Patent ID: 8464783

Claim:
A method of optimizing a level of an antifreeze agent in a heat transfer fluid of a heat exchange system of a ventilation system, comprising the steps of: operating the heat exchange system of the ventilation system i) to deliver heat to incoming air by outgoing air heating the heat transfer fluid, and ii) for the heat transfer fluid to transfer the heat collected from the outgoing air to warm incoming air, the operating step including monitoring a temperature of the incoming air, wherein the level of the antifreeze agent in the heat transfer fluid is dependent on the temperature of the incoming air; monitoring a temperature of the heat transfer fluid; determining a wanted level of the antifreeze agent based on the monitored temperature of the incoming air; and controlling a current level of the antifreeze agent in the heat transfer fluid including i) adding further antifreeze agent to the heat transfer fluid when the current level is a predetermined amount lower than the wanted level, and ii) removing an amount of the antifreeze agent from the heat transfer fluid when the current level is a predetermined amount higher than the wanted level, wherein said determining step further comprises determining the wanted level of the antifreeze agent further based on long-term statistics over relations between the monitored incoming air temperature, previously chosen levels of the antifreeze agent associated with the monitored temperature of the incoming air, and a resulting temperature of the heat transfer fluid for a local installation, the long-term statistics being based on actual monitored incoming air temperature values and the monitored resulting temperature of the heat transfer fluid for the local installation in the operation of the heat exchange system of the ventilation system.