Baxi [E117] fault codewhat it means and how to fix it

E117 is the opposite of E118, and Baxi print it on fewer boilers. The 2012 Duo-tec 2 Combi GA user guide lists "117 — Primary System Water Pressure Too High" and marks it with the R symbol; the EcoBlue Advance Combi user guide has the same entry and adds that "Error Codes 117 and 118 can be reset by restoring the correct system pressure as described in 7.3", so there is no button to press.

The 600, 800 and Compact manuals do not print it, though Baxi's professional error-code table lists E430 as a "water pressure temporary fault" for that family, which is a different code. High pressure on a sealed system has two ordinary explanations. Either somebody filled it too far — the gauge should read 1 to 1.5 bar cold, and a system filled to 2 bar cold will be near 3 bar hot — or the expansion vessel has lost its air charge and can no longer absorb the expansion, so the pressure climbs steeply on every heat-up and the relief valve lifts at 3 bar.

A filling loop left open is the third, and it is worth checking both valves on the braided hose before assuming anything else. The relief valve is a one-way trip: once it has lifted it often does not reseat cleanly, and a boiler that shows E117 hot and E118 cold within the same week has almost always got a valve dribbling outside and a vessel that needs recharging.

1. 1

   Check both valves on the filling loop are fully closed. If one is even slightly open, close it and see whether the gauge stops climbing.

2. 2

   With the system cold, bleed a radiator until the gauge falls to between 1 and 1.5 bar. Use a radiator key and a cloth; a small amount of water will come out after the air.

   Do not bleed a hot system. The water is scalding and the reading will be wrong once it cools.
3. 3

   Run the heating and watch the gauge. On a healthy system it rises by a fraction of a bar and steadies. If it heads for 3 bar the expansion vessel needs recharging and that is an engineer job.