Redring [Heating after switch-off]what to check

Redring put this in the Professional Service checklist, not the owner’s one, and the wording is precise: unit has been switched off using the Start/Stop button but can be heard heating the water. Their remedy is one line, replace triac PCB. Understanding why makes the severity obvious. The Selectronic controls its heating elements electronically, switching them through triacs on a power board rather than through the mechanical thermostat and pressure switch of a simple shower. A triac that has failed short stays conducting whether or not the logic board asks it to, so the element it feeds stays on.

With the shower stopped there is no flow, and an element heating standing water in a small heat exchanger is the condition every protection in the unit exists to catch: Redring’s outlet sensor should force an over-temperature shutdown, the two-stage mechanical cut-out above the heat exchanger should click the power off and, in the extreme, cut it permanently, and the pressure relief device should vent if the water flashes to steam. Those layers are why this fault usually ends in a tripped cut-out or a dripping PRD tube rather than anything worse. But they are the last line, not the plan, and an appliance relying on them every time it is switched off is not safe to keep using.

The sound is the clue: a faint hiss or a kettle-like ticking from the unit after it has stopped, sometimes with the casing warm to the touch and the display dark. This is not the cool-down. The Premier’s cool-down runs water and shows a scrolling display; the Advanced counts down from six to one; both are over inside a minute and both involve water flowing. Heating with the water stopped and the display off is the fault, and the one thing to do about it is to remove the power at the pull cord or wall isolator and leave it off until the board has been replaced.