The programmer is used in conjunction with a phase angle thyristor power controller,
which incorporates a current limit potentiometer pre-set by Carbolite Gero, but which
will require adjustment in the event of change of supply voltage.
The elements are connected in series across the low voltage output of a transformer
housed in the furnace case. Molybdenum disilicide elements do not age, if an element
fails it is not necessary to replace the complete set.
6.10
Thermocouple Warnings
(1) The output from 1700-1800 °C thermocouples when used regularly at temperatures
greater than 1650 °C can deteriorate and decrease with age faster than if used at
temperatures below 1650 °C; this will cause the furnace to operate at temperatures
higher than indicated.
Operators are advised to periodically check the thermocouple output, either by a
calibration test or by comparing the output with a new reference thermocouple which
has been subjected to high temperatures for a minimum length of time.
Failure to check the thermocouple regularly may result in overheating of the work and
the furnace, with consequential damage to both.
(2) The thermocouples fitted to these models give very low outputs below
approximately 600 °C and do not give accurate readings at low temperatures. They
may show a negative temperature when the furnace is started from cold.
This furnace is not intended to operate with a setpoint below 600 °C.
6.11
Thermal Cutouts
There is a thermal cutout on the interior case surface at the centre top near the
chimney. In the event of fan failure or any other reason for case over heating, power to
the heating elements is cut.
To reset the thermal cutout, first isolate the furnace from the electrical
supply. Remove the top panel and press upwards the button on the
cutout device. TAKE CARE - the chimney may be hot.
There is a further thermal cutout in the element circuit transformer
which cuts power if the transformer core overheats. This is self-
resetting.
If either thermal cutout is activated, then a fault light on the control
panel is illuminated.
45
6.0 Operation
Summary of Contents for CARBOLITE GERO HTF 18/4
Page 7: ...Caution Double Pole Neutral Fusing 7 1 0 Symbols and Warnings ...
Page 37: ...Power Limit View 37 4 0 3508 Dual Loop Cascade ...
Page 59: ...59 8 0 Repairs and Replacements ...
Page 63: ...GR Y Green Yellow 63 10 0 Wiring Diagrams ...
Page 67: ...Notes Service Record Engineer Name Date Record of Work ...
