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Last updated: 15th April, 2024


Boiler Won't Turn Off

Boiler Won't Turn Off

Key takeaways

  • A boiler that won't turn off requires timely intervention to maintain system efficiency.
  • Gas Safe engineers are crucial for safe and proper boiler repairs.
  • Evaluation of whether a new boiler is required should include consideration of leading brands.

When a boiler fails to turn off, it can lead to excessive energy usage and potentially harm the system. Understanding why this issue occurs and how to address it is crucial for maintaining a safe and efficient heating system.

When a boiler refuses to shut off, it can be a source of worry and inconvenience for homeowners. It is essential to understand that such an issue can arise from various faults within the heating system, ranging from thermostat malfunctions to more complex wiring problems. Addressing these issues promptly is key to ensuring energy efficiency and preventing potential damage to the boiler system.

Identifying the type of boiler you have is an initial step as different systems may present unique challenges. Seeking the expertise of Gas Safe registered engineers is advisable when faced with a boiler that won't turn off, ensuring that all repairs are carried out safely and in accordance with current regulations. For those contemplating whether a new unit is necessary, considering reputable boiler brands might lead to a long-term, cost-effective solution.

What Type of Boiler Do I Have?

Identifying the type of boiler one has is crucial for understanding how it supplies hot water and central heatingThere are three main types of boilers:

  • Combi (Combination) Boilers: These are compact units that do not require a cylinder for storing hot water. They heat water directly from the gas supply, providing hot water on demand.

  • System Boilers: They work with a cylinder to store hot water, but all major components of the heating and hot water system are built into the boiler itself, making installation easier.

  • Regular (Conventional) Boilers: These boilers necessitate both a cylinder and a water tank and are typically found in older homes. They can supply hot water to multiple taps simultaneously.

Boiler Brands such as VaillantWorcester BoschAlphaIdeal, and Viessmann offer models across these types.

When inspecting your boiler, check for:

  • The presence of a hot water cylinder (common in system and regular boilers)

  • Water tanks in the loft (a sign of regular boilers)

  • A pressure gauge, which all boilers will have to monitor boiler pressure

For Fuel: Most boilers in the UK rely on mains gas, though there are oil, LPG, or electric options, too. Reviewing one's fuel type can further clarify boiler type since, for example, electric boilers tend not to be combi boilers.

In summary, one's boiler type can be delineated by examining the boiler setup's characteristics, fuel type, and the need (or lack of) for external tanks and cylinders.

Boiler Won't Turn Off

When a boiler fails to turn off, it can lead to excessive energy usage and potentially harm the system. Understanding why this issue occurs and how to address it is crucial for maintaining a safe and efficient heating system.

Why Won't Boiler Turn Off? Possible Causes and Issues

Several issues could be at play when a boiler doesn't cease operation:

  • Thermostat Issues: If the room thermostat is set too high or has faulty wiring, it may erroneously signal the boiler to keep running.

  • Programmer Faults: A defective programmer may not correctly regulate the boiler's on and off cycles.

  • Valve Malfunctions: Specifically, motorised valves can become stuck in the open position, keeping the heating on.

  • Internal Wiring: Faulty internal wiring can prevent the boiler from receiving the correct signals.

  • Boiler Pressure Problems: High or low pressure can affect the boiler's ability to turn off properly.

  • Component Failures: Faulty thermocouples, broken sensors, or worn-out parts may contribute to the problem.

Boiler Won't Turn Off - Fixes

The following are common approaches to remedying a boiler that won't disengage:

  • Thermostat Adjustment: Lower the thermostat setting; replace batteries if necessary.

  • System Reset: Hit the reset button on the boiler to restart the system.

  • Pressure Check: Ensure the boiler pressure is at an appropriate level.

  • Valve Inspection: Check for and resolve any valve issues that may be forcing the boiler to stay on.

  • Electrical Connections: Examine the wiring for any signs of damage or loose connections.

Can I Fix a Boiler That Won't Turn Off Myself?

  • When: Some simple fixes, like adjusting the thermostat, are within the grasp of most homeowners.

  • But, complex issues involving valves, wiring, or internal components generally demand the expertise of a Gas Safe engineer. They are trained to handle common boiler problems safely and effectively.

  • Caution: DIY attempts on gas appliances can be dangerous and are not recommended.

Attempting to troubleshoot without proper knowledge or training can lead to further damage or create hazardous conditions. Regular boiler service by a qualified heating engineer can prevent many issues and ensure your boiler operates safely.

Gas Safe Engineers

When a boiler refuses to switch off, a homeowner's primary course of action should include consulting a Gas Safe registered engineer. These professionals possess the necessary qualifications to safely manage and repair gas boilers. Homeowners must understand that attempting DIY fixes on gas appliances can lead to dangerous situations, including gas leaks and carbon monoxide poisoning.

Gas Safe engineer is an individual who has passed rigorous assessments demonstrating competence in handling gas appliances. Engineers must revalidate their certification every five years to ensure their knowledge and skills remain current with technological advancements and regulatory changes. When they arrive, engineers will produce an identification card confirming their Gas Safe registration.

Selecting a heating engineer who is not registered can have serious consequences. If the engineer working on your appliance is not Gas Safe registered, their workmanship may not meet the necessary safety standards. In worst-case scenarios, this can result in legal implications and voided home insurance.

The tasks performed by Gas Safe engineers include, but are not limited to:

  • Inspecting the boiler and its associated components for signs of malfunctions or safety hazards.

  • Servicing the boiler, which should occur annually, to preemptively address potential concerns.

  • Repairing or replacing any parts that may cause the boiler to operate continuously when it should not.

