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As you know I use many LGs in local classrooms. These are still air with turner. (Yes, I am a true believer in LGs) It seems one of the bators just wouldn't work right this year, so I added a computer fan to it. At first I put it in so the air was blowing down on the eggs. This worked, but for some strange reason the eggs in the center, below the fan, stayed cooler than I wanted them. So I turned the fan upside down and added half inch spacers, so the air is forced up and flows evenly over the eggs. Ran for five days, until power outage, and held at 99 to 99.5 degrees. Today, after 4 days the power came back on and the temp is back to 99 degrees and holding. We are going to put this bator in a classroom over the Christmas holiday and see what happens. The classroom temp will be set at 65 degrees, so there should be no problem there. We are going to set up a temp recorder that will give us a reading of the temp over the time period. This test will be made on 3 bators, 1 still air, 1 with a fan down and the test model, fan up. On Jan. 10th, we will see what happens. 36 eggs in each, which one will have the best hatch? Anyone want to guess? I wish this test could be made without the children coming back. That way the only time the door would be opened is on day 18 to turn the turners off and kick up the humidity. Hey jamie, sound in. Need your thoughts on this.

 

[Mahonri]

I'm guessing fan up...

... guess we'll see!

 

[muddstopper]

I am just going to throw this out there and see what flys back.
Fans are meant to circulate the air inside the incubator. You only need a certain amount of movement to push the air around and this should create even heating. Now, throw in a big fan that is moveing bunches of air and you would think this might be better, but not necessarly true. Air speed can do many things, one if the air is moveing to fast across the egg surface, it can create and evaporative effect, pulling moisture from the inside the egg. This would probably raise the humidity levels inside your incubator, but actually lower the humidity inside the eggshell. Not good for hatches. Fans also create a positive air pressure inside the incubator, provided that the fan has someplace to draw fresh air from. To much airpressure will cause air seepage from around the incubator lid. This air seepage will allow some of the heated air, as well as your moisture, to escape. This would make temp and humidity control a lot more difficult. If the air being drawnback in because of the suction caused by the fan, (thru the fresh air vent), is lower in humidity than the air inside the incubator, you will have a harder time trying to maintain humidity levels.

Still air incubators rely on convection to move the hot air around inside the incubator, considering that most still air heatstrips are located in the top of the incubator lid, and heat rises, the only heat realized at the bottom of the incubator tray is a result of raditation. Meaning the top side of the egg is going to be much hotter than the bottom side. When you stop to think about this, that is exactly how a hen would set a egg, her body heat radiating down thru the egg. Brisnea makes a big deal about heating eggs in a similar method with their $4000 Rolex incubators, but their incubators dont reach heats of 130*+ and are continuously turning the eggs while applying heat. A hens body temperature isnt 130* either.

I'll stop here and see what others have to say on this subject.

 

[rebelcowboysnb]

I don't think up or down is the issue. Its the vent right over the fan that is. Move the fan or or plug the vent. Fan blowing down would be drawing cold air in that vent an putting it on those close eggs. Fan blowing up would push hot air out the vent. Because the cold air replacing it would be coming in all the other vents you would not see a cold spot. The issue both setups have is that you are speeding up the air exchange rate so it also speeds up evaporation rate. Air exchange rate has as much or more to do with evaporation than humidity. http://cmfarm.us/ventilation.html
Move the fan or plug that vent.

 

[muddstopper]

Rebel, I read you link. I agree with most of what you siad. Here is where I disagree.

Air exchange is necessary, so moveing the fan or just plugging the hole is not going to fix the problem entirely. Air exchange is necessary because of a build up of CO2 gas insde the incubator as the eggs are developing. Live eggs and even rotten eggs will exchange gasses because of the microbiology involved in the growing, or rotting phases of the egg. further, the microbiology gives off all kinds of other gasses, such as methane, sulfur dioxide and, well you get the point. Anyways, this old atmosphere that is created inside the incubator cabinet needs to be exchanged for good O2 gas to enable the eggs to develope properly. Simply plugging up the vent holes might allow humidity levels to rise, but it also locks up the deadly gasses inside the incubator. This is where some middle ground has to be reached between proper air exchange and loss of humidity due to outside atmosphere conditions.

Moving the fan away from the vent holes will only allow as much air to be exchanged as could be caused by air pressure of the fan. Since the fan wouldnt be able to pull in much air, it also couldnt push out much air and a neutral pressure situation would occur. Move the fan to far away from the vents and all air exchange might stop completely. Placeing the fan directly infront of a vent port would cause a massive increase in air exchange and positive incubator air pressure. This would mean a rapid air exchange and a loss of heat and humidity. Still this would still be the best place to locate the fan, but only if certain conditions are met. To reduce the rate of air exhange, and the resulting heat and humdity loss, one simply needs to restrict the size of the vent to the point that the inside of the incubator cabinet maintains a positive air pressure of not more than 0.2"

A good friend sent me these instruction on how to build a U-manometer for measureing air pressure, below are his comments pertaining to incubators and air pressures and I have attached his drawing for building your own easy as pie to build U-manometer.

