Instruction Manual

LAC Series Oven Owner’s Manual THEORY OF OPERATION
Version 1 19
Copyright © 2012 by Despatch Industries.
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3.2. Damper Control
The LAC-7 oven is equipped with a manually-adjustable damper mechanism. The damper control
arm is located on the front panel of the oven (Figure 1). The damper adjustment controls the
fresh air opening which, due to pressurization of the oven chamber, controls the flow of exhaust.
If the damper is in the full open position, the maximum exhaust rate is achieved. If the damper is
in the fully closed position, the minimum exhaust rate is achieved.
3.2.1. Determining Damper Settings
The optimum setting for the damper depends on a variety of
factors. These factors include ambient environment temperature,
load conditions, load distribution, heat-up and cool-down rates,
desired temperature uniformity and most importantly the desired
operating temperature. Additionally, engineering tradeoffs for
each factor must be carefully weighed. While considering each
factor independently may be too daunting, guidelines provide a
simpler way to determine damper settings.
In general, set the damper so the amount of fresh air flowing into
and exhausting from the chamber agrees with the desired operating
temperature conditions. The following outline provides practical
considerations for various damper position settings (Figure 3).
3.2.1.1. Damper Full Closed Position
The damper in full closed position allows maximum attainable
heat-up rates for the chamber. In addition, the chamber uses minimum
power to operate at the desired temperature. In most cases, maintain the damper in the full closed
position to efficiently operate at the maximum operating temperature for the chamber.
3.2.1.2. Damper Full Open Position
The damper in full open position allows minimum operating temperature for the chamber.
Friction heat from the air recirculation system builds up in the chamber. This causes chamber
temperature to rise slightly though the heating system is not ON. After the recirculation motor
has been ON for an extended period of time, the chamber reaches a thermal equilibrium
temperature.
When the damper is not set to full open position, the chamber has no way to readily dissipate the
heat generated by the friction. With the damper fully open, the thermal equilibrium temperature is
the minimum operating temperature of the chamber.
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When the damper is in the full open position, the oven may not
be able to heat to the maximum oven operating temperature.
Figure 4. Damper Positions.