After making boiling sap with out steam table pan maple syrup evaporator for 2 seasons now, I have a few thoughts on improvements. The build videos for our homemade maple syrup evaporator are here. Watch the update video below:
How To Improve the Steam Table Pan Maple Syrup Evaporator
I'm not sure why I connected the chimney stack about 6" below the top of the cabinet. But I think the air flow might improve if the smoke exited higher up, in addition, the hot air would wrap around the back pan more. Also, consider a higher chimney pipe, it will cut down on the smoke the downdrafts on top of you.
For the turbo fan, which really womps up the fire, consider connecting it just below the fire door. I plan on adding a dimmer switch in the power cord, since controlling the fan speed is important. You can find bathroom fans at tag sales or in your neighbor's garage.
For most 4 drawer letter sized file cabinet, two regular sized trays fit, but there will be space. As a result, that gap needs to be filled in with a scrap piece of metal or a small food tray. Put this small space above the fire door, and move the pans closer to the chimney. Because your fire is moving toward the chimney, the hottest part of the fire is on that end.
I found that putting the fire grate about 10-12" below the steam table pans worked for me. It depends on the kind of fuel you are burning, consequently, adjust yours to the size of the wood. We burn pallets, which slide uncut into this evaporator. 
This homemade maple syrup evaporator gets really hot, so be careful when standing near it. For our next evaporator build, I may line the sides with firebrick.
If you are thinking about buying a real evaporator pan, read our post here.
Dan
Hi Eric,
You inspired me to make my own file cabinet evaporator. I just fired it up this morning and had water boiling in 35 mins. I decided to put a flue inside mine so the heat would stay close to the pans. I also didn't sink the pans right inside to avoid scorching hopefully. I am very pleased with it and thank you for showing the how to on your channel. Waiting patiently to see your new evaporator with the legal sized file cabinet. I would share pics of my evaporator but can't seem to paste them in this message. Happy sugaring this year
Regards,
Dan
Steve Seitz
Hey Dan-Planning g on building one from a fireproof file cabinet which is already lined with firebrick-may cause some issue with cutting out door & flue-but we shall see—Also wondered about having and ash door below the loading door to remove ash build up? Thanks for your videos-very Inspiring-This will be my third year for making syrup-but I make my syrup from Black Walnuts-nice nutty flavor-Thanks Steve
Steve Seitz
Hey Dan-Could not find your link for the guy Who makes the new evaporator pan? Also did u have to raise the fire since this pans does not sit down into the cabinet-Thanks for your help
Eric
@steve here is the link to the guy who makes custom maple syrup evaporator pans http://maplesyruppans.com/
Tim
my first evaporator I built was a 55 gal metal drum w 2 pans also but they were turned sideways . It is the Same principle as your set up but a smaller more compact unit which I think was easy to move by myself and store. But I acquired a new 2’x4’ stainless tray which I will also be utilizing this year somehow. I think this set up would be great for that and cheap to build. But I wanted to know if the fan helps that much. Thanks. I tried to post a picture but can’t seem to get it loaded.
Eric
Hi Tim, the fan does OK, it helps when you are first starting up the fire. see this new post about a new design my friend made : https://gardenfork.tv/file-cabinet-maple-syrup-evaporator-photos-friend/
Eric
Hi, I love this idea. I am wondering what your level of concern, if any, was with burning in / boiling over a file cabinet in terms of chemicals released from the paint when exposed to heat. I have two young kids who love homemade maple syrup but would hate to expose them to anything harmful.
Thanks for sharing!
ALLENS
I was wondering about installing a secondary heat feature (basically pipes with holes to "inject" air to back chamber. On a wood stove this increases temp, plus reduces wood consumption.
bill
we use short pieces of copper tubing bent into a U shape as a siphon from pan to pan. This way it slowly adds sap from warming to the cook pan, you can also put one between the pans to make a continuous flow arrangement. You start the siphon by dipping it in cold sap, plugging an end with your finger and placing each end into the sap in both pans, release finger and the siphon will self level the depth between pans. Also add cold sap with a slow trickle to the warmer from an elevated barrel with a valve. If you size the tubing for the evaporation rate you will push finished syrup to the front pan in a chain and not kill the boil.
Your firebox is too big, close off the back half and raise the it to within 3-4" of the pan