This is a question we hear all the time. As one looks for an oven to meet their production needs, there are often many questions as to which is the “right” oven to purchase. Differences in design can have an impact on the quality and quantity of product that you can produce. There are three basic types of gas/oil fired, stone hearth deck ovens. While they may appear similar from the outside, each has its own baking characteristics and advantages. The major differences are how the heat is distributed to the decks, the type of materials that are used in the construction, and how they generate their steam for the baking process.

I. CICLOTHERMIC:
Cyclothermic ovens circulate hot air between and around the decks either indirectly through a heat exchanger or directly from the burner. Other than the baking surface, these ovens are typically all steel construction with mineral wool type insulation. The advantage of the cyclothermic is the ability to change temperatures rapidly. Some also have the ability to regulate the temperature on the top 1 or 2 decks to a lower temperature than the bottom decks to accommodate various products at the same time. Because air does not hold heat very well, it is not considered to be a very efficient means of heating.

Cyclothermic ovens are not usually recommended for baking 'heavy' products. As with a hot air heating system in a home, when the burner shuts off, there is a tendency for the oven to cool down rapidly until the thermostat calls for more heat. Then when the burner re-ignites or goes back to high flame, the temperature will rise again quickly. This produces more oven temperature fluctuation than might ideally be desired for baking breads with longer bake times, especially if you are using steam and desire a good thick crust. The oven will also be limited in the amount of production due to the time required to recover from the heat loss.

II. VAPOR TUBE
Vapor Tube ovens circulate heat through the use of a series of sealed, thick wall tubes that contain approximately 1 liter of water. Each tube surrounds the oven chamber and as well as passing above and below the decks. The bottom portion of each tube rests directly on the burner chamber. The water inside the tube quickly boils, turning to steam. By natural thermodynamics, the steam circulates through the pipes, radiating its heat through the oven walls and stone hearth. As the heat is transferred, the steam returns to the liquid state and returns to the bottom of the tube, where the entire process begins again. The heating system requires no moving parts or fans to distribute the heat, thereby eliminating a potential source of uneven baking and required adjustment and maintenance. Vapor tube ovens also provide excellent baking quality since the tubes themselves serve as an excellent thermal mass. Two versions of vapor tube construction are:

    • All Steel construction models: For many years, most of the vapor tube ovens installed in the U.S. were of all steel construction and performed well in many situations. As demand for hearth breads has increased, however, many bakeries find that an all-steel oven cannot maintain the heat necessary for this type of baking and steaming. This can result in a greater degree of change in baking properties or unevenness of baking after 6 hours or so of heavy production. The recovery of the steam system can also be adversely effected by the lack of heat retention.
  • Steel and Cement Construction: Many European bakeries have long used a combination of steel, cement and brick to achieve the same baking properties as a brick oven. In essence the brick and cement act as a “heat sink”. In this way, when the oven is loaded with bread, and steam is introduced into the chamber thereby absorbing the chamber's available heat, the brick and cement supply a continuous, smooth flow of heat without the burner having to try and play “catch up".Some ovens utilize brick in the fire chamber while using mineral wool or other insulation in the walls. These are usually considered superior to the “all steel” and cyclothermic ovens for the production of most hearth breads requiring good properties of heat retention and repetitive steam cycles.

    For the ultimate in “brick oven baking”, ovens are available with cement-lined walls and roof panels. Filling the walls and roof panels with cement (and thereby surrounding the entire baking chamber with thermal mass) retains the greatest amount of heat and is preferable for baking large or heavy breads and for heavy production schedules.

    Steel ovens without the cement do not have the ability to store nearly as much heat and therefore are much more dependent on the burner to immediately supply the heat needed. This gives a very different baking characteristic than the traditional brick oven. Most bakers, who have used both styles of vapor tube oven and wish to closely simulate an actual brick oven, prefer the cement and brick design. Of course it is easiest to move an oven without any cement at all and one needs to weigh the importance of this in choosing the proper oven type.

III. THERMOIL
Thermoil Ovens generate their heat in a heat exchanger, outside of the oven, by heating a special oil composition in an oil heater or “boiler” (although not actually a boiler since the oil does not boil). This heated oil is then pumped through radiators inside the oven decks, radiating the heat for the baking process. While certainly the most expensive deck oven to purchase, there are several advantages to this style of oven. Because fluid is being pumped through radiators the flow can be controlled for adjustment of heat in various zones of the bake chamber. In addition, ovens of greater capacity than cyclothermic ovens can be built. The fluid is also an excellent conductor of heart, providing a high level of energy efficiency. Also because the burner is remote from the oven, it can be located in a clean area of the bakery and produces no noise in the bake room.

GENERATING OF BAKING STEAM
Deck ovens usually generate the steam for the baking chamber from the same heat source as the baking heat …the burner. The major difference in deck ovens will be, where the steam generating units are located and their ability to produce consistent steam in rapid cycles to accommodate the constant loading of the oven in high production situations. The best application is to have heavy duty steel boxes filled a heat retaining material, such as construction grade steel bars (rebar) directly in the hottest part of the heat production system. In a vapor tube oven this will be under the bottom deck. As an alternative, some manufacturers place troughs on the side of each deck, but it is generally thought that in mid to large size ovens this is not as effective and does not have the ability to “recover” quickly enough bake after bake. In any system, it is important that the steam system be accessible for cleaning and occasional decalcifying, if necessary.

Let us help find the right Deck Oven for you!
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