Vokèra [A04] fault codewhat it means and how to fix it

A04 is Vokèra reporting insufficient system water pressure. The appliance monitors pressure continuously and stops the burner when it drops below roughly 0.5 bar, which protects the heat exchanger from being fired without enough water passing through it. This is the most straightforward fault in the Vokèra range and the one most often resolved without an engineer. The pressure itself is the thing worth thinking about, though. A sealed heating system is closed — the water in it has nowhere to go — so a falling gauge means water has physically left the system somewhere. Once or twice a year is normal ageing. Every few weeks is a leak, and the repeated refilling that comes with it introduces fresh oxygenated water, which is what generates the black magnetite sludge that eventually costs far more than the leak would have done.

1. 1

   Read the pressure gauge with the system cold. On the Vision it is on the display; on older Vokèra appliances it is a small analogue dial low on the front of the case.

2. 2

   Locate the filling loop. Vokèra commonly fit an integral loop operated by a small lever or key underneath the appliance rather than an external braided hose, so look underneath before assuming there is not one.

3. 3

   Open it slowly and watch the gauge climb. Close it at 1.2 bar. The last part of the range fills quickly, so do not walk away.

   Do not exceed 2.5 bar cold. Overfilling makes the safety valve discharge outside, which puts you back below minimum once the system cools.
4. 4

   Close the loop completely and press reset for two to three seconds. On an integral loop, make sure the key is returned to the closed position and removed.

5. 5

   Note the date somewhere. The interval between top-ups is the single most useful piece of information if this becomes a recurring problem.