VSC OPERATION AND MAINTENANCE INSTRUCTIONS 4 118 0324 2 IOM
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Topvex FC
Compact Air Handling Unit
Operation and Maintenance Instructions
Document in original language
125918-EN_GB
2015-03-16 A001
Operation and Maintenance Instructions
Systemair AB
4.4 Free cooling description
is function is used during the warm period to save energy by using cold outdoor air, e.g. during night
time, to cool down the building.
Note:
The following is only valid if the free cooling function is set to Acve in the program menu.
Free cooling is only activated when the following starting conditions are met.
Starting conditions:
• Less than 4 days have passed since the unit was last in running mode
• The outdoor temperature during the previous running period exceeded a set limit (+22°C)
• It is between 00:00 and 07:00:00 in the day (settable)
• The timer outputs for normal speed, Extended running normal and External stop are O
• A time channel will be On sometime during the recently started 24 hours.
The unit checks the night temperature (indoor and outdoor temperature) during 3 minutes at the set starting hour
when the fans are started so that the sensors can perform a temperature measurement. If above conditions are met
the free cooling function is started, if not the unit goes back to OFF position.
If the outdoor sensor is not located in the outdoor air inlet duct and a room sensor has been selected, the unit will not
start free cooling as long as all the temperatures are not within the start and stop temperature intervals.
Stop conditions:
• Outdoor temp above the set max value (+18°C) or below the set min value (condensation risk, +10°C)
• The room temp/extract air temp is below the set stop value (+18°C)
• One of the timer outputs for normal speed, External stop or Extended running normal is On
• The time has past 07:00:00.
If any stop conditions is fullled after three minutes, the unit will stop again. Otherwise, operation will
continue until a stop condition is fullled.
When free cooling is active, the fans run at normal speed or the set value for pressure/ow control and the digital out-
put Free cooling is active. The outputs Y1-Heang, Y2-Heat exchanger and Y3-Cooling are shut down. After free cooling has
been activated, the heating output is blocked for 60 minutes (congurable time). When using free cooling, an oset to
normal fan control setpoint is adjustable.