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Common Grant Boiler Problems & Repair Advice

Rob Wells
By: Rob Wells
Updated: 7th January 2022

Last Updated: 7th January 2022

Grant Boiler Repair Advice

Boilers are normally extremely reliable and provide our homes with heating and hot water whenever we call upon them. When things do go wrong, everyone in the house soon knows about it and to prevent your home sliding into chaos, we've put together this handy guide of repair advice.

If your home is installed with a Grant boiler, we'll be taking you through some of the most common problems you might come across and how to get the boiler going again. Should you be in any doubt at all about what's wrong with your boiler, use our free service to get quotes from reliable engineers near you.

Most common Grant boiler problems

Reset burner lock out

Safety switches will switch the burner off whenever there's a burner malfunction in your appliance. When this happens a 'lock-out reset' button will light up, pressing this will bring back normal operation. If the problem persists then an engineer will be needed to investigate.

Resetting the overheat thermostat

An overheat thermostat automatically switches off the boiler when a control malfunction causes overheating. When this happens, a red neon light will illuminate. Should you try to light your boiler but it doesn't work and the 'lock-out' reset button isn't lit, that suggests that the overheat thermostat has operated.

The boiler won't light until the thermostat is reset. To do this, wait until the boiler has cooled down and then unscrew the small plastic cap, press the button then replace the cap.

Low boiler pressure

It's a good idea to keep an eye on your boiler's pressure gauge quite often, because low boiler pressure can lead to your central heating system failing to function properly. To check the boiler pressure, simply take a look at the built-in pressure gauge, if you see anything below 1 then you may have an issue. Find out more with our guide to low boiler pressure.

Boiler leaking

Even the smallest of leaks can be a serious boiler issue. A leak could happen for one of many reasons but it tends to indicate that an internal component has broken, normally a seal or valve. This can lead to corrosion, rust or cause electrical components within the boiler to short circuit. Don't try to repair the fault yourself, instead contact an OFTEC registered engineer as soon as possible.

Hearing strange noises

If strange rumbling noises are coming from your boiler then it's likely that limescale or sludge has built-up on your boiler's heat exchanger, which is known as kettling. This build-up can restrict the flow of water within the heat exchanger causing the water to overheat, steam and boil.

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Which Grant boiler problems need an engineer?

Some common boiler issues don't even need an engineer but if in any doubt whatsoever, it's always best to contact an engineer. Use the table below to identify possible faults with your boiler.

Problem Possible cause Do you need an engineer?
No heat or hot water Broken diaphragms and airlocks, failure of motorised valves, issues with the thermostat or low water levels Yes
Leaking and dripping Most likely to be a broken internal component but it will depend where the water is leaking from Yes
Banging, whistling or gurgling noises Air in the system could be causing this, otherwise it could be that the water pressure is too low Yes
Losing pressure Could be a water leak in the system, the pressure relief valve needs replacing or due to recently bleeding radiators No, unless there’s a leak
Frozen condensate pipe This fault should be displayed on your boiler as an error code or warning notification Yes
Thermostat issues Thermostat could be turned off or not set to the correct settings (time etc.) Consider replacing
Kettling Limescale or sludge building up on the heat exchanger Yes
Radiators not getting hot Sludge or air building up in the system or an unequal distribution of heat Your radiators will need to be bled which doesn't require an engineer but if you don't feel like carrying out the task yourself
Boiler keeps switching itself off Could be low water pressure, a problem with the thermostat or a lack of water flow due to a closed valve, air or the pump not circulating the water in the system properly Yes

Grant boiler warranty

Most Grant boilers come with a 3 year warranty, but they can extend to as long as 5 to 10 years when they're installed by a G-One accredited installer. Our guide to Grant warranties will provide everything you need to know. As part of the terms of the warranty, you’ll need to arrange an annual Grant boiler service to keep it valid.

Boiler insurance and ongoing cover

If your Grant boiler warranty has come to an end, then you might want to consider boiler insurance. Any insurance that offers an annual service and safety inspections is worth thinking about. Taking out insurance can be done with your energy supplier but there's absolutely no obligation to do so.

Is it time to replace your Grant boiler

If your current Grant boiler was installed many years ago, then it might be time to consider replacing it. Replacing your boiler could lead to savings of as much as £365* a year if you live in a detached home. Take a look at the table below to see how much you could be saving depending on your current boiler rating and property.

House Type G (< 70%) F (70-74%) E (74-78%) D (78-82%)
Semi-Detached £240 £170 £150 £135
Detached £365 £255 £205 £165
Detached Bungalow £190 £135 £120 £105
Mid Terrace House £205 £145 £130 £115
Flat (Mid Floor) £95 £65 £60 £50

Figures are for England, Scotland and Wales only.

How to find the best engineer to replace a Grant boiler

The replacement of your boiler will have to be carried out by a qualified engineer, they'll either be from a national company or an independent local.

If you go with a national company, you'll be covered by big brand protection and not only have your boiler replaced but also be offered extra services like ongoing boiler cover.

Local engineers will often offer extremely competitive rates and you're likely to get a personal service throughout the installation.

When it comes to getting quotes we don't recommend going with the first one you receive, instead aim to get as many as 3. That way you know that you're getting the best deal for you.

To find trusted engineers near you, use our service to receive free quotes for a new boiler installation.

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Data Source: Energy Saving Trust, Heating Your Home: Boilers (2022)
*Based on replacing an old gas boiler with a condensing A-rated boiler with thermostatic radiator valves, programmer and room thermostat in a detached home. Figures are based on fuel prices as of November 2021.

Rob Wells

About the author

Rob Wells

Rob is another of our resident home heating experts. He manages our external partnerships, making sure you get the most up to date information.

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