5.0 Operation
5.3
Operator Safety
The ceramic materials used in the product manufacture become
electrically conductive to some extent at high temperatures. DO NOT use
any conductive tools within the product without isolating it. If a metal
work tube is used, it must be earthed (grounded).
Switch off the heater switch whenever loading or unloading the product.
The elements are isolated when the heater switch is OFF. This switch
cuts both sides of the circuit via a contactor.
5.4
Tube Life
A ceramic work tube may crack if work pieces are inserted too quickly or at
temperatures below 900 °C (when the tube is more brittle). Large work pieces
should also be heated slowly to ensure that large temperature differences do not
arise.
Poor thermal contact should be encouraged between the work piece and the tube;
crucibles or boats should be of low thermal mass and should have feet to reduce the
contact with the tube (fig. 4).
Key
A
Tube
B Crucible
Fig 4 - Avoidance of thermal contact
Do not set too high a heating or cooling rate.
5.5
Power Adjustment
The product control system incorporates electronic power limiting. The power limit
parameter OP.Hi is accessible to the operator and can be used to adjust the product to
the actual supply voltage.
Some models covered by this manual are fitted with 208 V elements and are designed
for use over the range of voltages 200 V- 250 V; the power limit parameter is set
accordingly. These models may be relocated to a different voltage within the range: the
power limit should be reset to match the voltage.
To check whether the furnace is a 208 V model:
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