LX Series Unit Ventilator Controller User's Guide38
The Effect of a Setpoint Offset on the Active Setpoints
Setpoint offset is added to the pair of currently active setpoints. For example, if the
setpoints are 72°F (22.2°C) and 68°F (20°C) and the setpoint offset is 2F° (1.1C°),
then the value of the setpoints with the offset are (72+2)°F (22.2°C+1.1°C) and
(68+2)°F (20°C+1.1°C).
The two possible sources of a setpoint offset are the network variable
nviSetpointOffset or a hardware input. nviSetpointOffset allows you to change the
value of the setpoint offset.
Hardware inputs are secondary to network variable nviSetpointOffset. For the
hardware input to be active, the value of nviSetpointOffset must be invalid and
occupancy mode cannot be unoccupied. The invalid value for nviSetPointOffset is
621.806°F (327.670°C). The input can be connected to a 10k ohm potentiometer in
the conditioned space.
Ventilation
This section discusses the processes that control ventilation only. Included is a
description of the processes that control fresh air intake and that may be active
when cooling processes, such as free cooling, are inactive. For an overview of
these ventilation processes, see Figure 15.
Ventilation Separate from Free Cooling
Free cooling uses cool outside air to remove heat from the building. Free cooling is
only an option and may be disabled in the configuration wizard. Even if enabled,
free cooling is always inactive when there is no cooling demand.
In contrast, there is a continuous demand for ventilation during occupied periods
and, depending upon your configuration of the system, there may be minimum
ventilation during unoccupied periods.
For example, during a heating state, ventilation occurs but free cooling does not.
This means that the damper is moved to a position that meets the demands for fresh
air without allowing more air to enter than is necessary.
Free cooling is part of the cooling state and is described further in the Free Cooling
section.
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