Vokera Boiler Pressure: Topping Up Vision, Evolve and Compact

What pressure should a Vokera boiler be?

A Vokera boiler should be at 1 to 1.5 bar with the boiler off and the system cooled to room temperature. That is the figure in the user instructions for both the Vision combi and the Compact A, and the Evolve instructions say the pressure should be about 1 bar at room temperature. The same manuals give 0.5 bar as the minimum: below that, the boiler may lock out.

The reading rises when the heating runs, because hot water expands. That is normal as long as it stays well below 3 bar, the point at which Vokera's safety valve opens. For what a normal rise looks like and how Vokera compares with other brands, see our guide to normal boiler pressure.

Where is the pressure gauge on a Vokera boiler?

On the Vision and Compact the pressure gauge is a dial on the lower front of the boiler, part of the control panel. On the Evolve there is a dial gauge on the underside of the boiler, and the pressure also shows in bar on the digital display of the REC10 control panel. If you cannot see a gauge on the front, crouch down and look underneath.

Vokera pressure by model

These figures come from the Vokera user, installation and servicing manuals for each model, which Vokera publishes on its website. Vokera has made several versions of each range over the years, so if your boiler has a different name on the front, such as Vision Plus or Compact HE, use the manual for that model.

Vokera low pressure codes: A04 and E041

On the Vision and Compact, low pressure shows as A04, which the manuals describe as insufficient system water pressure. The action Vokera gives is to check and refill the system pressure, reset the boiler and check it works. Our A04 page explains the code and what to check if it will not clear.

The Evolve works differently. Its installation and servicing instructions describe a water pressure transducer that reads the pressure electronically. When the pressure falls below 0.3 bar, the display shows E041 with the message WATER TRANSDUCER LOAD THE SYSTEM, and the manual gives you a 10 minute window to open the filling tap and bring the pressure back to 1 to 1.5 bar. The same manual lists a separate transducer fault, E042, for when the sensor itself has failed.

Not every Vokera code starting with A is about pressure. Vokera A03, for example, is a fan fault, so check the code against the right page before you start topping up.

Where is the filling loop on a Vokera?

On Vokera combi boilers the filling loop connects to two valves underneath the boiler. The Vision, Compact and Evolve manuals all say to locate the filling valve connections, usually beneath the boiler, and attach the filling loop to both. The loop is a temporary connection: it is attached for filling and removed afterwards, as UK water regulations require for a loop that links the drinking water supply to the heating.

If the loop is not attached, it is usually stored with the boiler paperwork or in the cupboard under the boiler. The Evolve manual says a temporary filling loop is supplied with the boiler. Our filling loop guide shows the common types and what to buy if yours has gone missing.

How do I repressurise a Vokera boiler?

To repressurise a Vokera boiler, attach the filling loop, open the filling valve slowly until the gauge reads 1 to 1.5 bar, then close the valve and remove the loop. The steps below follow the Vokera user instructions.

1. Switch the boiler off and let it cool. Vokera's target is based on the pressure with the boiler off and at room temperature, so wait until the radiators are cool.
2. Find the filling valve connections underneath the boiler.
3. Attach the filling loop to both connections, hand tight.
4. Open the filling valve slowly until you hear water entering the system.
5. Watch the gauge. On the Evolve, you can watch the dial underneath or the digital display.
6. Close the filling valve when the gauge reads between 1 and 1.5 bar.
7. Remove the filling loop from the connections, catching the small amount of water that comes out.
8. Reset the boiler if it is showing A04 or another lockout, then switch it back on.

If you have an Evolve showing E041, you can do this with the boiler on, because the display tells you when the pressure is back. Keep an eye on the 10 minute window described in the manual. If the boiler locks out before you finish, complete the top-up and then reset it. Our general guide to resetting a boiler explains when a reset is safe.

Vokera boiler pressure too high

If the cold reading is above 1.5 bar after topping up, let some water out by bleeding a radiator until the gauge is back in range, and check that the filling valve is fully closed. A valve that lets water through when closed will push the pressure up again.

The Vokera manuals say the safety valve lifts at 3 bar and discharges through a pipe that runs outside with a continuous fall. If the pressure climbs close to 3 bar each time the heating runs, or that pipe is dripping, the cause is more likely the expansion vessel than the filling loop. Our guide to boiler pressure that is too high explains the next steps.

The Vokera expansion vessel and system size

The expansion vessel inside the Vision and Compact holds 8 litres and is pre-charged to 1 bar, and the manuals say it can cope with a heating system of up to 74 litres. The Evolve uses 8 or 9 litre vessels, also at 1 bar. In a larger house with many radiators, an installer should have added extra expansion capacity. If the pressure swings widely between hot and cold, that is one of the things an engineer will check. Our guide to the expansion vessel explains how it is tested and recharged.

When to call a Gas Safe registered engineer

Book a Gas Safe registered engineer if:

• The pressure drops below 1 bar again within days or weeks.
• A04 or E041 returns even though the gauge showed 1 to 1.5 bar after filling.
• The display shows a transducer fault such as E042.
• The pressure goes above 2.5 bar with the heating on, or water drips from the pipe outside.

Tell the engineer your model, the cold and hot pressure readings and how often you have topped up. If the pressure keeps falling, our guide to a boiler losing pressure lists the checks you can make first.