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Last updated: 19th February, 2024


Glow Worm Boiler Review: Ultimate₃ Combi

Glow Worm Boiler Review: Ultimate₃ Combi

Key takeaways

  • The Ultimate₃ Combi Boiler is a space-saving solution offering both heating and hot water.
  • It is recognised for its efficient performance and user-friendly control options.
  • Maintenance, servicing, and comparison with other models are critical factors in assessing its value.

Combi boilers, or combination boilers, epitomise efficiency and convenience in modern home heating. They provide both hot water and heating without the need for a separate water tank, differentiating themselves from conventional systems.

Choosing a boiler for one's home is a significant decision, entailing a balance between performance, reliability, and cost. In the expansive market of heating solutions, the Glow Worm Ultimate₃ Combi Boiler stands out as a noteworthy option. 

As a combination boiler, it offers both hot water and central heating without the need for a separate water tank, optimising space especially in smaller homes or flats.

The Ultimate₃ model boasts various control options for user convenience, fitted with an aluminium heat exchanger designed to extend its operational lifespan. Customer reviews often highlight a satisfaction with the device, citing its efficiency and recommending it to others to some degree, though it is not without its competitors. 

When evaluating the Ultimate₃, it is crucial to consider its performance metrics, maintenance requirements, and how it compares to similar models within the same category.

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Combi Boilers Explained

Combi boilers, or combination boilers, epitomise efficiency and convenience in modern home heating. They provide both hot water and heating without the need for a separate water tank, differentiating themselves from conventional systems.

Let's look at the core benefits:

  • Space-saving: With no cold-water tank or hot water cylinder, they free up valuable space.

  • Efficiency: They heat water directly from the mains, ensuring hot water on demand without wastage.

  • Cost-effective: Typically, combi boilers have fewer components, reducing installation and maintenance costs.

These benefits, however, come with considerations. Combi boilers may not suit homes with multiple bathrooms or simultaneous hot water requirements. They also rely on mains water pressure.

Installation Factors:

  • Capacity: Suitable for small to medium-sized homes.

  • Water Pressure: Requires a good mains pressure.

  • Demand: Best for homes where hot water isn't used in several locations at once.

Remember, choosing the right combi boiler depends on the household’s specific needs and professional advice should be sought to ensure the right fit.

Overview of Glow Worm Ultimate₃ Combi Boiler

The Glow Worm Ultimate₃ Combi Boiler emerges as a compelling choice for modern households, championing energy efficiency and reliable performance without compromising on build quality or value for money.

Key Features and Benefits

  • Energy Efficiency: Rated A for heating and hot water.

  • User Interface: Equipped with a bright LCD display for easy control.

  • Compatibility: Works seamlessly with the MiGo app, allowing for remote management via mobile devices.

  • Guarantee: Offers a substantial manufacturer's warranty for peace of mind.

These features aim to deliver a combination of convenience and cost savings, making the Ultimate₃ an attractive option for homeowners seeking efficiency and control in their heating systems.

Technical Specifications

  • Type: Combi boiler

  • Output: Various kW options to suit different home sizes.

  • Energy Rating: A (ERP rated)

  • Control: Compatible with MiGo app-based controls for remote operation.

Technical elements of the boiler ensure it is suitably powerful for a variety of residential needs, while also being mindful of energy consumption.

Design and Build Quality

The design of the Ultimate₃ boiler is modern and robust, offering a visually appealing aesthetic without sacrificing build quality. It is constructed with reliability in mind, ensuring longevity and enduring performance. Its compact size allows for unobtrusive installation in various home environments, reflecting Glow Worm's commitment to engineering boilers that are both functional and fit comfortably within customers' homes.

The integration of quality materials and up-to-date technology translates into a value-for-money product that does not cut corners on design or build quality.

Performance and Energy Efficiency

When evaluating the Ultimate₃ Combi Boiler by Glow-worm, it stands out for its commitment to high heating output coupled with commendable energy efficiency.

