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Faith In Virginia 05-29-2012 03:20 PM

Temperature Monitoring Flow Chart
2 Attachment(s)
The first graph is the preheat of my oven for a bread bake the next day. It starts with a cold oven.

I have a 42 inch oven with 7.5 inches of thermal mass. the floor has 3.5 vermiculite/Portland insulation and the dome has 4" of ceramic.

I have 6 thermal couples (#4 is down due to wire connection problem)

#1 is center oven floor 3/4 inches from the oven interior.
#2 is center oven floor 4.5 inches from the oven interior
#3 is mid dome 3/4 inches from the oven interior
#4 is on the other side 3/4 inches
#5 is mid dome 4.5 inches from the interior
#6 is on the outside of the dome between the oven and the insulation.

You will note that I recorded the time at each measurement. I started the measurement at the end of the firing and left the coals in and put on the insulated door so the oven wall increased temperature after the door went in. You can see how long it takes the interior heat to migrate outward.

The second graph is the firing on bake day.

I started a medium fire at 08:00
Raked out the coals at 13:00
Loaded 11 each 1.5 lbs loaves at 19:36
Unloaded at 20:06
Loaded 9 each 1.5 lbs loaves at 20:55
Unload at 21:26

So this was quite interesting for me and it is a great help to know when I have enough heat for the oven. I find that if I average out the temperatures of my probes I can have a good idea what temperature the oven will equalize to. Nothing sucks worse then to have your oven too hot or too cold when your bread is ready to go in.

I hope you can follow my graphs I tried to put in the data that is in the spread sheet but it was unreadable when it got here.

When you look at the graphs probe #1 and #3 are 3/4 from the interior #2 and #5 are 4.5 inches from the interior and #6 is all the way out.

dvm 05-31-2012 07:55 PM

Re: Temperature Monitoring Flow Chart
Very interesting data - but it is bending my brain - can you graph temp on the vertical axis, time on the horizontal axis for each probe?

SableSprings 05-31-2012 08:46 PM

Re: Temperature Monitoring Flow Chart
1 Attachment(s)
I agree Faith, graphing temperatures for several bakes helps to provide you with a really good understanding of the heat loading/unloading properties of your oven. Very interesting to see how your data shows the heat moving into the oven. However, as DVM noted, sometimes a non-standard data axis bends our brains a bit...(and sometimes too much data covers up what we really want to see). Charting the probe temps (on the vertical) and time (on the horizontal) would really help show off the data you collected. What I really like about your data is that you could set up a table to use any one or two readings to get a good prediction of the entire oven's state of "readiness"...Fabulous!

I don't have any embedded probes, so I just took IR readings on "standard spots" in my oven to show how my hearth and dome's temperatures were related and "used" in a bake. (The Forno Bravo IR gun is terrific in that you can sweep an area such as the hearth or dome and get minimum, maximum, and average cool is that!) I discovered with my graphs, that in order to have a successful extended bake, my oven needed to have dome temps over 600F for 3-4 hours to fully heat load (for 15-25 loaves of bread). I added the "coals out"-clean & equalization time and baked item info on each graph I did to help correlate oven response during different bake days.

dvm 05-31-2012 10:23 PM

Re: Temperature Monitoring Flow Chart
I am constructing a 42 inch oven with a 19 inch dome height. (well so far I am constructing the stand for the oven mentioned above). I have a coil of thermocouple wire I plan to integrate into the build. Does anyone have recommendations on best practices for placing these probes? Can they simply be placed into the mortar between adjacent bricks? Is it better - or necessary to drill holes into the bricks for placement of the probes? I thought it would be good to check temps of the floor, the top of the dome, the side of the dome near the fire and the side of the dome away from the fire. I hope that I can collect and present data for my oven's design as well as Faith in Virginia and Mike have above.

Faith In Virginia 06-01-2012 05:12 AM

Re: Temperature Monitoring Flow Chart
Sorry for bending your mind. I will make up some more graphs from the same data.

What I liked about these graphs is that they show the overall picture in a 3D. Having three probes in the same section(one interior, one middle, one outside) and the floor has (one interior, one middle) So what I was looking at in this graph was the maximum of the interior to the minimum of the exterior and watching how they get to equalization. With the bake included, looking at the stored energy and how little it is affected and if you drop your wall and floor temp in a bake how will the oven recover and regulate.

dvm, I think I drilled some and others went in the mortar but I did not have them in solid. What I mean by that is they are in tight but if I need to replace them the can be pulled out and replaced without chipping or digging them out. As far a placement I had the same query when I built mine. I think I like my placements. If your main purpose is pizza your placements look fine. If you want to do some bread and long slow cooks you may way to get a probe on the outside of your dome to have an idea of saturation.

WJW 06-12-2012 08:43 AM

Re: Temperature Monitoring Flow Chart
Very cool Faith. (uh well not cool I guess). Good info though. I have three probes in place in mine and need to get my software loaded so I can get some good data.

As it is now I just wait until the outer edge of my bricks are up in the 575-590degree range before pulling the fire and cleaning out the oven for baking. It takes about two hours to get to that fully saturated point. The outer edge of the bricks continues to rise in temp until it hits the 650 range and then starts to slowly fall. In about thirty miuntes with the door open and the oven being mopped the interior will drop to the mid fives. Thirty minutes with the door on will equalize the temps in the 560-575 range and that's when I bake.

At least that's what I think...I'll have more exact info when I start collecting and graphng temps.


turkey 08-03-2012 07:41 AM

Re: Temperature Monitoring Flow Chart
HI Faith,

do you have the original raw data for this firing? I am very interested on the difference on the interior and exterior face of the firebricks during firing. Specifically the temp the insulation directly gets exposed to during the firing.

You graph is very helpful but its a bit hard to read and there are not so many data points to get a nice curve, i have no idea how you collected the data so not sure if there is more data or if it was a pen and paper job in which case you did sterling work to capture it all :)

Faith In Virginia 08-03-2012 10:11 AM

Re: Temperature Monitoring Flow Chart
1 Attachment(s)
Attachment 30756

This is the raw data. Let me post this and see if it is readable. Okay cool just double click on the little picture and it gets bigger. If you need me to refresh you on my probe locations let me know.

I hope this helps.


Faith In Virginia 08-03-2012 10:19 AM

Re: Temperature Monitoring Flow Chart
Looking at the #'s again I fired the oven the day before and left the coals in and shut the door took a number of readings after the door was closed then one the next morning.

The second set of #'s was after the firing and the temp drop as bread was baked.

Keep in mind my oven has 7.5 inches of thermal mass and 4 inches of ceramic blanket insulation above and 3.5 inches Portland/vermiculite under the floor (wish I went thicker)

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