Fan continuously on (or off during heating)

[ericatdallas]

So I built my wife a forced-air incubator. I originally built it so that the fan was continuous but the fan kept blowing on the heating element and it actually raised the temperature after the heater turned off. I then set it so that the fan turned off when the heating element turned off.

The heating element is a 100W PTC heater attached to a large aluminum heat sink with fins. The fan is a 120mm computer fan.

I calibrated the thermometers and the temps read 100F when level with the egg. The controller shuts off at 100F.

Is this okay?

My other option was adding a small 80mm fan that circulates the air continuously but located at the opposite side of the incubator.

Another consideration that I might play with is turning the main fan to a lower voltage (maybe 5V) continuously.

Anyone else have suggestions?

This is our second batch of eggs. The last batch on day 6 didn't have veining EXCEPT for one with some red veins. My wife opened them up after not seeing anything when candling them. We were also thinking maybe they were improperly stored or too old (some of them sat for 7 days). We also thought it might be the temperature because we set it at 99F.

We tried a second batch of eggs 12 eggs with the oldest being 24 hours and the youngest being a couple of minutes. She candled them today and said she didn't see any development. She's going to wait until day 10 before making the call. These were set at 100F.

Now my thinking is that maybe the eggs are experiencing wild temperature fluctuations due to the fact that the air isn't being continuously circulated. In this situation, maybe we should set the temperature for 102F at the top of the eggs?

Any thoughts?

 

[Egghead_Jr]

Fan should run continuously. Both table top incubators I've owned get hotter after the element turns off. It's natural as the element still has heat. The opposite is true for the coldest temp in the incubator will be 30 seconds or so after the heating element turns on. The element is not heated yet so incubator is still cooling. Just the way of things. If the temp swing is too much to your liking then add heat sinks. Water bottles or stones or what have you that will stabilize the heat more. The thing to remember is the eggs themselves will be stable temperature even though the air temp in incubator swings back a forth a few degrees. The mass of the egg retains the average temp of what the air is doing. The more eggs and heat sinks in incubator the less the air temp swing is. But does a large swing really matter? Not so much. The egg is stable.

 

[ericatdallas]

Okay, thanks. I'll keep the fan moving continuously before the next batch. Maybe there's a chance this batch is still salvageable.

Currently though, even it looks like the incubator is pretty consistent across the volume. I have three thermometers (calibrated w/ ice water bath) that all agree with each other. Which is why I wasn't too concerned about the fan until now.

Heck, it may not be any of those. These are new laying hens and roosters so it may just be a fertility issue. We're trying to control the humidity, but that's another potential factor.

However, until I find out what's really causing it, I'm going to try to control as many variables as I can until I get some hatches.

 

[Egghead_Jr]

Definitely wait until day 10 to candle. With poor light intensity or not candling in pitch dark you wont see much in an egg. I use to candle day 7 for years and stopped two years ago as it only showed me some were developing but couldn't make any kind of call on what to toss unless it was completely clear. Day 10 is a user friendly day to candle for sure.

As for humidity- unless you live in a arid area or heat with wood you may not even need to add moisture to the first 18 days. I like a bit over 30% RH for that time. If running dry I get 25-28%. Many people run dry for first 18 days. In table top size I add a double shot glass. I can fit it to side of auto turner. That little bit of surface area of water gets me over 30% RH which is my preference. Day 18-19 up the humidity to 70-75% RH.

That's my recommendation anyway.

If there is no development at all in eggs on day 10 candle then you've a fertility issue. Have you cracked an egg to see if it's fertile? Not one in incubator but one from birds you have in fridge or counter. Crack it open and look for a dot in yolk. Here is a good post on it here at BYC:

https://www.backyardchickens.com/t/16008/how-to-tell-a-fertile-vs-infertile-egg-pictures