To keep the eggs in the incubator on the required egg shell temperature, the produced metabolic heat must be taken out of the machines. In the past, multi stage machines were often used, which cooled the eggs later in the incubation process by adding new eggs in the machines that required heat. In this way, the amount of cooling capacity per machine was limited. In modern single stage machines we need to cool much more, as all the eggs in the machine will produce a significant amount of heat towards the end of the incubation period.
In principle, there are three different ways to cool the eggs:
Cooling by air exchange: replacing warm air for colder air will remove heat from the machines
Cooling by evaporation: evaporation of water costs energy, so humidifying the air will have a cooling effect
Cooling by cooling coils: cold water in cooling coils will be warmed up and therefore have a coolig effect
The downside of the first two methods is that it interfers with the settings and the ventilation of the machines. The downside of the last method is that it is a relative expensive system which requires large amounts of cold water, especially in single stage machines that require a lot of cooing.
In modern machines we see that the cooling capacity through cooling coils has been increased compared to the past. This is because the climate control through cooling coils is not only more precise but especially more uniform, as bringing in cold air and cooling through evaporation tends to give more local cold spots.
Many older (single stage) machines do not have enough cooling capacity through their cooling coils to be able to take out the embryonic heat sufficiently without having to increase the ventilation or humidification. Although general rules cannot be given as there is huge variation in machine types, some basic principles can be checked.
Decreasing the temperature of the cooling water is an option, but this will result in more condensation in the machines, as the cooling coils will be below the dewpoint.
It is often possible to split the cooling coils into smaller sections, each with its own inlet and outlet. If a section is split up in two smaller sections, the temperature difference between inlet and outlet will be half of the original value, and the average temperature of the cooling water will be much lower, as well as more evenly distributed.
Air flow will bring the heat from the eggs to the cooling coils, so an attempt should be made to get the air flow over the eggs as high as possible, for instance by putting the eggs in a horizontal position in the last days of incubation. This is not helpful or possible in every machine, but can sometimes help to cool the eggs better and make the egg shell temperature more evenly distributed.