Thermocouples

Sheryl

We are making a brick bread oven , also wood-fired. Do we realy need to install thermocouples, what benefits has anyone had? If we do, where can we buy them from in New Zealand? What about using a stainless steel thermometer that is placed in the oven as required?
Many thanks if someone has some answers.

Replies

Graham's picture
Graham 2008 December 10
It is preferable to have an indication of temperature while you are firing the oven. This will help you to more accurately assess when to stop firing the oven. This is even more important if you are likely to switch wood varieties which burn at different temperatures.

Perhaps there is a mobile thermometer that could achieve this task ...temperatures during firing go very high...however the mobile thermometer may not be capable of providing a deeper level of temperature assessment, an indication absorbed heat in the fire bricks (rather than just surface heat). Firing an oven correctly is all about assessing that a satisfactory amount of retained heat has been achieved.

My experience is in side-flu Scotch ovens. Traditionally they used a thermometer which was exposed to the main chamber of the oven during firing, though on the opposite side to the fire and protected somewhat by a metal pipe housing. Alan Scott places several thermocouple thermometers during installations for his ovens. I will ask him for his opinion and report back.

Thinking aloud now...but I think that your idea of a stainless thermometer, during firing, might work if you house it in metal pipe / or a shield and attune yourself to how the subsequent readings indicate retained heat potential of your oven.
jacklang 2008 December 10


Different thermometers measure different things. I find I need hem all.
You need thermocouples or an embedded thermometer to measure the temperature in the brick, which represents the amount of heat stored. An oven thermometer measures the air temperature, and a laser thermometer measures the surface temperature of the brick. The surface temperature can vary quite quickly, for example if exposed to the fire or if cooled by opening the door or having cold dough in contact.

Ideally you need several thermocouples embedded in different places and different depths to give you a full picture. Thermocouples don' last forever so you need to embed them so that they both have good thermal contact and can be replaced, for example inside narrow bore conduit or copper pipe drilled into the brick and under the hearth from outside.

You might want to look at http://groups.yahoo.com/group/brick-oven where there is an active debate about thermocouples at the moment.
Graham's picture
Graham 2008 December 11
Jack, if you could only have one thermocouple thermometer, where would it be located? Which one is the most useful?
jacklang 2008 December 11
Middle of the hearth, under the hearth tiles - about an inch under the surface of the hearth
Alternatively middle of the dome, also about an inch in.

Eventually you experience and feel will guide you, but thermocouples are still useful, and cheap.
gavinc 2008 December 17
I put two thermocouples in my backyard brick oven.  One in the dome and one in the floor.  I drilled into the brick to within 5 cm of the inner surface and cemented a "K" type thermocouple.  I have some pictures on flickr if you want to seen how I build my oven.  This link is to the picure of the thermocouple after I installed it into the brick dome.  http://www.flickr.com/photos/27771627@N07/2589137933/

You could order them from Pyrosales and have them mailed over to NZ.

Cheers,
Gavin (Rosebud Australia).
Sheryl 2008 December 20
Many thanks for your advice, which i have taken on board. Purchased a K-type thermocouple from a firm in NZ selling electrical and engineering stuff called JA Russell. I got mine in  Pukekohe but they appear to be everywhere. I did have to order it in and it came from Australia. My cost was $82 and that was the cheapest one available on the market here. Thrilled too have it too, 'cause once I can start baking I dont want to cook "Cordon Noir" Loaves.
We plan to instal it under the floor and have drilled a hole to insert in to the concrete. We salvaged a short piece of stainless steel tubing from my Dad's old dairy, which he was using for a garden stake and that wil be our conduit in case we need to replace the thermocouple in the future.
This weekend we are doing the hearth floor and hope to make a Xmas holiday project with our family all involved doing the oven part. I am hoping to light a small fire then and be able to perhaps bake some lavosh bread. Cheers Sheryl
Pemmican man 2019 May 17

Im looking for advice on what thermocouple to purchase for a wood fired oven im building any help, im in canada

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