The Priva Compass can operate many different types of cooling This article explains some of the more common cooling methods available.
Roof ventilation
The most common form of cooling in a greenhouse is the use of roof vents. As cooling is needed, the vents will start to open. Typically the lee vent (the vent that is not facing the wind) starts to open first and if there is not enough cooling, the wind vent (the vent that is facing the wind) starts to open. Greenhouses could also have a single roof vent that can either be a wind or lee vent depending on where the wind is coming from.
Roof and side ventilation
Greenhouses sometimes use combinations of roof vents and side vents. During the cold periods of the year, the roof vents are the only vents used for cooling. As the outside temperature warms up, the side vents are also used for cooling to ensure a maximum air exchange.
Exhaust fans
Greenhouses can also be cooled by exhaust fans. Typically the exhaust fans are mounted on one side of the greenhouse and there is a louver or an air inlet on the other side of the greenhouse. The exhaust fans are controlled by the Priva Compass as cooling stages and there is a separate control in the Priva Compass for the air inlet. When one of the cooling stages are needed, the air inlet will open up first before the cooling stage is activated.
Exhaust fans with modulating side vent
Instead of an air inlet, sometimes a side vent is used to act as an air inlet. The side vent can modulate to control the amount of air entering the greenhouse.
Exhaust fans with pad wall
A pad wall is often used together with exhaust fans for cooling. The pad wall is kept wet when the exhaust fans are running. As the air is drawn through the pad wall, evaporative cooling occurs, lowering the temperature of the air being drawn into the greenhouse. The pad wall is operated as a cooling stage.
Roof vents with exhaust fans and pad wall
It is also possible to have a combination of roof vents together with exhaust fans and a pad wall. The roof vents operate as a first mode of cooling and if the conditions are such that the roof vent is no longer able to cool, the Priva Compass switches over to a second mode of cooling. The roof vents close and a combination of exhaust fans and a pad wall are used for cooling.
Cold water cooling systems
The Priva Compass can also control the mixing valves as a method of cooling. In this case the mixing valve will open to allow cold water from a chiller to enter the system to lower the temperature in the greenhouse.
