Thermocouple help

[Caleb]

Hi folks,

I've been working on my pizza oven for the past month or so and am ready to pour the hearth. However, I would appreciate some advice on how best to install a thermocouple, as well as the suggested model to buy. I was planning to run some copper conduit through the hearth as I pour the concrete so I can easily run the thermocouple wire. Is this a good approach?

Any suggestions would be much appreciated.

Caleb

[rlf5]

I didn't make any provisions for my thermocouples. Rather, I just drilled the holes for them after I was finished.

[Mojoe]

I used stainless because of the heat exposure and resistance to corrosion. I've seen numerous discussion on Omega thermocouples, give it a search in the forums.

[dbhansen]

I am using model #TJ36-CASS-18U-6 from Omega, as recommended by one of their engineers. So far so good. I have one running through the hearth under the oven floor, and right now the wire runs along the bottom of my hearth (along the roof of the wood storage area) and then back up through the hearth to reach outside the oven. I think the conduit would be a great idea, as long as it doesn't weaken the hearth. I used two 1/4" copper tubes running vertically through the hearth, and they got bent all to heck. I had trouble getting the probe to fit through it.

[Caleb]

dbhansen,

Great photos and oven! Thanks for your feedback. Can you tell me about the interface with your oven bricks and the thermocouple tip? This looks like it could be a tricky maneuver.

[dbhansen]

Originally Posted by Caleb

Can you tell me about the interface with your oven bricks and the thermocouple tip?

I'm not quite sure what you're asking, but basically the thermocouple probe extends through the concrete hearth (4"), through the insulation board (2") and about another 1.5" into the middle of a floor brick. The probe is composed of a stainless-steel sheath over (and bonded to) the two thermocouple wires, and the sheath is in direct contact with the brick. The thermocouple wires themselves do not touch the brick. The "U" in the product code stands for "ungrounded," which has something to do with the thermocouple/sheath interface, but don't ask me what! It was the recommended way to go.

Daren

[nissanneill]

Caleb,
unless you want to bake a host of bread, I wouldn't worry about using the thermocouples.
I put in several in the floor and the dome and don't use them at all. I fire the oven for between 2 to 3 hours getting it to over 500˚C (the limit of my laser thermometer) and cook pizzas, then breads and finally a roast lamb and sweats. The oven is still hot next morning even without good insulation on my doors (my next project).
I purchased a 10 station thermocouple switch from the UK, placed all the wiring copper conduit/tubing into the oven and it is all a waste really of time, money and effort.
Hendo has a posting with his thermocouples and I think at this stage that they will not be used. Sure he would have installed them but the family initially are not but they can when needs permit as they were designed to be accessible and their locations are together with cable access to a reader.

Neill

[Caleb]

Thanks for your input Neill. I anticipate baking a lot of bread as am an avid, albeit, ametuer baker. I think I may purchase enough to have 2-3 thermocouples (2 in the floor, in the dome). Hopefully that is not too ambitious. I'm gathering my photos of the project and will keep the forum posted... its always good to pass along one's own experience.

[nissanneill]

Caleb,
you usually have 2 thermocouples together in specific areas of your oven, one to measure just below the hearth surface (or dome) and another at the bottom of the brick to measure the amount of heat retained (soak). I have 2 lots of themocouples in the floor and 2 sets in the dome. I can measure the centre of both at their surface and their soak to calculate (established through trial, error and experience) the amount of cooking I can achieve without a fire in the dome.
After you have used the oven for a period of time, you use the laser thermometer and experience more than the thermocouples. but by all means put them in, learn by them but don't spend a fortune on the equipment. The thermocouple wire is quite inexpensive but not so the reader. I got mine from my son for free so all up cost for my set-up was only around Aus$50.

Neill

[dbhansen]

Caleb, one option for a reader is an infrared thermometer that also accepts thermocouple inputs. Have your cake and eat it too, as they say. You can get one for about $100 or less.