Tall Homemade Cabinet Style Incubator Heat/Fan Question

[_Randall_]

Quote:
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

Quote:
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.

This thread is getting more interesting by the moment...... My cabinet bator (in the making) will be 20-1/2" x 22-1/2" x 31-1/2" inside............with 3" return gap at bottom of false back (was 7"). I was planning on putting two of these in the false back at the top: http://www.grainger.com/Grainger/ww...uery=4wt47&op=search&Ntt=4wt47&N=0&sst=subset , wired to individual switches. That's ~210 CFM with both running, ~105 with one running. Things to consider......... If I need both, then turn both on. If I only need one, then one is there idle if the one being used quits. NOW, considering theoretical air flow, if one runs, and the other one is idle, IF I don't block off the idle fan, then there's "a" path of least resistance for return air (instead of making the trip to the bottom, coming under the false back, and loop again, again, etc........ Can I block one off if not needed? Yeah, but it gets back to the question of, "Do I really need 2"? I'm installing the false back this weekend, and it's 1/8" aluminum sheet, and the decision will have to be made by then.

 

[SED]

Another question, would fan placement be an important factor in a good air flow. Should the fan be centered? Mounted on the left? Mounted on the right? If you have two fans side by side and one was off and the other was running, would that affect maximum air flow efficiency because the one running would be "offset" to the center? Does the heat source need to be behind the fan or in front of the fan? Blow up or down (assuming the heat is at the top). These questions may have already been answered so I will need to re-read the posts again. It looks like the Sportsmans and others blow from back to front and not really down at all. Is this correct? If I rebuild it I really want to get the best efficiency out of it and would like to be able to incubate around 200-300 eggs in it. Thanks for all the replies! This has been a great discussion so far!

 

[_Randall_]

I'm using the GQF Sportsman theory on mine........ water shelf with fan(s) "centered (horizontally) above it. MY theory about the orientation of the fan / heat / water is.........fan blowing across heating element ....... then across the water............... resulting in warm air blowing across the water creating moisture in the bator atmosphere. I don't want to "pull" heat across my fan(s)........that a direct heat load on them that's not welcomed. I want to "push" the air through the heating element, then across the water.

 

[aprophet]

does anyone know which way GQF blows/draws theirs does the fan blow towards the door or to the back I have fans draw heat aross them all the time I would be more concerned drawing moisture across them I live at the coast and change a lot of outdoor motors I suspect it has more to do wit the salt then the wet

 

[_Randall_]

Quote:
The one my buddy has blows air across the heating element.......then across the water towards the front. My theory is if you pull air across the water, and push it through the heating element, you're "drying the air back out" to some degree.

 

[SED]

My next question. I have the heating element pictured below. When I wired it up, it turned extremely hot and out of shape. Is there a specific way to wire these up that I may have missed?

 

[_Randall_]

Quote:
Questions: Did you stretch the coiled nichrome wire out straight to get it around the insulators? Have you cut and shortened the element? You do have a thermostat in the circuit, don't you?


Follow the concept of this schematic: http://www.gqfmfg.com/pdf/THERMOSTAT WIRING.pdf

 

[muddstopper]

Whew, thread getting so long I am starting to lose track.
Randall, the measurements you gave for your incubator , 20-1/2" x 22-1/2" x 31-1/2". is close to what mine is. Its 30" tall, x 18"wide and 22 deep. For your cabinet, I would just go with one fan. Read back to where SED took one fan out of his and suddenly it started maintaining more even heat. If you have to go back later and add a extra fan, it will be much easier than removing one and trying to plug the hole.

SED, I would place the fan in the middle. the air flow should leave the fan and then blow across the heat strip, then across the humidity tray, if you pull the hot air off the heater and then blow it thru the fan, the fan can overheat. I have actually melted the plastic out some of the cheaper fans. The air in the sportsman blows at the top, from back to front. air flow is directed downward thru a gap between the top shelf and the front door.

The pic you show of the heat strip is the same pic on Cutler Supply web site and is the same one I have ordered, but not the one currently in my incubator. If this strip overheated and sagged, there can only be one possible explaination. And that is, you didnot have the coil stretched properly. If this coil is stretched properly, you can plug it directly into a wall outlet and it will just get hot and not cause a short. you probably couldnt hold it in the outlet to really test this out, but that is the way it would work if you could hold it in the outlet.

The coil of wire is nichrome wire and works based on resistance to electric current flow. The resistant causeing the heat. The longer this wire, the more resistance it has and the less heat it can create. If any of the coils in the heat strip are touching, you have shortened the lenght or distance the electrical current has to travel thru. The shorter the distance, the less resistance and the more heat. No resistance would be a dead electrical short and would blow a fuse. You also dont want to stretch the coil into a straight line. Metal expands when it is heated, stretching the wire until it is straight will cause it to sag when its heated. Not to mention the coil of wire would be very long when stretched tight. Also, I hope you didnt cut this wire to make it fit your insulator placement. Shorting the wire means less resistance and more heat. If you have a Ohm meter, connect the leads to each end of the wire and start stretching it out and watch the resistance numbers start to rise. Fully compressed, it should read little to no resistance, When fully stretched, with no coils touching, it will probably read around 60-80 ohms of resistance. The thermostat has nothing to do with the coil getting to hot and sagging. The thermostat doesnot regulate electrical current, it only cuts it on or off as the case might be. The current flowing thru the thermostat is the same current and amps being pulled out of your wall outlet.

 

[_Randall_]

Quote:
I think SED is wondering if he has the right "wires" hooked up to it (right SED?). If so, you hook the black "hot" wire to one end of the element, and the common "white" to the other. At this point, the thermostat "closing" makes the circuit hot. When it "opens" (based on where you have the setting), the "electricity" stops flowing through the element, thus letting it cool.

 

[muddstopper]

You only have 2 wires, one hot and one neutral. It doesnt make any difference which end is hooked where, it will work either way. You could leave the thermostat out completely and the heater coil shouldnt turn red and sag. If the coil is over heating, the coil cant be properly stretched resulting in coils touching each other. The coils touching is what is causeing the overheating, not which end he has what wire hooked to. Either that or his voltage is out of wack coming from his wall outlet.