LX Series Unit Ventilator Controller User's Guide
37
Calculating the Space Temperature Setpoint
When nviApplicMode is set to HVAC Auto, the space temperature setpoint
determines whether the unit enters a cooling or heating state. Space temperature
setpoint calculations are addressed before state descriptions to ensure your
understanding of how the state is selected.
When you configure the Unit Ventilator Controller, you enter three pairs of
setpoints for the four operating states. Because bypass mode uses the same
setpoints as occupied mode, there are only three pairs. These setpoint pairs are
occupied, unoccupied, and standby. They are stored in SCPTSetPnts. SCPT is an
acronym for Standard Configuration-Property Types.
The UVC selects a pair of setpoints as the active setpoints depending on the
current mode. Then, the active setpoints are modified using the following
variables:
•
nviSetPoint
•
nviSetpointOffset
•
Setpoint Input
The Effect of nviSetPoint on the Active Setpoints
The variable nviSetPoint allows you to change the setpoint using FX Workbench.
If nviSetPoint has a valid value and if the mode is standby or occupied, then the
two active setpoints are calculated as follows:
The value of Setpoint_move and Setpoint Offset is added to each member of the
active setpoint pair. For the following example, the Setpoint Offset value is
considered to be zero.
Example:
If nviSetPoint is equal to 75°F (23.9°C) and the two setpoints are 72°F
(22.2°C) and 68°F (20°C), then:
The two setpoints become 77ºF (25ºC) and 73ºF (22.8°C).
Note:
The network variable nviSetPoint is inactive in unoccupied mode.
(
)
Setpoint_ move
=
−
+
nviSetPo
occupied cool
occupied heat
int
_
_
2
Offset
Setpoint
ove
Setpoint_m
oints
ActiveSetp
points
Active_Set
+
+
=
(
)
2
68
72
75
ove
Setpoint_m
F
F
°
+
−
°
=
F
°
=
5
ove
Setpoint_m
