As I mentioned in this post:
http://www.smokingmeatforums.com/forum/newestpost/83549
I am having some trouble with getting the temperature to where I need it.
I have two hot plates 1000W and 900W and without modification they don't seem to be able to do the job.
I think my options are:
1. Insulate
2. Override the hotplate thermostat and let my PID controller do its thing.
Ben,
I got your PM and here is my take on the two threads in which you describe your issues. I'm not the know all and end all source and this is just my opinion.
Insulation would help with heat retention and also let you run the smoker with a smaller wattage element. I don't know if a 1000 and a 900 would work together very well and you would probably have better results with a single 1,500 watt element like the brinkmann model that runs about $39 on
Amazon.com.
Since you indicated the SSR is never shutting off and the hot plates are both cycling - your main problem is the thermal limit switch in the hot plate bodies. Each of them should have a small "switch" that opens at a set temperature cutting the power the the plate to prevent overheating and a possible fire. Due to the enclosed environment, this switch is kicking in and cutting the power to your heating elements. In essence the thermal limiter is setting your temps and not the PID (which is why the SSR never shuts off). Having both hot plates in the smaller enclosed area below the plywood with the vent holes exaggerates this effect. I bet if you took the temp of that chamber (the hot plate chamber) you would find it is a lot hotter than the temps in the meat chamber.
I'm leery of having that dividing sheet of plywood with the holes between the two chambers. I would be more comfortable seeing either large ceramic tile squares or cut cement board (Hardie board or similar) lining the bottom and sides around the hot plates. I would then think about a sheet metal tent you could foil and keep food drips off the hot plate(s) and your smoke source. I would rather see a metal grate (like meat grates) if you want to put a drip pan where the plywood divider with holes is now. It will allow better heat and smoke flow and not be prone to combustion/charring.
Try taking the plywood sheet with holes out, remove the thermal limit from the 1,000 element and see what sort of temps you get then (and I still really think you need tile or cement board to protect the plywood around the heating element, no matter what the wattage is).
Another suggestion I would make is since this is a plywood box and you are talking about having it on or close to your home, I would add a 2nd PID controller to act as a safety cut off if the temps go above a certain point (add a smart thermal limiter of your own). This would be a fail safe if the SSR or PID failed and the electric elements were in a run-a-way "on" type situation. In essence it's a 2nd PID and SSR who's temp sensor must see chamber temps below the "fail safe" set point. If the temps are below the fail safe point, the rest of the circuit (the smoking PID, SSR & heating element(s) have power and can do their thing). If it goes above the fail safe point (ie, something is wrong), it kills all the power to those parts of the smoker and prevents your house from burning down after the wooden smoker catches fire due to a run-a-way temp situation. This would also kill the power if you had a grease fire. I would not put out the grease fire, but it would kill the electric current and take the primary source of ignition away. It might still be self sustaining, but it will have limited air supply and will probably choke down quickly. You could still use the alarm function on the smoker PID, but having a fail safe set above the other PID's alarm point would be a good idea IMO.
I know there are quite a few wooden smoker owners on SMF, but I'm just leery of an unlined wooden smoker if you are going to warm smoke above say 170-180* (and I would not even consider going above the low and slow temps in the 225* range - forget about poultry at 375*).
