Carrier TruVu VAVB3-E2 Installation And Startup Manual page 78

Start-up
Local air source modes – If the zone controller is stand-alone or if linkage communication fails, the zone controller
monitors the cfm (liters/second) for fan status and its SAT sensor to determine if the primary air source is
providing heating, cooling, or recirculating air in a fan-only or ventilation mode.
HEAT
VENT
COOL
OFF
TruVu™ VAVB3-E2
Installation and Start-up Guide
For Series or Parallel Fan controllers when the zone terminal fan is off or for single
duct controllers: The zone's local heat has not operated for at least 5 minutes, and
the SAT is more than 5 °F (2.8 °C) warmer than the space temperature. If the
terminal fan is on, the SAT must be more than 8 °F (4.4 °C) (warmer than the
space temperature.
In all cases, Heat mode is maintained until the SAT drops 2 °F (1.1 °C) below the
space temperature.
The zone's local heat has not operated for at least 5 minutes and the SAT is between
65°F (18.3°C) and 80°F (26.6°C).
The zone's local heat has not operated for at least 5 minutes, the current mode is not
Heat, and the SAT is less than 65°F (18.3°).
Terminal airflow is used determine if the primary air source fan is on or off. If the
terminal's Damper Position is greater than 95% and the cfm (liters/second) is less
than 10% of Nominal CFM* (liters/second) at 1" (.249 kpa) Velocity Pressure for 1
minute and the cfm (liters/second) Setpoint is not equal to 0, then the fan is
determined to be off. If cfm (liters/second) is greater than 20% of the Nominal CFM*
(liters/second) at 1" (.249 kpa) Velocity Pressure, or greater than 50% of cfm
(liters/second) Setpoint for 10 seconds (whichever is greater), then the fan is
determined to be on.
Occupied/Unoccupied Min CFM (liters/second) must be set for greater than 10% of
Max Cool cfm (liters/second).
* Shown on Properties page as Manufacturer's specified air flow at 1" water
column: for both English and Metric applications.
English: Use manufacturer's cfm at 1" water column
Metric: Use manufacturer's liters/second at .249 kpa
NOTE A local air source fan mode of OFF usually cannot be detected on series fan
boxes. This is because the terminal's series fan, when operating with the terminal
damper open, usually creates enough primary airflow to prevent the control from
properly detecting that the air source is off.
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