Poor hatch in incubator

I made an incubator out of an old mini fridge, programmable thermostat, and light bulb. There is a small pan of water for humidity. The eggs seem to start out fine, but about the last week everything dies in the shell. I have only had one chick hatch out of 3 tries with 2-4 dozen eggs at each try. There is a small vent hole to prevent overheating. I have hand turned the eggs 2-3 times a day with each run. What am i missing? I have had success with the little styrofoam incubators, so I know eggs are good, along with candling and seeing chicks forming. TIA for ideas/suggestions.

Only one vent hole? Also, are there multiple layers in the fridge of eggs? What was your temp and humidity?

Yes, one vent hole about size of quarter. Its what i found was about right size to keep the temp steady at 99. Im not opposed to adding more vent holes if that's the problem. There are 3 shelves for eggs. Not sure of the humidity, but the water pan is about 4 inches wide.

The vent holes are not made to prevent overheating. They are to provide oxygen to the eggs. If I am right, the egg that hatched was probably on the top. I would 100% suggest getting a hydrometer. You never know. It could also be as simple as that.

jadenthechicken said:

The vent holes are not made to prevent overheating. They are to provide oxygen to the eggs. If I am right, the egg that hatched was probably on the top. I would 100% suggest getting a hydrometer. You never know. It could also be as simple as that.

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xs 2. I would provide more venting for air circulation, and add a couple hygrometers. Did you do eggtopsies and what did you find when you did them? Wet chicks? Shrinkwrapped chicks? Do you check the air cells at all to know if the humidity is working for your eggs and the air cells are growing at the right rate?

I'd say if your temps are accurate, that's where I'd start trouble shooting. Air circulation and humidity.

FortitudineFarm said:

I made an incubator out of an old mini fridge, programmable thermostat, and light bulb. There is a small pan of water for humidity. The eggs seem to start out fine, but about the last week everything dies in the shell. I have only had one chick hatch out of 3 tries with 2-4 dozen eggs at each try. There is a small vent hole to prevent overheating. I have hand turned the eggs 2-3 times a day with each run. What am i missing? I have had success with the little styrofoam incubators, so I know eggs are good, along with candling and seeing chicks forming. TIA for ideas/suggestions.

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Got any pic's?
One vent hole will not allow air exchange.
location of the vent hole's is important.
Air circulation is important.
Willing to offer help if you can provide more info.

I had only candled at about day 8-10 to pull any in developing eggs. After that, I hadn't done any checking. I have since, googled some on air sac, but other tips are appreciated. The picture shows the basic set up. The eggs are o trays like egg cartons and sit on the shelves. Thermometer is just a second temp check as I thought that might be th problem. How big should I make vent hole? How many?

FortitudineFarm said:

I had only candled at about day 8-10 to pull any in developing eggs. After that, I hadn't done any checking. I have since, googled some on air sac, but other tips are appreciated. The picture shows the basic set up. The eggs are o trays like egg cartons and sit on the shelves. Thermometer is just a second temp check as I thought that might be th problem. How big should I make vent hole? How many?

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Vent hole location/size is according to how your incubator is built. I do not see a fan---without a fan how do you control hot spots. Its got to be alot hotter in the area of the light bulb than on the top shelf say.

Building a incubator is more than heat and a thermostat in a cabinet. You have to do what it takes to make the temp as even as you can through out. Vents has to be installed to allow fresh air so it does not run out of oxygen or become stagnated. Hot air rises so with your set-up you would need a vent hole on the bottom close to the bulb and at the top so as the heat of the bulb rises it draws air in from the bottom and escapes out the top. If you will study a few of the best working incubators you will see about everyone of them has the heat source at the top and the heat is blowed to the lower part. Take the cheap Styrofoam----still air----the heat is in the lid/top but it is in a entire circle from the round heating element instead of in one spot like a light bulb.

If I was going to build in this fridge like you are using----I would put the bulb's at the top---maybe mounted on the sides---I would use 2 bulbs(one on each side) with 1/2 the wattage of the one you got. 1/2 the wattage will keep from having a hot spot like with one bulb twice as hot. I would mount 2 fans behind the bulbs--a few inches from the back----blowing on the bulbs blowing towards the front. Behind both fans on the back I would drill 1/2" hole through the back then in the bottom back--a few inches off the floor I would drill 2 more 1/2" holes through the back. So when the fans are running they will be circulating the air inside as well as drawing a little air from the outside and air will vent back through the bottom holes----giving you some fresh air, I personally would add a top shelf a little below the bulbs to put my water container on and this will allow the fans to blow through the shelf towards the front to create a better air flow. Look at a GQF cabinet pic to see better what I am saying with the top shelf and 2 fans. Any Questions---just ask.

@PD-Riverman thank you for the suggestions. I will work on modifications as you've suggested. any recommendations for fans?

FortitudineFarm said:

@PD-Riverman thank you for the suggestions. I will work on modifications as you've suggested. any recommendations for fans?

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I would use computer fans, but big enough that they move good air movement----air movement is important to keep a more even temp throughout. With your fridge---probably 2--3 1/2" computer fans. Most computer fans are DC voltage, but finding a 12 vdc power pack to run them is usually as simple as looking in your junk box/yardsales/Radio Shack!

See the pic of mine under my name----I built both of those---mainly from things I had laying around----the one on the right has 2 12vdc computer fans running off one of those power packs(similar to cell phone charger)---That's my hatcher---it hatched 233 chicks out of 236 eggs 3 weeks ago--last hatch. The one on the left has 2 fans the same size as the hatcher but they run on 120 volts ac---again using what I had laying around.