How to reset a boiler

Modern gas and oil boilers tend to be very reliable, but occasionally they may need to be reset. For example, your boiler might shut off because of a fault that prevents it from working effectively or safely. In cases like this, it’s useful to know how to restart the appliance so that you can get your heating and hot water back.

If you haven’t reset your boiler before and you’re not sure how to do this, keep reading. In this post we set out why these appliances sometimes need to be reset and how you can do this.

Boilers are now built with a safety feature that means they shut down when they detect a fault. This is known as a boiler lockout, and it can be caused by a range of issues. For instance, your boiler may shut down if it detects that the water pressure is either too high or too low, there has been an ignition failure (for example if the fuel supply is interrupted or the burner is blocked) or if the heat exchanger is blocked.

You should be able to work out what the problem is because your boiler will display a corresponding error code. If you’re not sure what the error code refers to, you can check the manual provided by the manufacturer. 

Before resetting your boiler, you will need to address the fault that caused the lockout. If you don’t do this, you may find that you have to keep resetting the appliance - and you risk doing potentially serious damage to it.

If you think you’ve fixed the problem but your boiler still keeps shutting down, it’s likely that you have an ongoing fault. This could be something like a broken pump, a leak somewhere in the system, an electrical issue or a blocked heat exchanger. In such a situation, it is recommended that you seek advice from a Gas Safe registered engineer at the earliest opportunity.

Depending on what’s causing your boiler to shut down on a regular basis, you might find that it’s time to get a replacement. Repeatedly fixing an old, unreliable boiler can ultimately prove to be a waste of money. You may be better off investing in a new model.

Your first step should be to check your boiler to see which fault code is being displayed. Depending on the nature of the problem, you may be able to fix it yourself. For example, if the shutdown was caused because the pressure in the system was too low or high, you might be able to adjust the pressure yourself. However, it’s important not to attempt difficult or potentially dangerous repairs yourself. For anything beyond basic fixes, it’s best to get a heating engineer to take a look.

Once the problem that caused the lockout has been addressed, your boiler can be reset. Exactly how you do this will depend on the model of appliance you have. The position and appearance of reset controls varies between boilers. Sometimes they are dials and sometimes buttons. You can refer to your boiler manual if you’re not sure how to reset the appliance. Bear in mind that, depending on the particular boiler you have, you might need to press and hold the reset button for a number of seconds.

Your boiler should then fire up. Most modern appliances go through a reset sequence, which can take several minutes. If your boiler doesn’t come on again, you’ll need to call an engineer in to find out what the problem is.

Like other boilers, Viessmann appliances display a fault code when they shut down. You can consult your manual to see what the code refers to - and to take appropriate steps if required. You can also use the convenient online fault code checker to help identify the problem.

Exactly how you reset your Viessmann boiler will depend on the particular model you have. For example, you may be required to turn a dial or press a combination of buttons. If you’re unsure about this or have questions relating to any other aspect of Viessmann boiler care, don’t hesitate to contact our UK-based customer service team.

If your gas boiler suddenly stops working, it’s natural to assume that there’s a problem with the appliance itself. However, it’s important to realise that sometimes this happens because of an issue with the fuel supply. You can check if there’s a problem with your home’s gas supply by trying to turn on a gas fire or hob. If the supply has been interrupted, you should contact your gas provider or check their website for further information.

Your boiler will show a certain error code if the gas supply has been interrupted. To restart it, firstly make sure that the gas is back on and then follow the standard reset procedure. Assuming there are no other faults, your boiler should start working again as normal.

Restarting an oil boiler after running out of fuel can be a little more complicated. This is because if you tried to run the appliance without any oil, air may have been sucked into the system, meaning that the standard reset procedure isn’t enough to get your boiler working again.

If this is the case, you will need to bleed the fuel line to remove the air. The process is fairly straightforward, but if you’re not confident with this type of DIY, it’s probably best to call in a professional.

If you are doing this yourself, you should first make sure the appliance is switched off. Then you’ll need to locate the bleeder valve on the fuel pump. This valve will have a hex nut on it. Attach some rubber tubing to the valve, with the end of the rube resting in a container to catch the oil. Then loosen the nut with a wrench until it’s finger tight. At this point, you can hit the reset button on the unit controller.

Next, open the valve until oil and air start to come out. You’ll probably only need to turn the nut less than once to achieve this. Keep draining until you see a solid flow of oil and the burner is running again. You can then tighten the valve and wipe away any oil that may have spilled onto the pump or burner. Your boiler should be back to running as normal.

Knowing how to reset your boiler when it has shut down can help ensure you have access to heating and hot water when you need it. However, if you’re not sure what has caused the boiler lockout or you don’t know how to fix the problem, it’s important that you contact a heating engineer.