icubator temp probe

[Malum Argenteum]

I was going to mention that if there's a situation in which there's a possibility of a problematic temp gradient in the incubator, then a fan should be part of the design. I see he added a fan in the second video. He commented that two fans made the incubator too hot (because of the motors' energy use), and that's because he's using fans that are too large (too much airflow) and too inefficient. That just needs a little circulation, not be a wind tunnel. One or two 120mm computer fans would be sufficient in there, and have the further benefit of being adjustable if they're too strong.

Since it seems his overheating problem was caused by radiant heat, putting the heat element behind a panel such that air can flow over the heat element but so that radiant heat isn't such a factor in heating the eggs is an effective solution. This radiant heating issue is a real problem with Hovabator-type incubators, and in any application where radiant or contact heat is used where what is really needed is convective heat. So there are some basic design flaws shown in those videos which can be addressed pretty simply and effectively.

But anyway, there's a more basic reason not to put the probe on the heat tape. Suppose we want the incubator to run at 80F, and suppose that when the heat tape is at 90F then the air is 80F (choose whatever numbers seem realistic; the point is that the heat tape temp is always going to have to be higher than the target air temp, and that we're thermostatically setting the heat tape temp). So we put our probe on the tape and set it for 90F, and the air temp stabilizes at 80F.

This arrangement will be less than ideal in two very common situations. One happens when the door gets opened. Usually this causes the air in the incubator to cool off (unless the room is exactly the temp we're targeting in the incubator; in this case we don't actually need an incubator), and then when we shut the door it heats back up until it reaches the target temp. If the tape is set at 90F, the incubator will regain its target temp much less slowly than if the heat tape could get hotter until the air reaches the target temp. Whether this is a big problem depends on how long is acceptable for eggs to be out of the target temp range. I assume, though, that returning to target temp faster is better than slower.

Another more serious issue is when the heat loss from the incubator changes because the temp in the room has changed, which can happen because the incubator is in a home (where fluctuations are typical) or because the room HVAC fails, or someone messes with the room thermostat, or leaves a window open overnight, or whatever. When the heat loss from the incubator changes, then the 90F heat tape will not keep the air in the box at 80F. But if the probe is measuring the air temp in the incubator, then the air temp in the incubator will maintain at the set temp.