Room under drop flues?

[Motoman89]

Hi all, I have an 18 x 66 CDL evaporator and I am wondering how much space I should leave underneath my flues? I was advised by the rep to add sand to the bottom of my arch on top of the bricks to bring up the height to within a quarter of an inch of the flues. Originally I was trying to boil an Originally I was trying to boil in a lien two and was having trouble getting my serve pan and my flu pans to boil hard. Just wondering what other people have done and what results they have seen?
TIA

[Bricklayer]

Sand is not the best thing to use under the flues. We tried it a couple times and it always ended up being pushed or blown down the arch and piled up basically touching the flues. We rebuilt it 2 years ago and used ceramic wool blanket on top of the sand. Made a world of a difference. We have about 1/2”-3/4” below the flues. Boils like crazy.
If you can’t get ceramic blanket then Roxul ( mineral wool ) will do the job in a pinch.

[Backyard boiler]

I have the same rig. I tried going 1/4 and syrup pan boiled great flue pan however would only boil in the front. On that set up I averaged about 10-13 gph. I kept taking 1/4 of sand out at a time until I got to about 3/4 of an inch from ramp to end of flues. From end of flues to base stack I took all the sand out so just brick I have been averaging 20-24 gph and flue pan boils hard from front to back. Syrup pan boils first on start up and boils great. I invested in a Smokey lake stack temp probe and that was one of my best investments I get a hard boil around 650-700 degrees. The sap will jump out of flue pan! Hope it helps

[ecolbeck]

I suggest only having bricks in firebox area of the arch to protect insulation from damage. Otherwise bricks are unnecessary and contribute to a slower warmup and cooldown process.

[Motoman89]

Hey BB, I had to slide both my pans to the rear and put the piece of “I” beam at the very front or my syrup pan didn’t really work as it would slope upwards and then we would make syrup in the first section of the syrup pan and the draw off section was really hard to monitor the temp and syrup. My syrup pan also struggled to boil well until we did this. The CDL guy was not much help for advice so this is what we ran with. Did you have this issue? Maybe my unit was just built after some wobbly pops on Friday afternoon and they made a couple of minor errors.
My thermometer ports are also way off and I can’t really use them with a normal thermometer. Had to cut off the adjustment tab just to get it to thread in or it would hit the pan on the first turn once you set it.
Thanks for the info and I may bug ya with a few additional questions if that is ok with you? I will try lowering my sand today when we wash and see how it goes.

[Backyard boiler]

Little rigs are hard to run. I have been tinkering on mine since I got it 2 years ago and finally got it where I like it. I had a Similar situation with Cdl for help until the new manager took over he had been for ever helpful can even text him a question and he reply’s. I have found it is hard to make light syrup on this rig but maybe a blower would help. Is your wood really finely split? Iv also found I build up a big fire for the 1rst 20 or 30 minutes than I let it die down a little and mainly only fill the fire box a 1/3 full or one lay of wood and coals and a couple small pieces on top I have noticed I get more frequent draws this way.

[ecolbeck]

I find that the only way to reliably make syrup on mine is to block off the connection between the pans and then open it periodically to push the sweet towards the drawoff. There’s too much mixing between the pans if I don’t do this.

[Backyard boiler]

I struggled with syrup in my old 18x48 but Cdl worked out a deal with me on a trade in for the new 18x66, i can pull syrup off every 15 minutes or so once up to temp. Sometimes can’t get it off quick enough and comes off a little heavy but I always draw off into my vacuum filter so I adjust if I need to with my Murphy cup out of the filter tank. It was a lot of guess work at first, I wish Cdl would update instructions for one and would have more time in the hobby zones, although I think they have started to show more Interest in it

[maple flats]

I filled under my raised flues using Vermiculite, capped with half bricks so the top of the bricks was about 1/4-1/3" under the flues, worked well for years. When I sold the evaporator it had settled to just under 1/2".
Vermiculite (get it from a greenhouse supply house, not a garden center, huge price difference).