Error code high pressure system

Anything over 2.5 bar would be considered over pressurising the boiler. Over-pressurising could be down to leaving the filling loop open too long when topping up, or it could be a sign that there’s an issue with the boiler. The ideal pressure is somewhere between 1-2 bar.

One way of getting the pressure back to a normal level if it has been over pressurised is to bleed a radiator.

You should only attempt this if you can get a pot or tub (an old butter or ice cream tub is usually good for this) under the bleed valve so you can use it to catch the water, and if the water in the system is cool. By bleeding a radiator, the pressure in the heating system and boiler will reduce and the pressure gauge will slowly start to drop. You should bleed a small amount, turn off the valve, empty the tub and check the pressure gauge.

If the pressure has dropped between 1 to 1.5 bar no further action is required. If not, the process may need to be repeated until the desired pressure is reached.

It is very important that you make sure that the valves (levers or wheels) used to fill up the system are completely closed when you've finished topping up the pressure. If both valves are left open even slightly the pressure will rise to 3 bar and the boiler will discharge water outside via a safety valve.

You should be able to hear the water flowing through the valves if they haven't been turned off correctly. If you think you have turned them off and the pressure hasn't stop rising turn them completely the other way, one at a time, as you may have got confused which way is on and off. It's clockwise for the wheel type for off and for the lever type the lever should be horizontal to the valve.

Combi boilers will automatically discharge water outside through a blow off pipe at 3 bar. This is a safety feature that protects the boiler and stops the pressure going any higher.

When the boiler is running the pressure will increase, and when it cools down the pressure reduces. Therefore, it is important to only re-pressurise the boiler when it is turned off, so a true pressure reading is shown.