THEORY OF OPERATION LBB Series Oven Owner’s Manual
20 Version 13
Copyright © 2011 by Despatch Industries.
All rights reserved. No part of the contents of this manual may be reproduced, copied or transmitted in any form or by any
means including graphic, electronic, or mechanical methods or photocopying, recording, or information storage and
retrieval systems without the written permission of Despatch Industries, unless for purchaser's personal use.
3.1.1. Oven Theory
The LBB Series forced circulating oven uses fan to circulate air through the chamber. A
circulating oven is much more efficient and uniform oven than a gravity-convection oven
due to the constant air movement. Soaking at a desired setpoint still depends on a number
of parameters including chamber area, load mass, the ability to absorb heat and the
exhaust rate. But soak times with a forced circulating oven may be shortened.
The LBB Series Oven is capable of heating to 204°C (400°F). The oven uses a
microprocessor-based digital control to display the actual chamber temperature at the
sensing point. The temperature sensor is located to optimize control action for the entire
chamber for various load conditions. While the control display may fluctuate a few
degrees around the setpoint, reflecting temperature changes at the sensor location.
However, overall chamber temperature remains stable. The strategic location of the
sensor compensates for delays in heat convection and enhances the performance and
temperature control of the oven. The oven has been designed for an overall result of
quality productivity where fast processing and versatility are critical.
3.2. Control Systems
3.2.1. Primary Control Instrument
The LBB Series Oven is equipped with a microprocessor-based digital control instrument
configured as a proportional controller and set to its optimum operating values (Figure 3).
Initially the control instrument allows the heater to operate at full power. As the actual
oven temperature reaches the setpoint, the control instrument cycles the heater on and off,
minimizing process temperature fluctuations. Table 1 provides explanation for working
with the control instrument.
Warning!
Do not remove the hat bracket as it distributes exhaust air and
protects the exhaust opening from being completely covered.
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