Electric heating of my WFO

[SCChris]

Re: Electric heating of my WFO

V12, My oven is 43" with 2" inches of rigid Ca/Si insulation under the floor, a heat break between the oven floor and the landing, about 4" of Stone Wool over the dome and entry areas with loose vermiculite and fiberglass insulation in the corners of the oven house. The total depth of insulation over the top of the dome is somewhere about 9-10 inches. The oven floor is standard firebrick laid flat 2.5 inch thick, the walls are 4.5 inches. I have no heat break between the oven dome and the entry area.

Typically the cooling profile is;

150F drop / 24 hours at temps higher than 500F,
100F / 24 hours at the middle temps 300-500, and
75F / 24 at the sub 300F temps.

The time post pizza burn, with daily cooking access, that the oven is above 200F is 4.5 days +/- 12 hours.

Chris

[v12spirit]

Re: Electric heating of my WFO

Chris,
Could you tell how much does the temperature of your oven fall per hour when sealed at a given temp with no heat source in it even the electric one? what is the size of your oven and the thickness of the dome bricks?

[SCChris]

Re: Electric heating of my WFO

The readings from 150C/302F are that my oven requires 0.5 kWh / Hr to maintain this temp. From $0.09 to $0.19 per hr. depending on the rate tier.

The readings from 120C/248F show a demand of 0.35 kWh / Hr, or $0.06 to $0.13 per hr.

Chris

[SCChris]

Re: Electric heating of my WFO

David, I'm with you on the off grid, self sufficient and renewable parts, but unfortunately for me, paying for wood isn't something that I can fully avoid.


Chris

PS David, it would be sooo nice to have a wood lot!

[david s]

Re: Electric heating of my WFO

I've never paid for wood on principle. My feeling is that a WFO uses renewable fuel that is obtainable anywhere for nothing if you look. It is easier for me as my oven is very small and fuel efficient, but I like the idea of stepping off the grid and being self sufficient.

[SCChris]

Re: Electric heating of my WFO

I acquired a new plug-in power meter and hooked up the PID controller. I was shooting for holding the oven at 475F/247C +/- but decided that 446F / 230C was well above the temps that I’m practically interested in. The power draw for the last 3 hours while holding 446F, was 0.912 Kwh/hr or about $0.32 per hour, this calculated at the highest rate tier of $0.35/Kwh as charged from my electric company.

The 475F is attainable, but the cost in grid electricity is not economically acceptable to me, at least not as an anything other than the last option. If I were to use solar panels, this 0.91 would demand something like a 3Kwh system. This assumes that the panels will only provide power for 8 hours during winter and that the power would be battery stored and used during non-generating hours. A 3Kwh system would require something like 12 250W panels, this a small to moderately sized installation and definitely more dollars than I’m willing to dedicate to a constantly very hot oven.

I’ve dropped the control temperature to 302F/150C to see what the power requirement to hold at this temp is. 250F to 300F is really where I envision my best holding temp to be, I hope that it’s high enough to be usable for many requirements but low enough to maintain at an acceptably low cost.

Ok. So "If" I'm doing the math correctly.
912 Watts = 3112 BTU, and Oak, Oregon "Garry", contains 6211 BTU/Lb - so 0.5 Lbs, or 227g of this Oak roughly contains the required input of energy to maintain 446F, in my oven. This is really a bit misleading in that the oven needs to have available oxygen and be able to vent the combustion gasses and with this open environment some of the heat. I'm again amazed at the energy contained in firewood. Another point that was mentioned earlier is that the heat storage, the brick mass, isn't really a great benefit for an electric oven other allowing for rebound to a temp after opening and closing the oven.

If I pay $250 a cord this is $0.07 per Lb and 6211 total BTU. $0.07 for wood or $0.35 for grid electricity, it's pretty clear that even with the loss of energy during a burn, it's hard to not to be money ahead by using wood.


Like I mentioned above, I have the thermostat of the oven set to 302F/150F and should have some numbers on the power requirements to maintain this temp by Wednesday afternoon or Thursday.

Chris

[SCChris]

Re: Electric heating of my WFO

Bitter soot isn't something I aspire to accomplish. It wouldn't take much to put together a wood door with vent holes top and bottom and as long as the temps are low and the smoke container isn't too close, wood should be fine for a while at least for the 250F range.

Thanks again all.