Remember, it is the law in the UK that anyone working on gas appliances must be on the Gas Safe Register. A directory of Gas Safe registered engineers can be found on the official Gas Safe Register website, where one can search for qualified local engineers and verify their credentials.

Do I Need a New Boiler?

Determining whether to replace your boiler can be a significant decision. Early signs that might suggest a new boiler is necessary include persistent problems such as boiler lockouts, frequent loss of pressure, or a boiler that refuses to turn off. Issues may manifest through radiators that won't heat up or water being far too hot at the tap, implicating a malfunctioning central heating system.

An annual boiler service is fundamental to diagnose these issues. If the service reveals recurring faults, such as a defective y-plan valve or other common boiler problems, and boiler troubleshooting proves ineffective, it may be time to consider a replacement.

The age of your boiler plays a crucial role. Boilers older than 10 years tend to be less efficient and more prone to complications. If your heating system seemingly demands continuous repairs or if you experience consistent no heating or hot water situations despite regular servicing, investing in a new, more reliable boiler might be more cost-effective in the long run.

When boiler pressure issues persist, the culprit might be a faulty filling loop or deterioration within the system. If your boiler requires frequent repressurising, this is a sign that the internal components may be failing.

In summary, weighing the costs of continuous repairs against the expense of a new boiler is essential. Should your heating system exhibit significant and ongoing problems despite professional intervention, upgrading to a new boiler could enhance your home’s heating efficiency and reliability.

Best Boiler Brands

When selecting a boiler, reliability and performance are pivotal. British households frequently favour certain brands for these very reasons, often based on a history of durability and customer satisfaction reports.


Vaillant boilers are renowned for efficiency and quality. Vaillant's ecoTEC series is particularly well-regarded for its advanced technology and sustainable operation, earning the brand a strong reputation among consumers.

Worcester Bosch

Worcester Bosch remains a leading choice in the UK, lauded for their exceptional after-sale support and comprehensive warranties. As a testament to their standing, the brand consistently achieves high ratings in customer satisfaction surveys.


German-engineered Viessmann boilers offer a blend of energy efficiency and heating performance, with innovative features like the Inox-Radial Stainless Steel Heat Exchanger being instrumental in their popularity.


Ideal has made a significant mark with their Logic and Vogue series, providing a viable option for various household sizes. Their commitment to reliability and energy efficiency keeps them competitive within the boiler market.


Alpha is becoming increasingly prominent for their affordable yet dependable boilers. The E-TEC range, for instance, is designed to meet both comfort and budgetary needs, making them a solid choice for cost-effective home heating.

Boilers from manufacturers like Ariston, Baxi, and Glow-worm also find their place in many homes across the UK, while brands such as Halstead are less commonly seen but still service specific sections of the market. It's important to consider the full list of boiler brands, comparing features and support services to find the best fit for one's personal requirements.


When addressing a boiler that refuses to switch off, a methodical approach is key. Householders should initially examine the thermostat and programmer for faults by substituting batteries or resetting devices as needed. Persisting issues may hint at a deeper malfunction within the central heating system.

If DIY troubleshooting fails, it’s prudent to seek a Gas Safe engineer. Only these certified professionals can ensure the heating system adheres to safety standards. Where repairs prove uneconomical, installing a new boiler might be the most efficient resolution.

In extreme cases, continuous operation might signify an urgent defect. Immediate action—switching off the boiler and consulting an engineer—is crucial to prevent damage. Remember, regular maintenance can preempt these issues, sustaining an efficient heating system throughout the year.


At iHeat all of our subcontracted engineers are Gas Safe registered and can service your boiler swiftly and safely. Prices of an expert boiler service with iHeat start from £99.These figures might fluctuate regionally and can also depend on the specific type of boiler you own, such as a combi, gas, or oil boiler. 

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iHeat New Boiler Costs

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).

Installation Type

Price (inc VAT)

Combi to combi swap


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System to combi conversion


Get a quote

New boiler install


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Back boiler to a combi


Get a quote

System to system


Get a quote

Frequently Asked Questions

What do you do when your boiler won't turn off?

Firstly, check if the programmer or timer is set correctly and not continuously signaling for heat. Should this not be the cause, inspect the thermostat for correct operation and battery health. If these steps don't yield results, seeking professional assistance is advisable.

Why is my boiler running when the thermostat is off?

This could indicate a fault within the thermostat itself or a wiring issue. It's possible that the thermostat is not effectively communicating with the boiler, or there might be a malfunction in the boiler's electronic components that prevents it from recognizing the thermostat's off signal.

Why is my boiler continuously running?

A boiler that is constantly running may have a stuck valve, a problem with the thermostat settings, or an internal fault. Persistent running can lead to increased wear and higher energy bills, so it's important to diagnose and address this promptly.

Why is my thermostat off but the heat is still on?

In such situations, the thermostat may be faulty, the radiators might have manual radiator valves that remain open, or there could be an electrical issue causing the boiler to ignore the thermostat's signals.

Why is my thermostat not communicating with my boiler?

A lack of communication between a thermostat and a boiler can stem from a range of causes, including dead batteries in the thermostat, misconfigured settings, a distance too far from the boiler, or an electrical fault in the system.

What to do if the thermostat is not communicating?

If a thermostat fails to communicate with the boiler, it's beneficial to first reset the thermostat or replace its batteries. Should this not resolve the issue, verifying that the thermostat is within range and not obstructed by walls or large objects is a logical next step. If problems persist, an electrician or HVAC specialist may need to investigate further.

How do I know if my boiler thermostat is broken?

Signs of a broken boiler thermostat include unresponsive temperature controls, erratic heating patterns, or heating that does not align with the set temperatures. An accurate way to test is by setting the thermostat to different temperatures to see if the boiler responds accordingly.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.