Potterton [E50] fault codewhat it means and how to fix it

The domestic hot water temperature sensor is what E50 reports, and it appears only on the Pottertons that make hot water themselves: the Promax Combi, Titanium Combi, Gold Combi, Promax Store and Heatmax. The Promax System and Gold System tables omit it because there is no such sensor on a system boiler.

Potterton use it as the worked example of how a two-digit code fits the two-character window — the E first, then the 50 — and the Promax user guide files it with the component faults, alongside E20, E28, E125 and E160, whose one instruction is to write the code down and call the installer or service engineer.

The fault-finding section E test is the same as for E20 — about 10 kΩ at 25 °C, falling as the sensor warms — and the Promax chart for the hot water sequence adds a practical step before condemning anything: "Clean DHW NTC sensor and DHW heat exchanger", because a sensor coated in limescale in a hard-water area reads slowly and can be marked faulty by the board. On the Assure and Promax Ultra the hot water sensor code is 321; E50 does not exist on those tables. There is no owner reset for E50 on any range.