Heatrae Sadia SUPREME Fitting Instructions And User Manual page 12

9.5 Scale deposits should be removed from all internal surfaces,
particularly the heating element, thermistor, and level sensors by
gently tapping or scraping. If the deposits are soft, use a nylon
pad and flush out. Abrasive cleaning materials containing scouring
powders and detergents must not be used, as such materials can
cause taste problems.
9.6 Suitable chemical de-scalants must only be used in accordance with
the manufacturers recommendations. This will prevent health and
safety issues, taste problems, and potential damage to the appliance.
All trace of these chemicals must be removed from the appliance
before re-commissioning the unit . Misuse of such chemicals is not
covered by the product warranty.
IMPORTANT Before re-commissioning the unit, it is important that all
scale and moisture is removed from the level sensor insulating
gaskets to avoid a false signal being transmitted through the scale
to the unit body. Failure to remove this scale and/or moisture could
cause the sensor to indicate to the PCB that water is covering the
element, whether or not water is present. In this situation the PCB
could energise the element causing failure. If in doubt, protect the
element by hand filling with water to the level of the draw-off tap
before switching on the electrical supply to the unit.
9.7 General function
The printed circuit board (PCB) controls the heating and filling
functions of the unit by monitoring the thermistor and level sensors.
The PCB also controls the external light unit to indicate the current
state of the appliance. Red and yellow LED'S on the circuit board
indicate whether the PCB has energised the element or solenoid
respectively.
Should an element fail and need to be replaced, it may be necessary
to replace the lid gasket to ensure a steam-tight joint. Note: the
element has a permanent 'Live' feed, and the 'Neutral' is switched.
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