7.6
Element Replacement - 1200 °C Models
See section 7.2 - wearing a face mask is required.
The chamber of this type of furnace contains a tubular refractory muffle around which is
wound resistance heating wire. In the event of failure, the whole "wound muffle"
assembly must be replaced.
Disconnect the product from the electrical supply and remove both product end panels.
Make a note of all the wiring connections; see section above which refers to the
thermocouple colour coding.
Unfasten the electrical connections to the inner chamber (brick-box) and remove the
thermocouple (see thermocouple replacement instructions). If the connections are
secured by hexagonal nuts, two spanners should be used to avoid cracking the porcelain
mounting.
Undo any screws, bolts or hook bolts necessary to release the brick-box.
Support the brick box as you withdraw it from the case so it does not fall onto the
electrical connections below.
Remove the brick box lid and all insulation, noting how it is assembled and observing
the position of the heating element wires (or "tails").
Pull the element tails out of the terminal blocks and remove sufficient insulation to allow
access to the heating element. Check and replace damaged insulation.
Fit the new heating element, ensuring that the tails are separated from the element by
at least 25 mm of insulation.
Feed the heating element tails through the terminal blocks and tighten the clamping
screws using two spanners as before. Cut off excess element tails.
Refit the insulation and refit the lid. Do not use any cement unless supplied by Carbolite
Gero, as other types may chemically attack the heating element.
Replace and fasten the brick-box into the products case.
Replace the thermocouple and remake the electrical connections. In porcelain and
brass terminal blocks the brass connector should be slightly loose in its porcelain
support block to allow for expansion.
Replace the panels and reconnect the electrical supply.
Switch the product ON and heat to 900 °C without interruption and then dwell for 1
hour. Some smoke may be observed during this process, which should be carried out in
a well ventilated area.
Check that the product is controlling properly to rule out the possibility that previous
element failed because of a fault in the control circuit.
If you have any problems with this procedure, please contact the Carbolite Gero service
division.
31
7.0 Repairs and Replacements
