Sledhead, I have a stalled in-progress insulated warmer conversion sitting out in our shop. I expect to get back to it after deer season. I don't want to hijack your thread but you seem to be heading down a similar track as me.
In my warmer the original 200 degree F, 1650 watt, 120 volt unit has a heater and fan unit as a removable package unit wired with the fan control independent of the heat or humidity elements. I expect to pull it out for smoking.
The gap left below the door (where the controls are on the package unit are) would be a good place to add a removable pan with the 240 volt element and an adjustable front intake vent panel. I plan to use a top exhaust stack with a little drip pan suspended under it to catch any drips from moisture condensing in the stack. I think the stack unit pictured above would work just dandy.
The electrical modification will use a 240 volt 2,600 watt element directly driven by an Auber WSD-1500GPH plug and play smoker controller. The element will draw 10.83 Amps/240 volts at full load and the controller (120/240 volt capable) is rated at 12 Amps continuous load so at 240 volts the element is getting close to the max continuous output rating of the controller. All of which caused me to wonder if the controller might eventually overheat if driven at full output for a long time.
I'm often a belt AND suspenders guy so after discussing my desire to cool the controller with a computer type fan I was advised by Kane at Auber to have the fan blowing on the heat sink which is located on the bottom of the controller. That way the unit could easily drive the element at full power on a hot day with no issues. The current plan is that the fan will mount under the shelf holding the controller and blow through a vent onto the heat sink and the fan will be running whenever the power is on. I found the 120 volt variable speed fan on
Amazon for (if my memory is correct) around $23 USD.
Auber has the ASD-1500GPH on sale for $203 USD right now and that includes two probes-one each for heat control and for your product. For a ready to run plug and play unit that is fully programmable and which will run an auxiliary device like a smoke generator on a program that's a good deal. The 120/240 volt capability is a nice bonus. You can read about the 1500GPH at:
http://www.auberins.com/index.php?main_page=product_info&products_id=381
Regarding running the WSD-1500GPH on 240 Volts, what's below is cut-and-pasted from Kane in an Auber email....
To use WSD-1500GPH for 240VAC power supply, since the 120V power plug is different than 240V, you need to cut the original plug, then install 240V plug, or you can use special made power strip/adapter to convert the power plug for 240VAC. The original power plug is NEMA5-15P. This controller needs three wires from 240V power supply: two hot wires and one ground. No neutral needed. The heater output socket is NEMA5-15R. Smoke generator socket is IEC C13.
The maximum current output is 12A/240V. Please make sure the power rating of your heater is less than this rating. Also, when you power it by 240V, both heater output and smoke generator output will get 240V as well.
If I feel I need to circulate air while smoking/cooking I've contemplated using a variable speed squirrel cage fan pushing air into the vertical louvered stack on the back wall and pulling air from the smoker. Like this one maybe:
The advice to leave the exhaust flowing without restriction is generally good advice for combustion heated units running on charcoal, wood or gas as they need a lot of airflow to both support combustion and to keep the smoke from getting bitter. But from my experience that does not apply to electrically heated units so regarding a dampered exhaust, I would install one. A smoke generator drawing it's combustion air from inside the cabinet, like the
AMNPS or tube units, will need more air flow than an external smoke generator will but in any case it will not need as much airflow as a combustion fired unit does. The adjustable damper gives you options and more control.
If you use an external smoke source you need very little air flow so long as you have enough to exchange the smoky air. We have three electric units now, none as big as the warming cabinet, though. If seeking to dehydrate while smoking (such as for jerky) I usually keep the vents wide open. For hot smoking and BBQ we keep the vents wide open until the surface of the meat or sausage is dry and then continue with them around half closed which, in addition to using less energy lowers moisture loss. I will note that getting a good bark on the critter parts requires the damper being more open in the later stages of BBQing.
Lastly, a cabinet like this won't necessarily be used for smoking all the time so if you are using it for plain old cooking or reheating then closing the vents will heat your cabinet and food faster and with less moisture loss.
I hope all this rambling helps.....
Lance