Heating - Fisher & Paykel DishDrawer DD247 Service Manual

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3.8 Heating

3.8.1 The Heating Element
The heating element is a porcelain enamelled steel plate, with
a thick film resistive coating circuit printed onto the dry side. A
gravity thermal fuse is mounted on the heater plate in series with
the heating element circuit.
A large dropping resistor is also printed onto the heater plate which
forms part of the controllers power supply.
The element is clamped in place by a lock nut and supports the
motor at the base of the tub.
3.8.2 Heating the Water
The heater plate is positioned beneath the filter plate. A flow through water heating system is created during the
wash cycle by water flowing through the filter plate, over the surface of the element and into the wash pump.
3.8.3 Maintaining the Temperature
A printed circuit board with a temperature sensitive
thermistor is mounted on the heater plate. The sensor
parts are unservicable and if they fail a new heater plate is
required.
3.8.4 Over Heat Protection
The heater plate is only activated during a wash cycle, and is
not used in the dry cycle. The temperature is monitored by the
thermistor, and if a failure occurs with the electronic control of the
heater plate, the over heat protection is effected by the thermal
fuse on the heater plate.
The thermal fuse consists of a gravity fuse which is in series with
the heater track. In an over heat situation the thermal fuse will melt
and fall off the heater plate, disconnecting power to the element.