Vokera Boiler Problems and What to Do About Them

Updated July 2026 · Emergency Plumber Chelsea

Vokera boilers are common in London flats and conversions. Ranges such as the Unica, Vision, Evolve, Compact and Easi-Heat Plus are compact wall-hung combis that fit into kitchen cupboards, which is why you find so many of them in Chelsea's mansion blocks and converted townhouses. Before you do anything, note the model name from the front panel, the reading on the pressure gauge, and any code or flashing light on the display. Codes differ between Vokera ranges and generations, so the manual for your exact model, usually printed on a label inside the flap or available from Vokera's website, is the final word on what a code means.

Low pressure is the most common Vokera problem. A sealed heating system needs water pressure for the pump and heat exchanger to work, and when the gauge falls below about 1 bar with the heating cold, the boiler will first struggle and then stop, showing a low pressure warning. Many Vokera combis have a filling tap or lever on the underside of the boiler; others use a braided silver hose between two valves on the pipes below. With the heating off and cool, open the filling valve slowly, watch the gauge rise to around 1 to 1.5 bar, then close it fully. Our guide to what pressure a boiler should be explains the reading.

Pressure that keeps dropping is a separate fault. Topping up once after bleeding radiators is normal. Topping up every week means water is escaping. Look for drips under radiators and valves, damp patches on ceilings below, and the small copper pipe that comes out through the wall near the boiler. If that pipe is dripping, the pressure relief valve is letting water out, often because a flat expansion vessel is making the pressure spike when the heating warms up. Our guide to a boiler that keeps losing pressure covers the usual culprits, including leaks hidden under floors.

A lockout means the boiler tried to light, did not detect a flame and shut itself off for safety. On many current Vokera models this shows as A01, and on older ones as a flashing light with a reset symbol. Check the hob lights, because if it does not, the problem is the gas supply, and on a prepayment meter it may simply be credit. In cold weather, check the plastic condensate pipe outside. If it freezes, water backs up inside the boiler and it will lock out every time. Our frozen condensate pipe guide explains how to thaw it with warm, not boiling, water. Then press reset once. Our guide to boiler ignition lockout explains what an engineer checks if the lockout returns.

Heating working but no hot water is the next most common Vokera complaint. On a combi, the diverter valve switches the boiler's heat between the radiators and the taps, and a flow sensor tells the boiler that a hot tap has been opened. If the diverter valve sticks, you get hot radiators and cold taps. If the flow sensor fails, the burner never fires for hot water at all. Check the hot water temperature setting and open the tap fully before assuming a fault, because a combi needs a minimum flow rate to start. Lukewarm water that has slowly got worse is more likely to be limescale in the plate heat exchanger, which is common with hard London water. Our guide on a boiler not heating water goes through each of these.

Water leaking from a Vokera boiler should always be taken seriously. A drip from underneath can be a weeping pipe joint, a pressure relief valve, a pump seal or a heat exchanger that has started to corrode. Switch the boiler off, isolate its electrical supply if you can do so safely, put a container under the drip and keep people away from the wet floor. Do not take the casing off. If water is getting near electrics, or the ceiling below is wet, treat it as urgent. Our guide on what to do if your boiler leaks sets out the steps in order.

Noises have a handful of causes. A gurgle when the heating starts usually means air, and bleeding the radiators followed by a pressure check often cures it. A rumble or kettle-like boiling sound, called kettling, usually means limescale or sludge restricting flow through the heat exchanger, so the water overheats in spots. A loud whine or grinding can be a pump on its way out. A boiler that fires, runs briefly and shuts down again over and over is short cycling, which points to a flow, thermostat or sizing issue. Our guides to a boiler making banging noises and a boiler that keeps turning on and off explain what each means.

Know when to stop. Reset once or twice at most. If the same fault returns straight away, if you need to top up the pressure more than about once a month, if water is visible inside the casing, or if the boiler is making a new and loud noise, stop using it and book an engineer. If you smell gas, leave the property, do not use switches and call the National Gas Emergency Service on 0800 111 999 from outside. Signs such as a yellow or floppy flame, sooty marks around the casing or unexplained headaches in the household can point to carbon monoxide, and our guide to the signs of carbon monoxide from a boiler covers what to do.

Many Vokera faults can be spotted early. An annual service checks the condensate trap, the burner and ignition electrode, the flue, the expansion vessel charge and the pressure relief valve, which are the parts behind most of the problems above. Our boiler service covers Vokera boilers across SW3 and SW10. If yours is older and the faults are becoming regular, our guide on how long boilers last helps you decide whether repair still makes sense.

Emergency Plumber Chelsea sends Gas Safe registered engineers to Vokera boilers in Chelsea, Knightsbridge, Sloane Square, South Kensington and Fulham. Tell us the model, the code on the display and what the pressure gauge reads, and we can often narrow the fault down before we arrive. Our boiler repair service agrees the work before it starts, and there is no call-out fee on jobs over 3 hours. Call 020 3002 6667.

Quick tips

• Note the model, the gauge reading and any code before you press reset.
• Low pressure: top up to about 1 to 1.5 bar with the heating cold, then close the filling valve fully.
• A lockout in cold weather often means a frozen condensate pipe outside.
• Hot radiators but cold taps on a combi usually means the diverter valve or flow sensor.
• Any leak from the boiler: switch it off, catch the drip and call an engineer.

FAQs