Heat placement in incubator

[GoodOldDays]

Hi all.

Building an incubator out of a little bar fridge over here.

I've done my research on R.H. and the pros and cons between still air and forced draught.

I'm going with the still air option but I have hit a bufuddling concept and cannot seem to find research on the matter, so I am asking you wonderful people for your opinions.

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In a still air incubator the norm is for the heat source to be above the eggs. This makes sense because in nature the heat comes from above too.

What I find befuddling about this is that in a still air incubator there is a significant temperature difference between the upper and lower sides of the egg.

Why not put the heat source below the eggs?

If the heat is below the eggs, the heater itself warms the lower side and the fact that warm air rises means that the difference in temp across the egg would not be so drastic. (In theory)

Also if you were to put the heat below the egg with a vent near the heat source, and a vent at the top of the incubator, the hot air rising would draw in fresh air and expel old 'used' air at the top after it has passed over the eggs much more effectively.

I feel that light bulbs used as the heat sources may need a small shield above them to distribute the heat more evenly, so that the eggs directly above the light do not get too hot. But this is easy to achieve.

I understand that the lights/shields may get dirty once the chicks start hatching. Do you think that they would get dirty enough in that short period of time to cause such a problem that the heat source needed to be above? Is that the only reason people put the lights/heat above?

Any insight would be appreciated. I just don't understand why it is common practice to put the heat source above.

Thank you.

 

[ChickenCanoe]

I don't recommend still air for an incubator that tall. The air thermally stratifies more than you realize. Still air are usually those Styrofoam incubators that are barely taller than a rack of eggs. Even in those little things the temperature can vary as much as 2 or 3 degrees from the top of the egg to the bottom.

It is possible people put the heat above because a hen heats from above.

Rather than light bulbs, I find metallic heat elements to be more reliable. An incandescent lamp will cycle on and off many times during an incubation, thereby shortening its life. You don't want it to burn out in the middle of development.

I probably didn't answer all your questions but that's just my 2 cents worth.

 

[GoodOldDays]

The fridge will be on it's side. The internal space will be 42cm from bottom to top. Is that still too tall?

I'm still undecided on the heat source but I think I probably will end up with light bulbs just because it's so cheap and easy but it will be dual bulb so chances of both of them blowing before I fix it are pretty slim.

Thanks for your advice. You got me a bit worried about the temp gradient now but I think it' worth a shot, I can always add a fan if all else fails

 

[ChickenCanoe]

IMO it is still too tall. Give it a try and plan your electric for adding a fan later.
Set it up and take temps at all levels - that will be your sign.
I have a fairly tall incubator with lots of fans but it is still over 1 degree F between racks. I'm about to make a fix for that.

 

[pasuit]

I don't recommend still air for an incubator that tall. The air thermally stratifies more than you realize. Still air are usually those Styrofoam incubators that are barely taller than a rack of eggs. Even in those little things the temperature can vary as much as 2 or 3 degrees from the top of the egg to the bottom.

It is possible people put the heat above because a hen heats from above.

Rather than light bulbs, I find metallic heat elements to be more reliable. An incandescent lamp will cycle on and off many times during an incubation, thereby shortening its life. You don't want it to burn out in the middle of development.

I probably didn't answer all your questions but that's just my 2 cents worth.

Excellent2

 

[pasuit]

Excellent2 cents. I agree

 

[Laodicia]

Hi all.

Building an incubator out of a little bar fridge over here.

I've done my research on R.H. and the pros and cons between still air and forced draught.

I'm going with the still air option but I have hit a bufuddling concept and cannot seem to find research on the matter, so I am asking you wonderful people for your opinions.

--------------------------
In a still air incubator the norm is for the heat source to be above the eggs. This makes sense because in nature the heat comes from above too.

What I find befuddling about this is that in a still air incubator there is a significant temperature difference between the upper and lower sides of the egg.

Why not put the heat source below the eggs?

If the heat is below the eggs, the heater itself warms the lower side and the fact that warm air rises means that the difference in temp across the egg would not be so drastic. (In theory)

Also if you were to put the heat below the egg with a vent near the heat source, and a vent at the top of the incubator, the hot air rising would draw in fresh air and expel old 'used' air at the top after it has passed over the eggs much more effectively.

