Fine tuning 2x6 Waterloo flat bottom 7 section pan

[Willen]

I am a second season boiler, and upgraded from a 2x4 oil tank evaporator last year to a "proper" Piette & Fils Inc (Dunham, Quebec) old arch with a 2x6' Waterloo flat bottomed, seven stage serpentine flow pan. I feed sap at the stack end, and draw off the opposite corner over the fire. I am planning on adding a float box on the gravity feed line (I just turn it on and off periodically now).

Couple of questions:
1. How big should the stack be - it came with a 10" x 12' stack, and it REALLY draws, and I think I am losing alot of heat up this big pipe. It loses boil when you open even one of the doors quickly to put in a few sticks of wood, again because the pipe is so large, and there is no damper. So I am going to add a damper and see if that helps, but wonder if the pipe should maybe be 8" or smaller?

2. How much gap do I leave between the bottom of the flat pan and the top of my insulation/sand in the flat area of the stove after the "ramp" of the firebox? I've got 2-3" now.

Thanks very much for your help!
Scott.

2019 - 60 buckets, 85L of syrup
2020 - 100 buckets, 60L of syrup and counting.......

[ecolbeck]

I believe that an 10” pipe is standard for a 2x6 but someone else with more experience will chime in. Having strong draft is a good thing because that is what drives your fire. Yes you lose heat up the chimney but that is the cost of doing business. Slowing the draft (by using a damper) will only result in less heat production. It is normal for the boil to slow when you open a door because of the influx of uncontrolled cold air. Keep the reloads quick and you’ll be in good shape.

I would shoot for about 2” underneath the pans. It sounds like you are pretty close already.

[maple flats]

Losing the boil or reducing the boil when you open the door to add wood is quite normal. For best results, have your wood to be added set up close by, so when you open the door you can get it in and close the door as fast as possible. Just be careful not to hit the bottom of the pan and cause a dent.
When I add, I have the wood set right next to the door, then I grab the wood in 2 or 3 double hands ful, toss it in and have the door closed again. I try to have it open less than 30 seconds.

[maple flats]

For space, you likely have about 23" wide opening. Pi R squared is 3.14x25=74.5 sq ", divide that by 23 and call it 3". If you had flues you usually only want 1/2" to 1" space, forcing the heat thru the flues. In fact, with a flat bottom I would even try a 2.5" space. Do not add a damper, those are for wood stoves to slow the heat and the burn, on an evaporator the key is to make it burn as fast as you can.