32 VAV-SVX07F-EN
UC400 Controller Points and Parameters
Flow Setpoints Setup
• Airflow Setpoint Minimum: Although the UCM will read flow down to 5% of cataloged, the
range of MIN FLOW settings is 0% or 10% to 100% of cataloged. The UCM will not drive its flow
below this minimum flow value under normal operating conditions while in the cool mode.
Cool mode occurs when cool air is in the supply duct. The entry in this field must be less than
or equal to the entry in the Airflow Setpoint Maximum field.
• Airflow Setpoint Maximum
: This
range is 10% to 100% of the cataloged unit CFM size.
Cooling and heating flow can be edited to zero.The UCM will not drive its flow above this
maximum flow value under normal operating conditions while in the Cool mode. Cool mode
occurs when cool air is in the supply duct. The entry in this field must be greater than or equal
to the entry in any of the Minimum fields.
• Standby M
inimum Airflow: Occupied standby mode is used to reduce the heating and
cooling demands during the occupied hours when the space is temporarily unoccupied. For
example, it can be activated for a classroom currently not in use. Standby Minimum is the
minimum amount of airflow desired during this mode.
• Airflow Setp
oint Minimum Standby Heat: Occupied standby mode is used
to reduce the
heating and cooling demands during the occupied hours when the space is temporarily
unoccupied. For example, it can be activated for a classroom currently not in use. Airflow
Setpoint Minimum Standby Heating is the minimum amount of airflow desired when in the
heat mode during this mode.
• Airflow Setpoint Minim
um Heat: T
he UCM will not drive its position/flow below this value
under normal operating conditions while in the HEAT mode (warm air in the supply duct) or
while it is using local heat.
• Airflow Setpoint Maximu
m Heat: The controller ente
rs maximum flow heat on receipt of
a communicated command and remains in Airflow Setpoint Maximum Heat until the command
changes. The controller maintains the flow rate at the heating maximum airflow. This is
normally used with a rooftop unit with staged heat that needs a Max constant volume of air
movement to keep the heat exchanger from overheating and tripping the heat in the rooftop
unit tripping on a high limit safety.
• Airflow Setpoint Minim
um Lo
cal Heat: If the Min Local Heat flow is enabled, then this
Minimum Local Heat setpoint is used to determine the minimum position/flow instead of the
Airflow Setpoint Minimum Heat when local heat is on. This entry must be less than or equal to
the entry for Airflow Setpoint Maximum Heat.
Discharge Air Reset Limits:
The following parameters are used for Single Duct Units that are equipped with either modulating
hot water reheat or SCR electric heat, which allows variable airflow when reheat is activated (for
example, “dual maximums” control sequence).
• Airflow Setpoint Reset Mi
nimum Local Heat: Th
e minimum position/flow when local heat
(either modulating hot water or SCR electric) is on. This entry must be less than or equal to the
entry for Airflow Setpoint Reset Maximum Local Heat. When reheat is initially activated the air
valve opens to, and remains at, this minimum position/flow setpoint, while reheat capacity is
modulated to maintain the space temperature at the active heating setpoint. Once reheat
capacity has increased to the point that the discharge air temperature reaches the Discharge Air
Temperature Design Setpoint, the controller will begin to increase airflow above this minimum
setpoint.
• Airflow Setpoint Reset Maximu
m Local Heat: The maximum position/flow when local
heat (either modulating hot water or SCR electric) is on. This entry must be greater than or equal
to the entry for Airflow Setpoint Reset Minimum Local Heat. Once reheat capacity has increased
to the point that the discharge air temperature has reached the Discharge Air Temperature
Design Setpoint, the controller will begin to increase airflow above Airflow Setpoint Reset
Minimum Local Heat. If the air valve reaches this maximum setpoint, reheat capacity is allowed
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