I hope that some of you can check my planning process in laying out the basics of a stainless steel fridge smoker build. I'd appreciate any insights.
The smoker will be used for cold and hot smoking with a max temperature of 225 F. If I want to do traditional BBQ I'll light off one of the several smokers we have. I see this as primarily for sausage, hams, bacon etc.
The insulation is polyisocyanurate which is rated to 300 F so I plan on leaving it in. The walls have a hair over 2-1/2" of insulation and the door has a hair over 1-3/8" of insulation. Figuring the insulation vale at R6.25/inch and the average thickness of the walls, top and bottom the average R value of the cabinet is just under R14 not counting the two layers of stainless steel.
The interior measures 22x26x60 inches so it is just under 20 cubic feet. Playing with a 200 F heat rise to account for cold days a couple of different calculators average results come out to about 4400 BTU/1300 Watts per hour. I figure on at least double that for loss out the exhaust, opening the door, faster temp recovery etc so that leads me to a minimum heat element of 2600 Watts so for giggles and insurance maybe a 3000 Watt element? I think I did the math right but any help would be appreciated.
There is 30 Amps of 230 volt at the smoker location so power is not an issue. Even with a 10% de-rate there are about 6000 Watts available.
We'll be using a PID controller for heat and at least two probes.
I plan on an AMNPS for smoke and will locate that over the air intake to be sure it doesn't get starved for oxygen.
My thoughts for the intake and exhaust are around 4" intake and 4" exhaust, both with dampers.
I'm thinking of using the top 2/3 for smoking so that leaves me about 20" at the bottom for the AMNPS, heat element, baffle plates, etc. I'm thinking of having the AMNPS at the bottom with one baffle plate, then the heat element with another baffle plate. The element will be centered in the unit.
I think I will use a drip pan on a shelf under the product as needed rather than try to build something in that forces the heat to the outer walls.
I want to have fairly tight control of the humidity if that can be done without getting to the stage of over complicating things. I'm most concerned about being able to stay in the 75-85 % humidity range for cold smoking. I'm looking for any advice on how to manage that. Maybe with a humidistat and removable ultrasonic humidifier?
The refrigeration unit still works so I'll disconnect the controls and pop it off the top of the fridge and save it.
So, after all this long windedness the questions are: Does a 3000 Watt element sound about right? Any thoughts on humidity control? What am I missing?