Carbolite RHF Series 3 litre - 35 litre - Manual (Page 9)

RHF
MF07 – 3.10
9
5.5 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.
5.6 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: white positive (type R): orange
Disconnect the thermocouple from its terminal block.
Bend the metal tag, or release the screw, to release the thermocouple sheath; withdraw the sheath,
and shake out any fragments of thermocouple.
Re-assemble with a new thermocouple observing the colour coding, ensuring that the
thermocouple is not twisted as it is being inserted and that sheath is refastened.
5.7 Element Fitting and Replacement
Replacements: read the section on element ageing (4.5). If at any time the power limit has been
increased, reset it to its original value (section 8.2), or measure the resistances and recalculate
the limit.
Disconnect the furnace from the electrical supply and remove the furnace back panel to gain access
to the element connections.
Remember that the elements are fragile and expensive, and that they can be damaged by
contamination: handle them with care and keep them clean.
Replacements: make a note of the actual braid and cable connections to the elements. Disconnect
the braids or cables and carefully withdraw each element.
New furnace: the diagrams indicate the connections, but the number and positions of terminal
blocks may differ from those shown. For example, there may be 3 x N on a 3-phase furnace. If you
have any problems with this procedure, please contact our service division. A common feature of
all the RHF models is that elements are always 2 in series between 200-240 volts (for 110V, 2 in
parallel).
Carefully insert the new elements into the furnace. Position elements so that the split along the
length is vertical.
Attach the braids according to the notes made, or according to the appropriate diagram below
Replace the furnace back panel and connect the furnace to the supply.
If aged elements have been replaced, reset the furnace power limit.