C

[Gulf]

Re: Electric heating of my WFO

Gulf, I expect that I'll need to play with it for awhile and cracking the door may be needed to allow a slow burn of the wood chips anyway. Slow roasted pork is always better than no pork. ��

Chris

I agree, but a great taisting slow roasted pork is even better. At todays prices for pork and beef, I would not stagnate that smoke in my oven. I have "been there and done that" in mine.

Unless, you incorparate a special door with a piping system, from the bottom of the door, to the interior of you oven, and an outlet at the top of your door to the flu, you probably wont be satisfied with your results.

What I described earlier was a homemade lump charcoal. (made from any kind of smoking wood you choose) It will give you some wood fired flavor, but without the bitter soot taiste .

[GianniFocaccia]

Re: Electric heating of my WFO

But, the most important thing, is that it needs to be moving.

I agree. FWIW, my pulled pork shoulders go into a 280F oven along side an expanded metal charcoal basket with a 'log' of lump oak charcoal carefully piled into the bottom of it. I light one end of the log and, leaving the (uninsulated) door barely cracked, don't have to replenish the charcoal for 3 hours. There is enough airflow to complete a very slow combustion, and enough residual heat in the dome to get the 8-9hr job done. The meat comes out surprisingly close to my shoulders done in the offset smoker, only with a whole lot less work during the burn.

I would imagine that a 300F saturated oven really doesn't care where it got it's heat from...

[SCChris]

Re: Electric heating of my WFO

Deejayoh, one thing about low temp roasting, a highly insulated door isn't going to make a huge difference. I'd like to find a convection oven to scrounge a few parts from and the fan door gasket and heating element come to mind.

C

[SCChris]

Re: Electric heating of my WFO

Gulf, I expect that I'll need to play with it for awhile and cracking the door may be needed to allow a slow burn of the wood chips anyway. Slow roasted pork is always better than no pork. ��

Chris

[deejayoh]

Re: Electric heating of my WFO

Chris,

One thing you will probably find is that you don't need very much smoke. It needs to be a light thin blue, to almost invisible. But, the most important thing, is that it needs to be moving. You need an efficient source of air to the chips, and an exhaust some distance beyond the meat to accomplish that.

A sealed oven will allow soot to settle on the food. It won't taiste like you expect it too . You may have to expeirment with a partialy opened door. At the least, I would preheat the chips, to almost a char before placing them in the hot plate .

Sounds like a small fan is still required? I guess you could rig the whole contraption onto a door. Heater, smoker chip tray, fan. Run a thermocouple to the center of the oven to measure temp. Probably getting ahead of myself, but I like to think out loud.

[Gulf]

Re: Electric heating of my WFO

DeeJayoh, I'm thinking about the smoking aspect as well. Once the oven comes to temp, say 250F for a pork butt, it'll be interesting to see if whatever is sitting on the hotplate gets hot enough to start and hold some smoking chips, and if the chips will stay lit in the sealed oven. With what I have done so far, I'm comfortable that holding any temp from 200F to 400F is doable. economic, I can't say, convenient yep. In your area, firewood has got to be pretty cheap, not so much here.

C

Chris,

One thing you will probably find is that you don't need very much smoke. It needs to be a light thin blue, to almost invisible. But, the most important thing, is that it needs to be moving. You need an efficient source of air to the chips, and an exhaust some distance beyond the meat to accomplish that.

A sealed oven will allow soot to settle on the food. It won't taiste like you expect it too . You may have to expeirment with a partialy opened door. At the least, I would preheat the chips, to almost a char before placing them in the hot plate .

[SCChris]

Re: Electric heating of my WFO

DeeJayoh, I'm thinking about the smoking aspect as well. Once the oven comes to temp, say 250F for a pork butt, it'll be interesting to see if whatever is sitting on the hotplate gets hot enough to start and hold some smoking chips, and if the chips will stay lit in the sealed oven. With what I have done so far, I'm comfortable that holding any temp from 200F to 400F is doable. economic, I can't say, convenient yep. In your area, firewood has got to be pretty cheap, not so much here.

The PID was another fun diversion, I've done short ribs and they turned out very good, but I'm not convinced that Sous Vide is really my kind of cooking..

V12, If I post pictures it'll remind everyone of Frankenstein's wiring closet.. Ugly! I'll get it tidied up and pretty for pictures soon.

C

[v12spirit]

Re: Electric heating of my WFO

Interested to see the results. Send some pictures for your experiment.