8.0 Repairs and Replacements
Adjustment
After any thyristor unit replacement, or any change of voltage or
transformer tapping, the potentiometer on the thyristor must be
adjusted to give the correct element current. This should be done by a
qualified person, as there are dangerous voltages inside the control
compartment. It also requires a calibrated non-intrusive clip-on
ammeter.
Before connecting the electrical supply, turn the potentiometer on the
thyristor fully to the left (anti-clockwise). This sets the output current of
the thyristor to 'off'.
Connect the electrical supply with the side cover off. TAKE CARE! Set the furnace
temperature to maximum. Allow the furnace to start heating up.
Measure the current through the element circuit. This is carried out with the clip-on
meter around one pair of thick cables on the left-hand side of the transformer (as seen
when facing the control side of the furnace).
Adjust the potentiometer on the face of the thyristor unit. Adjust it slowly to the right
(clockwise) to increase the current, pausing to allow the time for response at the meter.
Keep adjusting to obtain an ammeter reading of between 149 to 150 A for the HTF 1700
or 139 to 140 A for theHTF 1800. This adjustment should be set up within the first 5
minutes of heat up from ambient and should finally be checked when the furnace
temperature is approximately 100 °C below its maximum temperature. Make further
adjustments if necessary at this temperature.
Disconnect the electrical supply to ensure safe replacement of the side panel. See
section 8.1
8.7
Fuse Replacement
Fuses are marked on the wiring diagram with type codes, e.g. F1, F2. For more
information on fuses refer to section 11.0.
Depending on model and voltage, the different fuse types may or may not be fitted.
If any fuse has failed, it is advisable for an electrician to check the internal circuits.
Replace any failed fuses with the correct type. For safety reasons do not fit larger
capacity fuses without first consulting Carbolite Gero.
The fuses are located at the cable entry point. Remove the back panel or control box
back panel to gain access to the fuses.
8.8
Thermocouple Replacement
Disconnect the product from the electrical supply and remove the product's element
access panel.
Make a note of the thermocouple connections. The negative leg of the thermocouple
is marked blue. The "compensating" cable for 1700 & 1800 °C thermocouples is plain
copper.
52
Summary of Contents for CARBOLITE GERO HTF 18/15
Page 36: ...4 0 3508 Dual Loop Cascade Power Limit View 36 ...
Page 55: ...Element Connections 1 phase Element Connections 3 phase 55 8 0 Repairs and Replacements ...
Page 58: ...10 0 Wiring Diagrams 10 0 Wiring Diagrams 10 1 239 4 5001 58 ...
Page 61: ...Notes Service Record Engineer Name Date Record of Work ...
