Lennox PCUS User Manual page 12

3.4 ANTIFREEZE OPERATION
The anti-freeze protection function is intended to prevent the formation of ice on the water coil (if the unit is
equipped with a water coil).
The function is activated when the contact opens on a digital input suitably configured by manufacturer parameters.
If digital input 2 is used, set L1.3 = 2 and L1.4 = 1, if digital input 3 is used, L1.5 = 2 and L1.6 = 1 must be set.When the
protection intervenes, the fans are turned off, the air inlet / outlet shutters closed and the water valve is activated,
whether it is on / off or modulating (if heating mode is selected).
3.5 AIR INLET / OUTLET DAMPER OPERATION
The PCUS control is able to operate air inlet / outlet dampers equipped with on / off servocontrol.When the unit is
switched on, the shutter opening signal is activated and after a settable waiting time the fans are switched on.The
waiting time can be set by user parameter U0.7 in an admissible range between 0 and 180 seconds.
3.6 FREE HEATING / COOLING LOGIC OPERATION
The operating logic provides for the activation of an on / off type output for the activation of the recovery bypass.
The activation of this output occurs when the external air conditions allowit.If the outside air temperature is higher
than the desired set and the room temperature is lower than the desired set, the free heating function is activated.
If the outside air temperature is lower than the desired set and the ambient temperature is higher than the desired
set, the free cooling function is activated.
To avoid oscillations of the bypass there is a differential defined by parameter U0.2 which by default is set at + 1 ° C.
3.7 DIRTY FILTER INLET SIGNAL
The PCUS control has an on / off type input for the dirty filter signal. The preset input is DI1 and by default the dirty
filters function is activated when the input contact is closed.
The manufacturer parameter L1.1 equal to 1 activates the dirty filters function, while the parameter L1.2 allows to
invert the logic of the signal.
L1.2 equal to 0 causes the dirty filters signal to be activated when the contact is closed, L1.2 par to 1 causes the
signal to be activated when the contact is opened.
The activation of the dirty filters function activates the signal given by the 4th icon, however by default it does not
perform any action allowing normal operation of the fans, if instead you want the dirty filters functionality to stop
the ventilation, the manufacturer parameter must be set to 1 L0.2.
3.8 REMOTE ON/OFF SIGNAL
Remote switching on / off of the unit with the help of an external switch is possible using the DI2 input by setting the
manufacturer parameter L1.3 = 1, while the manufacturer parameter L1.4 inverts the contact logic.With L1.4 = 0 the
ignition of the unit occurs with closed contact, while with L1.4 = 1 the ignition occurs with open contact.If remote on
/ off is selected, it overrides the on / off button on the display, ie if the unit is turned off from the display it turns
on again immediately, and vice versa if it is turned on it turns off immediately.
3.9 EXTERNAL ALARM INPUT
The external alarm function is possible with the aid of a digital input (DI3), which allows the immediate stop of the
ventilation.Use only a clean contact for this function, which can be activated by setting the manufacturer parameter
L1.5 = 3.
3.10 ALARM OR UNIT SIGNAL OUTPUT ON
It is possible to use a digital voltage output (230V ac) to interface with external devices for two possible functions
of alarm present or unit on. For example, to use output DO1 as an alarm present, the manufacturer parameter L2.1 =
4 must be set and L2.2 allows the logic to be inverted, with L2.2 = 0 the output will be active if there are no alarms
and will be disabled if there are alarms while with L2.1 =
1 the output will be active if there are alarms and deactivate with no alarms.
If the DO1 output is already intended for another use, the same functionality is possible with one of the other outputs
on the controller.Again as an example, in order to use the DO1 output as an On unit, parameter L2.1 = 3 must be set
and L2.2 allows you to invert the operating logic as specified for the example above.
3.11 NOTE ON MANUFACTURER PARAMETERS
The manufacturer parameters allow to modify the functionality of all the inputs and outputs of the device and if
not correctly set they can compromise the regular operation of the unit, for this reason it is absolutely necessary
to avoid their modification other than what is not expressly reported here.
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