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V. Theory of Operation
V. Theory of Operation
VA. Description of Operation/Cycle
Bosch dishwashers use separate circulation and drain pumps to reduce overall size, noise, vibration
and energy consumption. This allows the use of tall tanks, increasing overall space inside
dishwashers where full-sized plates can be placed in both upper and lower racks. Circulation pumps
are suspended by rubber straps to further reduce noise and vibration.
Bosch dishwashers use flow-through heaters instead of exposed elements used on most other
dishwashers. Water from spray arms drops to the sump and flows through the circulation pump into
the flow-through heater. Flow-through heaters prevent dishware damage from exposed elements
and allow water to be continuously filtered and heated. Bosch flow-through heaters heat water by
two degrees (ºF) per minute. All heaters are protected by a 185ºF Hi-limit (high temperature cutout)
and by a flow switch which prevents heaters from operating when no water is flowing.
Bosch dishwashers regulate water temperatures using NTC (Negative Temperature Coefficient)
sensors and electronic controls. As water temperatures increase, NTC resistances decrease.
Electronic control modules measure these resistance changes and hold wash and rinse cycles to
tight preset temperatures. Older Bosch mechanical dishwashers use thermostats to regulate water
temperatures.
Bosch dishwashers use condensation drying instead of exposed heating elements. Tanks and inner
doors are coated with bitumen (asphalt compound) which absorbs and retains heat from the heated
wash and rinse water. A condensation tube is connected to a cold zone in the tank which isn’t
covered by bitumen (on right side tank wall for UC/12 & later models and at detergent dispenser on
older UC/06 – UC/11 models). Since the cold zone doesn’t retain heat and is cooler than the areas
coated with bitumen, moisture condenses around it and exits the dishwasher through the
condensation tube. For best results, doors should remain closed until dishwashers have completely
finished drying.
