For silicon carbide heated furnaces the parameter is accessible to allow for
compensation for element ageing. In wire-heated chamber or tube furnaces, reducing
the power limit is a convenient method of improving control at low temperatures, as
outlined below.
The power limit may be set to zero to permit demonstration of the controls without
heating.
In many models the power limit setting depends on the supply voltage; usually the
furnace or oven manual contains details: if in doubt, contact Carbolite Gero for advice.
The power limit parameter does not apply to the over-temperature controller, if fitted.
Altering the value
Press page
until oP (output list) is displayed. Press scroll
until OP.Hi (Output High)
is displayed. Press down
or up
once to display the value of OP.Hi and write down
the value. To alter the value, use down
or up
.
Note: setting the value to zero prevents the furnace or oven from heating.
Caution: Do not increase the power limit value to a value above the
design level for the oven or furnace model, or to a value above that
correctly calculated for silicon carbide elements. The heating elements
could burn out, or other damage could be caused.
Control at Low Temperatures
If a product is to be used at temperatures much lower than its design maximum,
control stability can often be improved by reducing the power limit. Remember to make
a record of the original setting before altering the power limit.
Example: It is desired to operate a 1200 °C furnace at 300 °C. The normal control
settings can be expected to cause excessive overshoot as the furnace reaches
temperature. If the power limit OP.Hi is normally set to 100%, try a setting of 40%.
This should greatly reduce the overshoot. (There is no firm calculation rule to get this
example setting of 40% – experimentation may be required to achieve a good result.
Avoid power limits below approximately 30% – control accuracy is reduced at such
levels.)
Depending on the furnace or oven model the power limit parameter OP.Hi (Output
High) may be accessible or hidden.
For silicon carbide heated furnaces the parameter is accessible to allow for
compensation for element ageing. In wire-heated chamber or tube furnaces, reducing
the power limit is a convenient method of improving control at low temperatures, as
outlined above.
The power limit may be set to zero to permit demonstration of the controls without
heating.
In many models the power limit setting depends on the supply voltage; usually the
furnace or oven manual contains details: if in doubt, contact Carbolite Gero for advice.
User Calibration
47
4.0 2132 Controller
