9.0 Repairs and Replacements
9.4
Solid-state Relay Replacement
Disconnect the product from the power supply and remove the
appropriate cover as given above.
Make a note of the wire connections to the solid state relay and disconnect them.
Remove the solid state relay from the base panel or aluminium plate.
Replace and reconnect the solid state relay ensuring that the bottom of it has good
thermal contact with the base panel or aluminium plate.
Replace the access panel.
9.5
Thermocouple Replacement
The coverings and guards which must be removed to gain access to the thermocouple
depend on the model, its orientation (horizontal or vertical), and possibly other options
and fittings.
It will usually be necessary to separate the product from its base or stand. On horizontal
models one outer end-cap will need to be removed and on vertical models the terminal
cover. Within some models the thermocouple lies inside the product body; the body
must be removed from the control base and the end-cap and insulation ring removed
from one end.
Disconnect the product from the power supply. Remove terminal cover to gain
access to the thermocouple connections. Make a note of the thermocouple
connections.
Thermocouple cable colour codings are:
thermocouple leg
colour
positive (type K)
green
negative
white
Disconnect the thermocouple from its terminal block. Withdraw the thermocouple from
its sheath and remove any broken bits of thermocouple.
Bend the new thermocouple carefully to match the shape of the original (working from
the terminal end). Should the length differ from that of the original this will usually not
be important provided that the thermocouple tip is within a tube diameter's distance
from the product centre.
Insert the new thermocouple into position, restoring any removed porcelain spacers and
ensuring correct polarity. Re-assemble the product.
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