Heating Output and Efficiency

The Glow-worm Ultimate₃ is designed with a 30kW heating output capability, extending its suitability to average-sized UK domiciles, typified by 3-4 bedroom semis. In terms of energy efficiency, this combi boiler proudly bears an ErP A-rating. This achievement signifies a high level of efficiency, translating into reduced energy consumption and lower heating bills. For larger homes, there is a robust 35kW version, maintaining the same standard of efficiency.

Energy Saving Trust Endorsement

The Energy Saving Trust (EST) stands as a critical arbiter in vetting the energy efficiency of home heating systems. An endorsement from this respected body serves as a significant indicator of a boiler’s capability to conserve energy in a domestic setting. The Ultimate₃'s commendable efficiency is not only reflected in its ErP A-rating but also through its listing in the Product Characteristics Database (PCDB) with notable seasonal efficiency. This level of recognition underscores the boiler’s alignment with energy-saving measures, further cementing its status as an environmentally friendly and cost-effective heating solution.

Maintenance and Servicing

Ensuring that the Glow-worm Ultimate₃ Combi Boiler runs efficiently involves regular servicing and proactive maintenance. These processes help prevent faults and extend the lifespan of the boiler.

Regular Maintenance

Regular maintenance is essential for the optimal operation of the Ultimate₃ Combi Boiler. Service should be carried out annually by a qualified engineer to check components including condensate pipes and valves. During these checks, the engineer can also identify and rectify any emerging issues before they turn into significant problems.

  • Check the Condensate Pipe: Ensures it's not obstructed or frozen, particularly during cold weather.

  • Inspect Valves: Safety and operational valves are tested for functionality.

Manufacturers recommend these maintenance steps not just for efficiency but also for safety. An ill-maintained boiler could pose risks including carbon monoxide release.

Availability of Replacement Parts

A Glow-worm boiler's easy to service nature is enhanced by the ready availability of spare parts. The manufacturer ensures that spare parts are in stock and can be dispatched swiftly to locations around the world.

  • Original Manufacturer Quality: This guarantees compatibility and reliability.

  • Global Dispatch: Enables swift repair service no matter the location.

Proactively replacing worn parts can circumvent system failures, thus maintaining the reliability of the Ultimate₃ Combi Boiler. Having parts readily available ensures that downtime due to maintenance is minimised.

Additional Features and Innovations

The Glow Worm Ultimate₃ Combi Boiler is equipped with several notable additional features and innovations, enhancing its overall efficiency and user experience.

Advanced Control Systems

The Ultimate₃ boasts a state-of-the-art control system, which allows for precise temperature management. Its modulating Grundfos pump adjusts the flow of water based on demand, conserving energy and reducing wear on the components. Users may find comfort in the simplified interface that facilitates effortless adjustment of settings and monitoring of boiler performance.

Built-In Safety Functions

Safety is a paramount concern, and the Ultimate₃ Combi Boiler integrates numerous built-in functions. At the heart of these is the aluminium heat exchanger, known for its excellent conductivity and resistance to corrosion. This feature not only promotes longevity but also ensures consistent performance. Additionally, the boiler includes frost protection to prevent freezing during the colder months, securing the system from potential damage due to low temperatures.

Comparisons with Competing Models

In considering the Glow-Worm Ultimate₃ Combi Boiler, it's vital to assess its performance and value against its tight competition, namely the Ideal Logic and Worcester Bosch models. While comparing, it's also useful to look within the Glow-Worm range to understand how it stands within its family of boilers.

Versus Ideal Logic and Worcester Bosch

Glow-Worm Ultimate₃ 30C faces stiff competition, particularly from the Ideal Logic series and Worcester Bosch boilers. The latter is renowned for reliability and often comes with a significant warranty period—a feature that is a considerable draw for consumers. Worcester Bosch, for example, offers a range of boilers such as the Worcester Bosch 30i which, similar to the Ultimate₃ 30C, is designed for small to medium-sized homes.

