Boiler Fault Finder

Domestic Hot Water Flow Switches

Domestic hot water flow switches Reasons a domestic hot water flow switch will fail to operate: Switch contact faulty Internal paddle / turbine / wheel not free moving (stiff/seized/reversed water flow) Punctured / perished rubber diaphragm Blocked pressure differential sensing pipes (scale deposits) Damaged / loose wiring harness Seized bearing plate spindle / out of alignment A demand for domestic hot water will either activate a turbine arrangement, a paddle / wheel arrangement or a rubber diaphragm arrangement, all of which communicating to a micro switch assembly, transmitting a signal to the printed circuit board for correct operation. To test a domestic hot water flow switch (on a demand): Pressure differential type: Visually assess whether bearing plate spindle is rising through gland nut, activating the micro switch assembly above. (No spindle movement may be due to a perished rubber diaphragm and/or seized bearing plate spindle and/or blocked pressure differential sensing pipes. Where pressure differential sensing pipes exist, it may save time to check for any scale deposits present, prior to stripping down the flow switch assembly to assess the spindle and/or diaphragm). Inline paddle/turbine/wheel type: A continuity check of the wiring harness at the printed circuit board end will ascertain correct operation of integral switch and the integrity of wires also….

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