Potterton [E130] fault codewhat it means and how to fix it

E130 is the flue thermostat fault, with E131 as the associated lockout on some models. A condensing appliance is supposed to send comparatively cool gas up the flue — extracting that heat into the water is precisely what makes it condensing — so a high flue temperature means heat is going somewhere it should not. On the Potterton installed base the usual reason is straightforward and depressing: these are old appliances on old systems, and the heat exchanger waterways are furred with limescale, magnetite, or both. A deposit layer only a fraction of a millimetre thick insulates the metal from the water well enough to push flue temperatures up measurably. The condition develops over years, so efficiency has usually been quietly degrading for a long time before the thermostat finally trips. It also matters for the flue: plastic flue systems are rated for the temperatures a condensing appliance normally produces, which is exactly why this trips the appliance out rather than simply logging a note.