When comparing the Glow-Worm Ultimate₃ 30C with Worcester Bosch models:

  • Warranty: The Ultimate₃ 30C sometimes offers extended warranties if purchased through select dealers, which can compete with the generous warranties offered by Worcester Bosch.

  • Price: Worcester Bosch models can be more expensive, thereby making Glow-Worm a potentially more budget-friendly option.

  • Installation: Both brands are typically installed by local heating engineers, with the cost being a factor to consider alongside the price of the boilers themselves.

Comparison with Other Glow Worm Models

Within the Glow-Worm range, the Ultimate₃ 30C is part of a broader portfolio that includes various combi and system boilers. It is necessary to highlight that Vaillant, another leading boiler manufacturer, is related to Glow-Worm and that since they've combined forces, the technology and quality assurance align closely.

When evaluating the Ultimate₃ 30C against other Glow-Worm models:

  • Performance: Ensure to investigate the heating output, which should align with the needs of a mid-sized home.

  • Efficiency: Look for the energy efficiency ratings as Glow-Worm offers a range of boilers with differing efficiency levels.

Boiler buyers should also note that related products within the Glow-Worm line may provide different features or benefits suitable for varied household requirements, thus impacting the direct comparison of the Ultimate₃ 30C model.

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.

Boiler costs 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


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New boiler install


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Back boiler to a combi


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System to system


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Final Thoughts and Recommendations

In evaluating the Glow Worm Ultimate₃ Combi Boiler, certain aspects stand out in terms of performance and value.

Concluding Remarks

The Ultimate₃ Combi Boiler by Glow Worm emerges as a dependable option for medium-sized homes, displaying competence with its 30.6kW hot water output and 30kW heating output. This boiler accommodates roughly three bedrooms and a couple of bathrooms without hardship. One must note that users report satisfaction with its cost-effectiveness relative to various competitors, suggesting a favourable balance between quality and affordability.

Nonetheless, potential buyers should regard after-sales support as paramount. A few recounts indicate the need for improved customer service experiences. In conclusion, the Glow Worm Ultimate₃ Combi Boiler merits consideration from cost-conscious consumers seeking effective heating solutions. Ensuring clarity on warranty and support services from the outset is advised to safeguard against any unforeseen service inconveniences.

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Frequently Asked Questions

Which is the best combi boiler on the market?

While 'best' can be subjective, consistently high-performing brands often appear in consumer surveys and industry awards. Factors such as efficiency, reliability, and after-sales support come into play.

What is the most economical combi boiler in the UK?

Economical combi boilers are those with high energy efficiency ratings, reducing gas usage and lowering bills. Several models claim top spots, but it's essential to compare their ErP labels for a true gauge of economy.

What are the disadvantages of a combi boiler?

One disadvantage is that combi boilers may struggle to meet high hot water demand simultaneously, such as running showers and taps at once in larger households. Additionally, if they break down, you lose both heating and hot water.

How much does it cost to run a combi boiler for an hour?

The cost to run a combi boiler per hour hinges on the unit's size and efficiency, current gas prices, and the specific heating settings used. For a precise figure, one must consult their unit's specifications and recent energy bills.

What is the number 1 boiler in the UK?

The title of number 1 boiler fluctuates as brands release new models and independent reviews adapt. Consumer satisfaction and reliability often place certain brands at the forefront, but this can vary year to year.

What is the best size combi boiler?

The best size for a combi boiler depends on the home's size and water demand. A smaller home with fewer bathrooms typically requires a lower kW boiler than a larger property with higher water usage.

Which boiler brand is the most reliable?

Reliability surveys and warranties can indicate which boiler brands are the most dependable. Historically, some brands repeatedly receive accolades for their longevity and fewer reported issues.

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.