There is no need for high air pressure inside the box. If you allow more fresh air to enter than the amount you are bleeding it will be fine. Constructing air pressure meter is very easy:

Use transparent water hose of 6 to 10mm diameter and fix part of it U-shaped (1ft length) on a piece of wood. Fill the hose with water partly and use some chemical stuff (or coffee ) for colour to see the water level easily. Put one end of the hose into the box and leave the other end open (ambient air). The water will be displaced on the opposite side of the "U" indicating positive pressure.

I made a sketch illustrating the function of an U-manometer. Don't use an inch-scale but use fragments of an inch for a scale. A pressure of 0.2" is more than sufficient, and should be decreased to a maximum of 0.1" (equivalent water height ~2.5mm). At a pressure of 1" the door will pop open when unlocked. (I doubt the fan will have that high pressure)​

 

[rebelcowboysnb]

Unless you are in a extremely high altitude the minimum air exchange needed to change the bad air for good is achieved by the thermal lift because the 100 degree air in the incubator in a room of something like 70 degrees. Only one top vent is enough to do it.(LG) It comes factory with it plugged. If you add a fan nowhere near the vents you lower the air pressure very slightly in the incubator but it really does not change the air exchange rate, Its still the same because it still has the same thermal lift. Adding more ventilation using a fan at a vent means more than needed an more evaporation than needed.

 

[Junkmanme]

I added a computer fan to a Little Giant incubator. I also used "spacers" to provide room for air-flow. Then I made a "baffle" from a tin/steel coffee-can lid (for the purpose of keeping the air from blowing directly upon the eggs. I won't be using it to incubate until shortly before Spring, 2010, I expect. (Just getting things ready for that time.)

I expect that this "Rube Goldberg" set-up should work just fine. Any comments?

Here is a picture:

-Junkmanme-

 

[muddstopper]

Rebel, I have never fooled with a LG or any of the other styrofoam incubators, so I am a little lost as to how many or where the vent holes are placed. It seems to me you are suggesting that there is only one vent hole placed in the top of the lid. Assumeing that this is correct, when the top of the incubator is closed the only place for air exchange would be the one tiny vent hole. Now if this is so, the heat inside the incubator would produce some positive pressure which would be vented thru that one hole, but where is the air exchange going to take place. Of course, if you are opening the incubator to candle or turn the eggs, then yea, you will be getting plenty of air exchange, but you are also loseing all your heat and humidity. For the thermal lift you are suggesting to take place, the incubator has to has some provision for the cool air to move downward to replace the hot air that is riseing, the hot air cant excape thru one hole without creating a vaccum to draw in replacemment cool air. For what you are suggesting to work, there would need to be another vent hole somewhere in the bottom of the incubator, or enought seepage around the lid to allow cool air to enter the incubator. Without taking a close look at the LG incubators I cant say one way or the other.

Now this is just my opinion based on not ever haveing fooled with, or even closely looked at, a stryrofoam type incubator. I would have at least two vent holes in the incubator for air exchange. I would place the fan directly over, or very near to, one vent hole and allow air pressure to excape thru the other vent hole. The ventholes would be restricted in size so that there would always be a positive pressure (0.1-0.2 inches on the Umanometer) inside the incubator and the fan speed regulated so as to not produce more than 9ft per minute of wind speed. This should ensure that to much air wasnt exchanged and that heat and humidity could be maintained and allow for good air movement inside the incubator. In such a small incubator as the stryofoam type, this would mean a very small or slow moving fan, and also very small vent holes. All you really want to do with the fan is create air movement, not a wind. One could also use more than one vent to exhaust the air pressure as long as the holes where reduced in size to maintain the correct positive pressure inside the incubator. I have read where some people use a toothpick to punch additional holes and would think this size vent hole might make a good starting point.

Everybody will just have to draw their own conclusions to what I have just said. If I run across a LG bator for cheap, I might buy it just to test my theories and see (IF) what I suggested could be true. Until then, I will defer to those that actually own and use the styrofoam incubators.

Bill

 

[spydertoys]

My question...how are you going to keep the humidity where it should be if you aren't adding water for all that time?

 

[rebelcowboysnb]

muddstopper
That may be where the misunderstanding is. The LG has the whole bottom filled with holes the size of a #2 pencil lead. In the top there is 2 holes about the size of the hole in the middle of a CD. It comes with at lest one plugged. The LG will incubate just fine in most environments with one of the top vents plugged. Many people open both to make sure they have enough air exchange. That probably doubles the exchange rate an evaporation rate but is still with in reason that you can adjust humidity to get the evaporation rate you want. If you add a fan under an open top vent, no matter if it is blowing down or up you ether create positive or negative pressure ventilation. Ether of which is overkill. To much ventilation will make the incubator use more electricity, cause cold spots an may even make the incubator fail to maintain temp. An again it multiplys the evaporation rate of the eggs. So in my opinion the fan should be somewhere other than under the top vent or that top vent needs to be plugged.