Tall Homemade Cabinet Style Incubator Heat/Fan Question

[muddstopper]

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I dont know rebel, I think I am going to agree to disagree and let it go at that. I think the air blowing down will cause the hot air to be at the bottom and then rise using convection to heat the upper part of the cabinet. Where as the hot air blowing in at the bottom is already being forced to the top which would make the bottom colder. Actually one should be able to get it to work either way so I say go with what ever a person feels comfortable with. My cabinet blows air into the tray area all along both sides from top to bottom, front to back. Air returns thru the bottom and up thru the false back. I dont know how I can compare it to a cabinet that just blows air down from the top or up thru the bottom.

 

[muddstopper]

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Ok, we know you are having humidity problems and temperature problems and your design isnt working. Having said that, please dont take what I am about to say as negative comment. I think you need to start over. What kind of cabinet are your trying to make your bator out of. Is it some sort of cooler, fridge, or a box you have built. Take a look at how the gqf incubator, that some one posted earlier in this thread, is assembled . For all of my and Rebels discussions, we both like to tinker and have different ideals of how we want something to work. On the other hand, everybody knows that the qgf sportsman incubators do work and work very well. Heres a few facts to consider.

1. In the Sportsman bator, there is only one fan and heat source.
2. The fan and heat source are mounted in the top of the bator blowing air across a pail of water and then down into the egg tray area.
3. If it was better to place the heater, water tray or fan somewhere else in the incbator, I am sure GQF would have figured it out by now.
4. Dickey incubators are a carbon copy of the GQF which is actually a copy of other brands. If relocating any of the working parts would produce better results, again I think one of the major manufacturers would have figured it out long ago.
5. If it aint broke, dont fix it. Meaning sometimes we make things more complicated than they need to be.

6. My personal incubator design is completely different than the gqf and the other manufacturers designs in the way I move the air around inside my cabinet. My design is going to be different than anything you are trying to build. Just because I say I like something to work one way, doesnt mean its going to work for you or anybody else unless they are trying to copy my design. If someone wants to copy my design, thats alright to, as long as they are not a manufactoring company who'es intentions would be to make money off something I have worked hard on and spend much money on getting it to work.

Post some dimensions of your cabinet, you may already have, but I dont want to look for them. A pic would be nice if you can take one. Also list what materials you have to work with and I will try to help all I can. I am sure a few others will throw in their 2ents worth as well.

 

[rebelcowboysnb]

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That I can agree to. Anything we say is speculation anyway without having that incubator in hand to test the fan both ways.
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SED... The only thing I see with the last drawing is the egg right over the light may be hotter. Other than that it should work fine. Shouldn't even need the top fan.... I keep coming back to thinking its to much ventilation. The humidity should be threw the roof with that much water an the temp should be even with that much air flow. To much cold outside air coming in is all I can think of that would cause low humidity an cold spots....

 

[_Randall_]

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Why would you reverse it? Heat is trying to go up. Its easier to force it down on the small side than it would be if you were trying to get it to go down on the big side.

My way of thinking, and feel free to correct me if you think I am wrong, is this. Forceing the air from the bottom up in the tray area will create a hot spot at the top of the tray area. Like you said, warm air will rise. In fact, blowing the air upwards will cause warm air pockets any place near the top of the tray area that there isnt an opening. A incubator cabinet and air flow isnt like it is in a house with a ceiling fan. In a house, you would want to move the air upwards to cause the warm air that gathers at the top of the room to move back down along the wall towards the floor, only to rise again, thus keeping the room temp more stable. In a incubator, its a little different in that the air you are moving around isnt staying in the same room, instead it is being pushed or pulled out of the room (tray area) to be reheated and then moved back into the room, (tray area). The moving air is always being effected by the variation in temperature between the outside of the cabinet walls and the warm air inside the cabinet. As the air moves along the walls, it is being cooled down. I dont want air that has already been cooled down to touch my eggs first. Instead I would much rather have the air right after it has been heated by my heating element to enter my egg tray area. This air is much easier to regulate the temperature of and will result in a more stable temperature inside the cabinet, than trying to regulate the air that is being cooled at varying degrees due to outside enviromental conditions. ex., air conditioner kicks on, someone opens a door or window to the room, someone decides to cut down the thermostat settings on the entire house. etc.I think everybody needs to stop thinking of forceing the air and instead think of just moving the air. You dont need massive air movement to control temps in an incubator. A gentle constant movement is all that is needed to mix the cold air off the side of the incubator cabinet, and the warm air being generated by the heat strip and fan.

This is Physics 101 at it's best as it relates to incubator temp and humidity! Very well put!

 

[SED]

I unplugged the top fan and guess what, the temps became more uniform. I thought for sure that the more air movement in the incubator, the more the temps would be uniform. Again, I think that I was putting too much thought into it. My current cabinet dimensions are (inside dimensions) 15"x15"x32" tall. Made out of 3/4" plywood with a clear plexiglass door with a 3/4" wood frame.

 

[_Randall_]

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Do you know what the CFM rating is on the fan you're using?

 

[SED]

Not sure of the CFM. I can look tonight when I get home. It is a 6" small desk fan so it circulates the air pretty good.

 

[aprophet]

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If you move the air too quickly past the heat source this can give you problems this is why the blower on an A/C gas pack has several speeds they slow down the fan when it goes into heating most who look at an cabinet bator do not realize it is just like a duct system on and A/C . I built a bunch of humidifiers for a rest home for a coupla years had to retrofit them to the A/C"s they had installed

 

[_Randall_]

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If you move the air too quickly past the heat source this can give you problems this is why the blower on an A/C gas pack has several speeds they slow down the fan when it goes into heating most who look at an cabinet bator do not realize it is just like a duct system on and A/C . I built a bunch of humidifiers for a rest home for a coupla years had to retrofit them to the A/C"s they had installed

Did some googlin', and found that one model of the GQF cabinet bators has a 400 CFM fan in it!!!! That's a bunch of movin' air!! http://dblrsupply.pinnaclecart.com/products/GQF_Hi_Volume_Fan_Motor_Bracket-558-159.html

 

[muddstopper]

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If you move the air too quickly past the heat source this can give you problems this is why the blower on an A/C gas pack has several speeds they slow down the fan when it goes into heating most who look at an cabinet bator do not realize it is just like a duct system on and A/C . I built a bunch of humidifiers for a rest home for a coupla years had to retrofit them to the A/C"s they had installed

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Randall, That 400cfm fan, is it in one of their 292 egg capacity incubators?. The bigger the incubator, the bigger the fan would need to be, but My incubator only holds three 48egg trays and I am using a 60cfm fan. I guess the question is, Is a 400cfm fan necessary because of design considerations, or could a person get by with a much smaller fan. Would my incubator benefit from adding a bigger fan as well. Here is what I do know, I started out with a 198cfm fan and kept downsizing the fan until I achieved even heating thruout the incubator cabinet. Maybe i could have achieved even heating by raising the fan size as well. Wait a minute, my cabinet is insulated and theirs isnt, maybe thats it.