Carbolite HTR 11/150, Installation, Operation & Maintenance Instructions Manual, Page: 9 / 16

HTR
MF30 – 3.07
9
5.5 Thermocouple Replacement
Disconnect the furnace from the supply, and remove the back panel. The thermocouple and its
sheath are on the exhaust (right-hand) side.
Make a note of the thermocouple connections. The negative leg of the thermocouple is marked
blue. Compensating cable colour codings are:
negative positive (type K)
white green
Disconnect the thermocouple from its terminal block.
Withdraw the thermocouple from its sheath and remove any broken bits of thermocouple.
Insert the new thermocouple into position, restoring any removed porcelain spacers, and ensuring
correct polarity.
Re-assemble the furnace.
5.6 Element Replacement
See section 5.2 - wearing a face mask is recommended.
The element is supplied complete with the surrounding stainless steel half-cylindrical inner
chamber.
Disconnect the furnace from the electrical supply, and remove the back panel. Work with the
furnace lid open, with no vessel in place.
Make a careful note of the colours and positions of all the electrical connections to the inner
cylindrical chamber and thermocouple.
Disconnect the thermocouple and element connections from their terminal blocks.
Remove the thermocouple. It may also be necessary to remove the thermocouple sheath: loosen
the retaining screw and withdraw the sheath.
Supporting the weight of the inner chamber, loosen 4 screws holding brackets to the top plate;
loosen and remove 4 screws holding the chamber to the brackets.
Lift out the inner chamber.
Fit the new chamber by reversing the process. Take care to make all connections to the correct
terminals. Do not overtighten the connectors in porcelain terminal blocks.
Let the furnace heat up at its maximum rate to 900°C without interruption, and then soak for 1
hour. Fumes may be emitted: this should be done in conditions of good ventilation.
Check that the furnace is controlling properly to rule out the possibility that the element failed
because of a fault in the control system.
If you have any problems with this procedure, please contact our service division.