Dynamics
Incubator Dynamics
by Greg Stephens
The three major incubator dynamics that need to be balanced are air flow, heat, and humidity. Designing an incubator that balances these dynamics is simple and can be easily done by anyone with the tools and basic knowledge of how to make these three dynamics work together.
Air Flow
Air flow, while not necessarily the most important dynamic, is certainly the force of balance for both the heat and humidity inside the incubator. Air flow will eliminate the gradients and heavy condensation commonly found in still air incubators while keeping your humidity at optimum levels. The fan used to create the air movement has to be sized, placed, and directed correctly.
I have found that the easiest way to properly size a fan for any incubator is the CFM rating. I personally prefer to have an air turnover rate of five to eight times the incubator’s total air volume per minute. In my experience a fan above or below this range will not balance the incubator dynamics as well as a fan in the five to eight times range. Placement will depend on the internal design and heat source placement. In my designs I like to utilize a section or enclosed area for the heat source. I position the fan as high in the main chamber as possible so it is blowing into the area containing the heat source moving the warmer and now heated air to the bottom of the incubator. This directed air flow will work with the normal convection air current and balance the overall temperature of the main chamber.
Heat
Heating an incubator is possibly the easiest part of the process.
While picking a heat source and thermostat may be the hardest.
I prefer to use flexwatt as a heat source because it is consistent, has a high amount of surface area, and is easily obtained. It is also easy to install and work with.
As for thermostats my new favorite thermostat for incubators is the Herpstat ND. It has some outstanding features such as power matching and sensor matching. These features allow the user to tune the power curve applied to the heaters to create stability and consistency. The sensor match feature allows you to adjust the sensor reading to match a trusted and accurate secondary thermometer like a laboratory grade mercury thermometer. Another good thermostat is the Helix basic but they have become hard to come by and pretty expensive when compared to the Herpstat ND. They also lack all the Herpstat features.
As I said I like to enclose the heat source so that the flow of air can be controlled and directed to flow across the surface of the heat source. I have not found a good formula for the total wattage to use as a heat source and just tend to make good use of the area I set aside for the heat source inside the incubator. In my opinion as long as you are using an insulated cooler or cabinet that has the right amount of air flow you will accomplish what you set out to do.
The wattage of the heat source will be far less important. Thermostat probe placement is dependent on which incubation method you prefer though in my opinion keeping your thermostat probe in the main flow of air at around egg box height works the best for all methods and creates the most consistent and stable environment.
Humidity
So with all that said the last dynamic to balance is humidity. The easiest way to add humidity into the incubator is standing water, whether it is in a container or in the bottom of the incubator itself. Again in my experience the placement and the amount of surface area of the water are more important than just having water in the incubator.
I prefer to set up the water so that it is the 1st thing the air exiting the heat source of the incubator contacts. This loads the heated air with water vapor and helps keep the heated air from drying out the egg boxes and eggs. This set up also helps stabilize the air temperature after the unit is opened and any heat is lost. While the heat source is warming, the water will heat the incubator’s air as the air passes across the waters surface. Once the heat source is hot, the water will then moderate or cool the incubator’s air through evaporation.
Now there is one last thing in regards to humidity. With a high volume of air flow and saturated air comes condensation. We all know that differences in surface temperature cause condensation in wet air environments. The use of the insulated cabinets or coolers helps with the majority of condensation issues inside the incubator. The only place the majority of incubators seem to still have condensation issues is the glass/acrylic top or door used to make observations without dumping the heat inside the incubator. These surfaces are typically not exposed to the same temperatures on both sides which results in a cooler surface than inside air and LOTS of condensation. The amount of condensation depends on the temperature difference between the inside of the incubator and the room it is used in.
The eggs boxes themselves may end up having condensation issues. Condensation issues on large surface areas of the incubator such as the door or top and egg boxes can lead to less than optimal humidity levels and egg dehydration issues by stripping the water vapor from the air and potentially the eggs themselves. These problems are easily eliminated by heating the air above the acrylic top on cooler incubators. With cabinet style incubators an insulated outer door or insulated and heated outer door will do the trick.
Once these three dynamics are balanced the incubator will be stable, consistent, and functional.