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AK1000
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Registered: 06/06/16
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5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or?
#27302332 - 05/10/21 01:57 AM (3 years, 8 months ago) |
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- I got this sheet pan cabinet recently and I'm in the process of making it a dehydrator and I'd like some advice.
- I used a hole saw to drill holes on the bottom to act as an air intake for the heat source with a fan placed at the bottom. It's stainless steel all around and insulated all around. It has doors on the front and back.
- I used mesh window screens that are adjustable and they fit perfectly.
- Space heater fail: Tried a forced-fan space heater on the bottom with a fan that could be pointed straight up but it would overheat and turn off after a few hours. (It was nicely bringing temps up to 120-130F inside but not able to push air through all the mush and mesh all the way to the top anyway.)
- Now I am trying a different setup that's much more efficient but I have some questions. I got 4 ceramic heat bulbs (like the ones for reptiles, set in clamp lights) placed on the at the bottom (they are 150watts each 600watts instead of 1500watts space heater) and there's also a fan at the bottom. The bulbs are hooked up to a thermostat placed outside that will shut off if the room goes over 85F for now (this will be dialed in more).
Funny Heat bulb photo example:
- Fun facts on the mega surface area: Normally, large (non-commercial) dehydrators have 10 trays that are 13x15" (195in²) so about 1000in². This one is 18x31" (558in²) and could take 12 trays, so about 6696in², so about 7x the capacity, so I could easily load up enough to yield 4+lbs of dried mushrooms. Will report later on true capacity on the next flush. (I got 40 monotubs going.)
Questions: Should I set the fan on the highest speed to ensure it goes all throughout? Or will that distribute the air too fast? Is it better to set the fan speed lower? Should I set a fan inside somewhere else as well? Or maybe put a fan near the top on the inside top pointing UP to help it pass through more? Top panel was loosened to allow venting so that can easily be done. If no fan needed on the top, how much venting/air gaps should I allow for the top panel? Better to vent it more or less?
I'm also curious about the efficiencies of the horizontal airflow dehydrators with the back-mounted fans versus vertical ones. I know back mounted fans are more efficient (dont need to rotate trays), but I may lose a chunk of real estate doing that most likely. Maybe I can one day put the heat bulbs evenly distributed in the back with multiple smaller fans in between or in front of them? Thoughts?
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Hindsight
Mad Scientist


Registered: 01/24/21
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: AK1000]
#27302357 - 05/10/21 02:26 AM (3 years, 8 months ago) |
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I built a dehydrator similar to that some years ago for food drying. The problem is that it’s going to be super hard to answer the questions you are asking because it’s all one big experiment and one trial after the next to get everything dialed in just right from temp to airflow to venting to distribution and evenness. I can tell you’ve already considered and thought through all the variables you have to play around with. On mine, I used light bulbs as well, but just plain incandescent ones (200 watts each). I let the natural rise of the heat handle distribution. I found that I had to build some adjustability into my top vents in order to control the heat, and it was also very sensitive to ambient air temps - as in, you’d think a 10 degree rise in ambient temp would cause a 10 degree rise inside the dehydrator but nope! Was more like 30 degree rise. Eventually I just broke down and bought a nice dehydrator (Excalibur) and it’s been nice not having to fuss with it (the DIY experiment was fun for a while), however, at the size you’re dealing with, I’m not sure you have many other options.
If I had that cabinet that you do, I’d get a small electric ceramic heater (the kind with a fan in them and cost about $35 and can be bought nearly anywhere called “personal space heater”), and I’d attach it to the outside of the cabinet at the back bottom facing horizontal, with a hole cut in the cabinet the same size as the output area of the heater. I’d set the heater thermostat to max and I’d plug it into a temp controller with the temp probe inside your cabinet. I would not dry anything directly in front of the heater so you’ll lose a little cabinet space from that but that’s no big deal. I wouldn’t add a fan to force air out of the cabinet - the heater fan will serve as the air pump, but you might benefit from putting a computer fan or two inside to just move air around a bit if you find you have really bad circulation. I’d have just a couple 2” holes on the top for exhaust and you can always add more if needed or else add foil tape to partially cover them if they are too much.
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AK1000
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: Hindsight]
#27302364 - 05/10/21 02:34 AM (3 years, 8 months ago) |
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Hey thanks for the feedback!
I can't do the space heater setup below, on the outside of it because there's a really thick metal "brace" welded in an X position crossing the whole bottom (it's like 3" thick) and there's no way I have the tools to cut a hole into metal that thick (and it would lose structural integrity). It sounds like I should maybe add some small cpu/muffin fans somewhere else (prolly back mounted) toward the top half to circulate heat around better there.
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Hindsight
Mad Scientist


Registered: 01/24/21
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Last seen: 1 year, 8 months
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: AK1000]
#27302970 - 05/10/21 12:30 PM (3 years, 8 months ago) |
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No I was trying to say you'd leave the floor/bottom intact, and instead cut into the back of the cabinet opposite the front door, and you'd do it at the very bottom of that back wall. It would blow air into the cabinet from the lower back wall and blow it toward the front door and it would then circulate up and around from there. This is how it works in an Excalibur professional dehydrator (though it uses a larger fan, and would use more of them scaled up into your cabinet size, and the heating coil probably doesn't get nearly as hot as a ceramic heater but I still feel it would work).
Like this:
Edited by Hindsight (05/10/21 12:31 PM)
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filthyknees
no coincidence


Registered: 03/08/13
Posts: 6,283
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: Hindsight]
#27303478 - 05/10/21 07:43 PM (3 years, 8 months ago) |
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https://www.shroomery.org/forums/showflat.php/Number/25824371
I put a box fan in half way up to help push the air (plus the fan heater in the bottom).
Exhaust is passive out the top which was pretty limited but worked good.
-------------------- But if you're in a hurry, and really got to go
If you're in a hurry, might have to find out slow
That it's one thing to try and another to fly
You get there quicker just a step at a time
It's one thing to bark, another to bite
The show ain't over till you pack up at night
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sandman420
Saint PP



Registered: 06/17/04
Posts: 5,387
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: filthyknees] 1
#27303857 - 05/11/21 05:27 AM (3 years, 8 months ago) |
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it is best to have the heat at the back blowing horizontally. Way better. If blowing up, the top racks dry much slower.
Also how many watts you working with bud? You need about 4000 watts for a 5' dehydrator if you are going to stuff it.

edit: 600 watts? brother no. this is unacceptable...3000 watts would be anemic for this size.
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DERRAYLD
Constructus


Registered: 05/13/02
Posts: 12,109
Loc: South Africa
Last seen: 44 minutes, 46 seconds
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: sandman420]
#27303884 - 05/11/21 06:12 AM (3 years, 8 months ago) |
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Sandman bringing the info
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sandman420
Saint PP



Registered: 06/17/04
Posts: 5,387
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Re: 5' Tall Custom Dehydrator + Questions: Is it best to put the heat source on bottom w/ fan pointing up from the bottom or? [Re: DERRAYLD] 1
#27303899 - 05/11/21 06:23 AM (3 years, 8 months ago) |
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You will need a 240v 30A breaker to make this size of cabinet work right.
You can make the heating elements from nichrome80 wire.
You could use 12v 17" radiator fans or disassemble box fans (if they arent too wide for your cabinet, may be) for the motor and fanblade.
Probably 3 elements/fans if that route.
3d print insulating studs for bolts to go through to hold the elements around the fan.
Wire it all up to a PID
don't forget to ground the cabinet lol.
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