Thermometer depth

[CharlieVT]

First, thanks for all the info I've gotten off this board.

Question about thermometer depth: I've read previous posts on the subject but still have questions.

I have a 4x10 two sided reverse flow, wood fired evaporator (I converted from oil), forced draft, with hood and preheater over raised flue pan. I've read recommended depth in syrup pan is about 2 inches.
My draw off thermometers are parallel to the bottom of the pan about 1 1/4 inches off the bottom.
Does this sound like the right depth for the thermometer?
I am adding thermocouples for a home made auto draw off and am wondering if I should use the same distance from the bottom of the pan.

Any observations or suggestions appreciated. Thanks in advance.

[adk1]

there should be a mark on the thermometer stem (line) that is supposed to be covered with sap. I would go by that.

[maple flats]

I never ran that deep, but you will get an accurate reading as long as the stem is covered with sap but not in contact with the bottom. My old syrup pans had thermometers in the side of the pan and held the stem parallel with the bottom, about 1/2" off the bottom. I'll be experimenting with my new pan because the thermometer mounts are up above what my syrup level will be and they slope downward a little. Both mounts are in the draw off boxes and point to the passage hole leading to the syrup pan. I likely will need longer stem thermometers than in the past. I haven't studied nor asked Thor yet (they made the pans). I'd better get going on that real soon.

[spencer11]

i kinda had the same question, i would have to run my pan around an inch and a half deep, which i thought was a little deep? any more info on the homemade auto draw off?

[CharlieVT]

I never ran that deep, but you will get an accurate reading as long as the stem is covered with sap but not in contact with the bottom. My old syrup pans had thermometers in the side of the pan and held the stem parallel with the bottom, about 1/2" off the bottom....

Thanks for the reply. I wondered about depth. (I'm kinda new to this, ran this evaporator on oil last year, converted it to wood this summer). I've been reading; got a booklet: Boiling 101, by a gent from Leader who has given presentations at Bascom's open house events. Used the formula in his booklet for depth, size of pans + enhancements. I realize 2 inches is a little deep, but I rather have some dark syrup than a burned pan. :lol:

The thermometers that were installed in the pan when I got it were installed 1 1/4 inch above the bottom of the pan. I thought that might be a little high since it seems to me minimum depth would have to be 1 1/2 inches or the thermometers would be too high. That's why I was wondering if I should put the auto-draw off thermocouple a little closer to the bottom of the pan. It would allow me to run a little more shallow.

Prior owner of this evaporator was finishing in the evaporator. Since I'm going to be firing and drawing off single handed, I decided I'd be better off as a newbie trying to get an auto-draw off set up for drawing off light and then finishing in a finishing pan.

I'm in the process of putting the thermocouple in, which is what prompted my original question. Your reply: "...long as the stem is covered with sap but not in contact with the bottom..." is what I thought the right answer was, but I was looking for confirmation. You confirmed. Thanks.

[CharlieVT]

i kinda had the same question, i would have to run my pan around an inch and a half deep, which i thought was a little deep? any more info on the homemade auto drawoff?

Regarding depth: given what I think I know from reading, 2 inches is kinda deep but that's what the "eggspurt" has suggested is advisable for my forced draft, 4x10, raised flue, with preheater and hood. With my thermometers mounted 1 1/4 inches above the bottom of the pan, I can't see running less than 1 1/2 inches.

I do plan on posting about what I learn with my auto-drawoff efforts. I got my start building my home-brew drawoff from reading posts on this board. I have some experience with electronics so am somewhat comfortable experimenting with this.

Here's what I have so far: This is the control unit:
http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=237

This control unit is relatively cheap compared to the commercially available maple industry specific drawoff units, and allows for alarms to be programmed at any temp desired. (I'm planning of setting the high temp alarm 3 degrees F above the draw off temp, although I have read that some folks advocate 2 degrees above draw off.) Additionally, various parameters can be programmed to try to improve control of drawoff temp. I also plan on wiring my forced draft blower to shut off if the high temperature alarm is reached. Understanding and wiring this unit does require spending some time to understand the manual. The complexity of the unit follows from the number of parameters that can be controlled by the user.

This is my thermocouple:
http://www.auberins.com/index.php?main_page=product_info&cPath=20_15&products_id=270

After doing some online research regarding solenoid valves, I decided I'd just use one of these:
http://www.thebbqguru.com/products/3%7B47%7D4%22-12V-Stainless-Steel-Solenoid-Valve-for-Maple-Guru.html

Since the solenoid valve I selected is 12volt DC, I needed a 12V DC power supply which is switched by the control unit. A 110 volt AC solenoid valve would have eliminated the need for the 12 Volt DC power supply, but I wasn't able to find one that met the requirements of both food grade and temperature tolerant at a comparable price. If someone knows of such a valve, please post your findings.

The cost of these three components is $181.35 plus whatever tax and shipping costs are involved. Additionally there is the cost of a 12v DC power supply (I had one so didn't need to buy one.)

If what I think about this combination of components is correct, it is potentially a cost effective alternative to a basic Marcland unit. I believe that it has the advantage of high temperature alarm and blower and/or burner control over what the Mapleguru offers. It will not have the porportional control or atmospheric pressure correction of the higher end Marcland units. Additionally, this home brew setup will not be as "plug 'n play" as the commercially available units; clearly the vendors of these commercial units have done a lot of homework and deserve compensation for the time and energy they put into developing their products. For those of us willing to experiment and try to cobble together a low cost alternative, I'll post the results of my experimentation. I realize this will require careful attention to thermometers and hydrometers to see how the home brew auto-draw off is behaving. Again, I'll post my experiences with this home brew auto-draw off, but that'll have to wait 'till the sap is running....

[heus]

Thats why I liked the thermometer port on my former Phaneuf 2x6. It was at an angle so I could run various depths in the syrup pan. On my new evaporator the port is parallel with the bottom of the pan, but at least is pretty close to the bottom without actually touching.