Carbolite GPC Series - Manual (Page 10)

GPC
10
MF04 3.29
Disconnect the furnace from the electrical supply and remove the back panel.
It is advisable to make a written plan showing all the element and thermocouple connections to
avoid any problems when reconnecting to the power and other wires.
Loosen the clamping screws onto the terminal blocks holding the faulty element. Use two spanners
to avoid cracking the porcelain material. If necessary straighten the bent ends of the wire. This
must be done for both ends of the element, i.e. for two adjacent terminal blocks.
Withdraw the tube on which the wire spiral is mounted, through the back. The second person
should assist by supporting the tube within the chamber and easing the element off it.
From within the chamber, lift the wire element off the hook holding the front end, and remove the
element through the furnace door.
Fit the new element. At the same time one person should feed the tubes through from the back, and
the other should feed the wire spirals onto the tube.
To get the wire ends through correctly it may help to feed a flexible plastic or nylon tube, with a
bore just larger than the element wire, through the terminal block into the chamber. Fit the element
wire into this tube; as the tube is withdrawn, the element feeds through the terminal block.
Finally locate the element correctly. At the front, connect the hook. At the back, ensure that the
last turn of the spiral is approximately one turn away from the insulation. Then tighten the terminal
block screws.
If necessary, cut off any excess wire.
Refit the back panel.
Check that the furnace is controlling properly to rule out the possibility that the previous element
failed because of a fault elsewhere in the control circuit.
5.8 Fuse Replacement
Fuses are marked on the circuit diagram (section 7.0) with type codes, e.g. F1, F2. A list of the
correct fuses is given in section 8.1. 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.
The fuses are near the cable entry point, and access is by removal of the back panel.
5.9 Door Plug Replacement (Laboratory models)
See section 5.2 - wearing a face mask is recommended.
The door insulation is made of bonded refractory sections, supplied as one piece.
Lift the furnace door to the open position and remove the door cover from the plug carrier
assembly by loosening the nuts at each side.
From the front, unscrew the self-tapping screws which hold the upper door plug retention bracket
in place, and remove the bracket.
Remove the old door plug.
Place the new door plug in position, ensuring that the chamfered edge is uppermost.
Refit the upper bracket and door cover.
When first heating the furnace after a replacement, ensure that the ventilation is good: emission of
some fumes may be expected.