Carbolite HTMA Series - Manual (Page 10)

High Temperature Ovens
10
MF16 3.09
5.5 Solid-state Relay Replacement
Remove the control panel as given above. Make a note how the wires are connected to the solid
state relay, and disconnect them.
Remove the solid state relay from the aluminium plate.
Replace and reconnect the solid state relay ensuring that the heat-conducting thermal pad is
sandwiched between the relay and the base panel or aluminium plate. Alternatively a thin layer of
white, heat-conducting silicon paste may be applied between the new relay and the plate.
The new solid state relay contains a built-in MOV which protects it from short periods of excess
voltage. If the old relay had a separate disc-shaped "MOV" connected between the high voltage
terminals of the old relay, discard the old MOV.
Replace the removed panel.
5.6 Thermocouple Replacement
Remove the control panel and the internal cover as given above.
Make a note of the thermocouple connections, and how the thermocouple is placed and fixed.
Colour codings are:
negative positive (type K)
white green
Disconnect the thermocouple from its controller terminals or terminal block.
Re-assemble with the new thermocouple observing the colour coding.
5.7 Element Replacement
Remove the control panel and the internal cover as given above. LHT: the element terminals are
low down in the side compartment. HT: the element terminals are accessed from the back.
Disconnect the wires from the element terminals. Remove any starlock washers - these may need
to be cut with wire cutters. Remove any clips holding the element inside the chamber, and
withdraw the element.
Reverse the procedure with the new element.
Run the oven at a low temperature and check that it is controlling properly, to find out whether the
element failure was caused by a fault in the control circuit.