LX Series Unit Ventilator Controller User's Guide
46
Note:
The nviHotWater variable has priority for the water temperature either
from the input sensor or nviWaterTemp.
Heating Demand
Heating demand results from any one of the following:
•
an error between the active heating setpoint and space temperature
•
nviSlave
If heating demand is taken from nviSlave, then the Unit Ventilator Controller is
operating in slave mode and is receiving the heating demand from another unit.
Heating Output Sequence
Heating outputs 1–4 are staged outputs. Heating output 1 is the first heating stage
in the stage sequence. See the
section for more information.
Heating outputs 1–4 and Heating_Mod do not turn ON until all heating valve
outputs are at 100%.
Cooling Outputs Used to Heat
You can use cooling outputs 1–4 to heat if another output is configured as a
reversing valve. The reversing valve turns ON at the same moment as the first
stage of cooling.
If the cooling outputs are used to heat, then heating outputs 1–4 and Heating_Mod
do not turn on until the cooling outputs are at 100%.
Ending the Heating State
The heating state ends when there is no demand for heating, and the first heating
stage (if any) has operated for more than the minimum heating period.
If the PID loop control has accumulated bias during the heating stage, heating
outputs may not shut off when the space temperature reaches the setpoint. The
output shuts off when the bias reaches zero.
Night Purge
Night purge is used to freshen the building air before occupation or to cool down a
building before morning occupation. Night purge is a scheduled operation that
does not use any setpoints. During night purge, only free cooling is enabled. The
damper and fan respond to the cooling demand; heating and cooling outputs are
OFF.
The Unit Ventilator Controller enters night purge if nviApplicMode is set to
HVAC_NIGHT_PURGE. This can be the result of binding with a supervisory
Heating, Ventilating, and Air Conditioning (HVAC) device, an HMI, or a
scheduling system.
If frost protection is enabled, the heat turns ON if the temperature in the
conditioned space reaches 42.8°F (6°C) and turns OFF at 46.4°F (8°C).