VALLOX 252 D
4
INSTRUCTIONS FOR USE
Pressure difference switch
LON converter
Ventilation control with voltage or current signals
• The fan speeds of VALLOX 252 D can be controlled with voltage or current signals
coming from the remote monitoring system.
• The signal can be used to select speeds 0...8. However, the maximum fan speed may not
be exceeded, if carbon dioxide or humidity control is active.
• The signal changes the basic fan speed.
• The signal does not lock the fan speed, i.e. it can be changed on the control panel within
the defined range. Carbon dioxide and humidity controls also operate within the defined
range.
Ventilation control with remote monitoring system
• With the help of an optional LON converter, VALLOX 252 D can be connected to a
remote monitoring system.
• Before connecting VALLOX 252 D to the remote monitoring system, make sure that they
are compatible.
• The remote monitoring system may be used to control the same functions that can be
controlled on the control panel.
• The remote monitoring system works in parallel with the control panel and the carbon
dioxide and humidity sensors.
Heat recovery bypass
• The aim of the heat recovery bypass function is to ensure that supply air coming to the
ventilation zone is as cool as possible. To do this, the heat recovery bypass function
compares the measurement data of the outdoor and extract air sensors.
• The heat recovery cell is bypassed when the post-heating function is off and outdoor air
temperature exceeds the setpoint.
• Heat recovery is active whenever outdoor temperature is two degrees below the setpoint.
• The setpoint may be changed within the range 0˚...+25˚C. (The factory setting is 10˚C.)
Heat recovery cell defrosting function
• The defrosting function prevents the heat recovery cell from freezing, thereby ensuring
that ventilation works in cold periods, too.
• The defrosting function uses preheating and, when needed, stops the supply air fan on
the basis of the measurement data received from the temperature sensor that detects the
temperature of exhaust air after the heat recovery cell. When the risk of freezing passes,
preheating will be switched off and the supply air fan will start automatically.
• The preheating activation temperature of the defrosting function (factory s3˚C),
the temperature for stopping the supply air fan (factory s1˚C) and the operating
temperature hysteresis (factory setting 1˚C) can be set on the control panel.
Defrosting of water circulated post-heating unit
• The defrosting function aims at preventing the water circulated post-heating unit from
freezing. The automatic function stops the supply and extract air fans of the ventilation
unit whenever outdoor temperature descends below 0˚C and supply air temperature
goes below +7˚C, in which case the control valve becomes wide open and the message
FREEZING ALERT shows in the control panel display. The function opens and closes the
points of the fault signalling relay at 10-second intervals.
• The fans start automatically as soon as supply air temperature exceeds 10˚C.
Filter guard function
• If VALLOX 252 D is equipped with a pressure difference switch for the supply and/or
extract air ductwork, the switch monitors the pressure difference in the whole ductwork.
When pressure has risen (e.g. because of a clogged filter), the filter guard indicator ( ) in
the main display of the control panel lights up.
• When the lamp is lit, the filter guard closes the points of the fault signalling relay.
