Controlling the humidity in an incubator using an ultrasonic fogger

Controlling the humidity in an incubator just got easier.

If you have been following along, you know I have done quite a few modifications to my Little Giant incubator to increase the hatch rate. A few tweaks here, a temperature controller there, a humidity controller, etc. I was using the WH8040 humidity controller to simply monitor the humidity to tell me when I needed to add water to the reservoirs in the incubator. It also showed me how much the humidity was raised during the hatch when I placed wet cloths inside. But I decided that if the humidity controller can actually switch something on to increase the humidity, why not give it a try? So instead of constantly fighting to keep water in the reservoirs, I will be controlling the humidity in an incubator automatically.

Please note that this modification may not work with a still air incubator very well. The forced air incubators draw air into it and forces the air out the ventilation holes. A still air does not move air at all so the fog has no real way of being drawn from the jar into the incubator itself. If you do decide to give it a try with a still air, let me know how it works.

Wiring it all together:

I wired an extension cord end to the controller as shown in the following picture so I could just plug the fogger in. I used an extension cord end I had hanging around, you can use a similar end or even wire up an actual outlet and box if needed.  My cord end had a white, black, and green wire. I just cut the green one back out of the way because there is nowhere to connect it on the humidity controller anyway. The fogger I recommend and use is only 24 volts, not the 110 volts that powers the humidity controller, so it cannot be hardwired to the controller.

Ultrasonic fogger to raise the humidity in an incubator

Wire the WH-8040 humidity controller to your incubator using the following wiring diagram:

Wiring the fogger to raise the humidity in an incubator

You may find it impossible to actually put two wires under the screws on the controller. Simply cut the wire from the male plug, strip the wires back, and wirenut the new wires that will go to the fogger. Black wire to black wire, white to white. Remember to only do this when everything is unplugged!

Once the cord end was wired I started to modify a mason jar lid to work with the ultrasonic fogger that I used. The fogger creates a fine fog that gets transferred to the incubator via a tube. This fog raises the humidity very quickly. I used a quart jar and recommend that size so you don’t have to fill it too often. After 3 days of maintaining the set humidity, the level of the water has gone down less than 1/2″. The reason is because the water is being turned to a fog. The fog raises the humidity quickly. You can see the fog in the jar in the previous picture.

I simply drilled 3 holes in the lid of a canning jar as shown in the picture. One for the cord, one for the tubing, and one to allow air into the jar. Then, I used 1/2″ clear plastic tubing to allow enough air to flow through it. Originally I had used smaller tubing but found I had to close the vent hole in the top of the incubator to allow the fan to draw the fog through the tube into the incubator. because that vent is closed I had to allow fresh air in somehow. That is the reason for the third hole in the jar lid; to allow fresh air into the incubator when needed. I used a step drill to drill the holes.

Once the jar is complete, make a hole in the side of the incubator for the tubing. The location of the hole should not be too near the humidity sensor. I placed mine in the opposite corner. Just be sure the end of the tube is not going to let the water spray directly on an egg.

I filled the jar halfway with water and set the controller to turn on and off at the desired humidity. Why halfway? Because the fogger cannot have too much water over it or it doesn’t work well at making the fog. How did I come up with the desired humidity? Well, everything I can find gives me a wet bulb humidity, I have a dry bulb. I have found no cross reference that gives me a good setting to use. So I am faking it by using the humidity the incubator typically runs. For me, that is 25% or so. During hatch, the incubator runs about 40%, so that is what I will use. I programmed the controller accordingly.

The great part of using a mason jar is they are easily accessible and you can clearly see the water level to know when to add some. I made a mark on the jar when I discovered exactly where the level above the fogger works best to make it even easier. I use a large turkey baster to add water through the large hole in the cover.

The following picture shows the temperature controller and the humidity controller readouts. I simply zip tied the humidity controller to the temperature controller for easy viewing. In reality, both can be remotely mounted as long as the wires are long enough.

WH8040 humidity controller

And of course, programming the controller is vital, so here is how it is done:
  Press and hold the SET key for 3 seconds to enter the setting mode.  The first value is HC, which tells the unit whether to dehumidify, or humidify.  Press the SET key again, and use the up or down arrows to set this value to H (humidify).  Then press the SET key again to save the value and return to SET mode.  Press the UP key to move to the next value, D, which is “Hysteresis.”  Leave this at its default setting.  Next, press the UP key again to move to the next value, LS, which is the lowest humidity range you want to keep.  Press the SET button and adjust this setting to 25, or whatever the lowest humidity is acceptable for you.  Then press the SET button again.  Use the UP arrow to move to the next value, HS, which is the maximum humidity.  Click SET and use the arrows to set this limit to 40. The remaining settings can be left at their defaults unless you need to modify them later.  CA is humidity calibration…if your unit isn’t measuring the humidity correctly, you can override the settings by plus or minus 5%.  PT is the delay time between turning your humidifier on and off, and the default is set at 1 minute.  Press the RST key to leave the set mode.

Caution: During the first few weeks of incubation the humidity is lower than the last few days. The last few days the humidity needs to be higher for the chicks to not dry out. So your initial setting should be something like 25% for the low set point and maybe 27% for the high. During the last few days when the humidity should be higher those settings should be something like 35% for the low and 40% for the high.

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