I feel that light bulbs used as the heat sources may need a small shield above them to distribute the heat more evenly, so that the eggs directly above the light do not get too hot. But this is easy to achieve.

I understand that the lights/shields may get dirty once the chicks start hatching. Do you think that they would get dirty enough in that short period of time to cause such a problem that the heat source needed to be above? Is that the only reason people put the lights/heat above?

Any insight would be appreciated. I just don't understand why it is common practice to put the heat source above.

Thank you.

I think part of the reason to put the heat above is that the embryo floats and it is whaat needs the correct temp. My main reason for putting my heat where i did (On a back wall with a heat sheild - hardware cloth to block access with tinfoil tied to it. - and 2 smaller bulbs directly above the eggs ) was because i didnt want my electrical sitting in water for lockdown.

 

[GoodOldDays]

I think part of the reason to put the heat above is that the embryo floats and it is whaat needs the correct temp. My main reason for putting my heat where i did (On a back wall with a heat sheild - hardware cloth to block access with tinfoil tied to it. - and 2 smaller bulbs directly above the eggs ) was because i didnt want my electrical sitting in water for lockdown.

Hmm that is a good point. You're talking about the condensation dripping down to the bottom yeah?
Would the condensation not be dripping off the top to though? I guess it has to be on a wall to avoid getting water on the bulb itself.

What if I put the light bulbs on either wall but still under the eggs? With some kind of bracket to bring them in closer to the middle a bit. That should work well.

What I've read on still air incubators is the 'mean' egg temp (where you want the correct temp) is the halfway point on the egg. I also read that for some reason eggs in still air incubators are more tolerant of fluctuations than eggs in a forced draught incubator but they cant explain why.

www.brinsea.com/Articles/Advice/WhyFan.aspx

 

[lazy gardener]

Good point about the humidity. I think that's a very good reason to stay with the standard of heat source above. I've been hatching in home made incubators for 4 years, using light bulbs (2) x 40W as my heat source, and have never had a bulb blow. I hatch 1 - 2 broods/year. My last build was a cooler. I had a fan, but simply couldn't get the temp regulated. Even after playing with adding and blocking vents, tin foil baffles... I fudged with that thing for hours. Finally, out of desperation, I unplugged the fan. The temp leveled out and I ended up with a great hatch. BTW, don't forget: forced air temp = 99.5* (I use 100*) and still air = 102*.

 

[Laodicia]

Hmm that is a good point. You're talking about the condensation dripping down to the bottom yeah?
Would the condensation not be dripping off the top to though? I guess it has to be on a wall to avoid getting water on the bulb itself.

What if I put the light bulbs on either wall but still under the eggs? With some kind of bracket to bring them in closer to the middle a bit. That should work well.

What I've read on still air incubators is the 'mean' egg temp (where you want the correct temp) is the halfway point on the egg. I also read that for some reason eggs in still air incubators are more tolerant of fluctuations than eggs in a forced draught incubator but they cant explain why.

www.brinsea.com/Articles/Advice/WhyFan.aspx

hmm, I've had a really hard time getting humidity to stay up for my lock down. it might not be too bad in a fridge type of setup. my current HM incubator is a .75" plywood box that has silicone painted on the floor so it wont leak and insulation board sitting on top of that in an attempt to stop loosing so much moisture. the last batch i did the insulation board was sitting in about an inch of water just to get the humidity up. (I was fine for humidity without fans but not temperature) I think the hardest part will be getting a consistent temp with still air. my only experience with a still air from start to finish was not pleasant. i was constantly adjusting the location of the eggs up, down, back, closer, etc. though at the time i didn't have a dimmer or thermostat. I did manage to hatch 3 eggs that time, but i didn't really sleep for 3 weeks.

I think the best advise would be try out what your planning without eggs for a couple of days get the temp to stay consistent or at the very least mark your hot and cold spots. and then see what happens when you add water as a trial lockdown. I could never get my temp to go back to normal in my mock lockdowns without fans. but the fans kill your humidity... it's a balancing act and the only way you'll know for sure is to give it a shot.