HRF
8
MF05
5.5
Thermocouple Replacement
Disconnect the furnace from the supply, and remove the furnace back panel.
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.
Re-assemble with a new thermocouple observing the colour coding, ensuring that the any
porcelain spacers are replaced.
5.6 Element Replacement
See section 5.2 - wearing a face mask is recommended.
The mineral insulated type of element consists of a resistance wire which is centred in a metal
tube by a compressed powder.
Such elements may be bent into "U" or other shapes without losing
the electrical insulation.
Disconnect the furnace from the supply.
Remove the furnace back panel.
Carefully note how the elements are connected, and remove the electrical leads from them.
Unscrew the gland caps on the faulty element, and carefully prise open the split compression
collars, which should be retained for fitting to the new element.
Remove the chimney, open the furnace door and slide out the chamber liner.
Withdraw the element through the front of the furnace.
Insert the new element through the glands and refit the compression collars.
Their centres should
be approximately 40 mm from the end of the element.
Firmly tighten the gland cap, ensuring the
element lies centrally between the chamber liner and the insulation.
Reconnect the electrical leads, refit the chamber liner and back panel, and reconnect the supply.
Check that the furnace is controlling properly to rule out the possibility that previous element
failed because of a fault elsewhere in the control circuit.
Note on 208V elements: these elements are marked “240V 2000W”. These elements correctly give
1500W when used at 208V.
5.7
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.
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.
6.0
