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Minimum Venting and Purging
Purging is the process of evacuating stale contaminated air and replacing it with fresh outside air. Any combination of
fans and inlets can be set up to purge.
Minimum ventilation is the process of bringing outside air into a building even when the indoor temperature and
humidity do not require it. This helps keep ammonia, dust and carbon dioxide from accumulating. When outside
temperatures are cold, minimum ventilation may be necessary even though you are also heating the building.
You will see one of two menus depending on how the building is set up:
• Building Purge Setting menu - If no fans, or only stir fans are installed, the controller assumes you are running a
simple
natural-ventilated building
and displays the Building Purge Setting menu.
• Minimum Ventilation and Purge Settings menu - If fans (other than stir fans) are installed, then the controller
assumes you are running a
power-ventilated building
and displays the Minimum Ventilation and Purge Settings
menu.
The humidity-related menu items shown below appear only when at least one humidity sensor is
installed. If more than one Humidity sensor is installed, the average reading of all sensors is used to
determine if the purge should be performed.
If you are running a natural-ventilated building,
the Building Purge Setting menu is displayed.
A purge cycle can be triggered by the Purge Delay timer or by the Humidity Delay timer. The purge cycle runs for the
time specified by either the Purge Time ON or the Humidity Purge ON depending on which delay timer triggered the
purge cycle. The two possible purge conditions are:
• All curtains and ridge vents have been fully closed for the duration specified by the Purge Delay timer. Air inlets
are not considered to be curtains when checking for all curtain devices closed. Or,
• All curtains and ridge vents have been fully closed and the humidity level has been continuously at or above the
Humidity Purge Setpoint for the duration specified by the Humidity Delay timer.
Normally the Humidity Delay timer would be set for less time than the Purge Delay timer so that under high
humidity conditions a purge cycle would take place more frequently. The default Humidity Setpoint of 100% disables
the humidity purge.
When a purge occurs in a natural-ventilated building, the curtains and inlets open to the Purge
Opening Size that you entered for each device group.
Building Purge Setting Menu
Introduction
Natural Ventilation
Conditions for Purging