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Old 10-30-2007, 12:32 PM
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Default Thermocouples: what kind?

Dear All,

Would a cheap thermocouple like this eBay item 190162283127 do the job? Do I need to shield it from the cement/mortar with a tube of sorts? Would have to be teflon or something similar.

And also, they come in different temperature ranges. Will the one with 250 deg C maximum do in the dome? How about 350 deg C (eBay: 190108496235)? Anything more and the prices go up fast.

Any experience? Maximum temperatures registered in various parts of the oven?

Many thanks in advance,

W.
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Old 10-30-2007, 12:59 PM
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Default Re: Thermocouples: what kind?

See these threads, they should answer your question. If not then please ask again.

http://www.fornobravo.com/forum/f28/...t=thermocouple (Thermocouples -- what to do?)

http://www.fornobravo.com/forum/6/th...t=thermocouple (Thermocouple Queries)

I would not purchase the thermocouples you alluded to. Not the correct type and can get new ones cheaper.
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Old 10-30-2007, 02:25 PM
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Default Re: Thermocouples: what kind?

Thanks Wade, from these posts I have worked out the positions for the thermocouples. I am still not clear whether they need some sort of tube around them and what are the temperature ranges.

I guess I'll go with the glass bead Omega ones with 2m wires. And if I find some teflon tube lying around, I'll use that to shield the business ends. They should work up to 450 deg C, which judging from what I have seen here should do inside the bricks and further out. Will someone correct me if I am wrong?

I'll try to get them in for the floor at an early stage (before pouring the support slab). Incorporating some into the dome should be easier. I am tempted not to drill the dome but to squeeze the probes between the elements/bricks.

Is this a good plan?

Cheers,
W.
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Old 10-30-2007, 06:12 PM
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Default Re: Thermocouples: what kind?

W.

I wouldn't use teflon to sheath the thermocouple as it is not a good conductor and I would not teflon at high temp anywhere near food. If you want it sheathed then go with stainless.

Since I have been using my oven I have rethought the need for sheathing. TC's are great for getting to learn the temp performance of your oven, but unless you are into alot of extended time baking the need for them wanes. So, if you get 3 years out of an unprotected one then that would be plenty. Just my observations, your or others needs/uses may be different.
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Last edited by wlively; 10-30-2007 at 06:40 PM.
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Old 10-31-2007, 02:43 AM
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Default Re: Thermocouples: what kind?

Thanks - so teflon is out for food safety reasons (but how about the teflon pots and pans?).

With stainless steel - does the thermocouple need some electrical insulator?

And finally, I had exactly the same thoughts re. the learning curve and the ned for continuous measurements - thanks.

Best wishes,

W.
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Old 10-31-2007, 04:18 AM
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Default Re: Thermocouples: what kind?

Yes teflon is on pots and pans, but it starts to give off fumes above 400+deg F and can give you flu like symptoms, "teflon flu" they call it. Teflon tubing is formulated a bit different and we use it at work for exhaust lines on 800 deg C furnaces, that are cabinet exhausted. What fumes are given off by teflon at that temp? Who knows. When teflon burns it breaks down into highly toxic components, another reason to avoid.

When you buy a stainless sheathed TC it comes that way from the manuf so the electrical isolation is taken care of, so you are right you would not want to placed an exposed tip TC into a home made stainless tube. So either buy the integrated stainless TC's or the reg exposed tip glass or ceramic.

Happy building.
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