Ideal arrangement of the fans:
Both fans on suction side
In this arrangement the correct pressure difference of outdoor air to outgoing air is generally available. By installation of a throttle flap in the outgoing air duct ahead of the rotorsystem it is possible to regulate the pressure difference if necessary.
Outgoing air fan, suction side
Outdoor air fan, pressure side
There is no risk of air transfer from outgoing air to the outdoor air. Too great of a pressure difference should be avoided so that not too great amounts of air are fed through the purge sector and thereby unnecessarily increasing the feed volumes of the fan. In case of high system pressures additional support fans are needed.
Both fans on pressure side
This fan arrangement should only be selected when the mixing in of recirculating air is without importance. It is difficult to achieve the proper pressure difference for the function of the double purge sector.
Outgoing air fan, pressure side
Outdoor air fan, suction side
This fan arrangement may be used only in systems in which recirculating air operation is permitted for the operational conditions.