air valve control Reheat control
Occupy standby
bypass
Any
Constant volume (if valid,
communicated ventilation
setpoint; if not valid,
configured ventilation
setpoint)
Electric VFC staged reheat control
Staged hot water VFC staged reheat control
Modulating hot water
VFC modulating reheat
control (same as STC
capacity control)
Unoccupied
Communicated source temperature (if
valid; if not valid, discharge air
temperature) greater than configured
OA low limit
Closed, 0%
Electric Off
Staged hot water Off
Modulating hot water Off
Communicated source temperature (if
valid; if not valid, discharge air
temperature) less than configured OA
low limit
Closed, 0%
Electric Off
Staged hot water
On, 100% freeze
protection
Modulating hot water
On, 100% freeze
protection