Turning up the heat
It’s time to fill that insulated, optimized baking chamber with heat. “It is critical to understand [the burners’] role in the process and have a control system that can monitor and operate them efficiently,” said Scott McCally, vice-president of engineering, Middleby Bakery Group.
Burners have an impact on the energy efficiency of the oven, including burner design, deployment and operating strategy. It’s a common misconception that all the burners in an oven must be lit at all times because it wastes energy and may lead to an inconsistent bake. “The strategic locations where burners are turned on should be programmed based on each individual product’s baking profile, or S-curve,” Mr. McCally said. “Burner programming by product does require professional expertise and instrumentation; however, it is critical to the efficient operation of the oven.”
Burners running at low fire can also be a challenge. “It’s important that an oven’s control system is always modulating and that the only time an oven goes to low fire for any measurable duration is when it is empty,” Mr. McCally said. “A modulating oven is one that is in control and presumably moving heat into zones that demand it based on load. An oven that has product inside and is in a low fire state is out of control and wasting heat.”
High-efficiency burners can handle these low levels. J4’s Weishaupt burners can turn down to a very low burner level and not turn off. “You can go down low and come back up smoothly and gently,” Mr. Morabito said. “They’re very efficient, especially from an emissions standpoint with a low carbon output.”
In a thermal oil system, oil is pumped to radiators in the oven located above and below oven belt or deck. Thermal oil systems can also bake using convection and conduction as adjuncts to their primary means of baking, which is radiation. Thermal oil aids in baking efficiency by conducting the heat into the chamber. “Thermal oil holds something like 2,300 to 2,500 times the energy in 1 cubic cm as air,” said Stephen Bloom, vice-president, Allied Bakery Equipment, which represents the Heuft brand in the US. “The net result is you heat up this thermal oil, and it holds its heat. It’s like baking in a brick oven.” Because of this ability, the oven temperature does not have to be set higher than necessary to get the correct bake.
With this kind of control, the oven can impart a precise baking profile. “You get a consistent bake because thermal oil is a liquid medium, and the energy is so well-controlled that anywhere on the baking deck, the temperature doesn’t vary more than 2°F, so you get consistency with bake without any hot spots,” Mr. Bloom said.
Learn how to best use air in the oven in the next section.
