Keston Boiler in a Grade II Listed Liverpool Home
- 2 days ago
- 12 min read
This is Part Two of the Halewood Road Project. Part One covered the brief, the plant room build, the 45kW commercial heat-only boiler, the dual Y-Plan zoning, and the removal of the old vented tanks. This post focuses on the technical detail: why we chose a Keston boiler, how a plate heat exchanger solved the problem of an old steel system, the six-month wait for listed building consent on the flue, and what it took to route that flue through a Grade II listed property in Gateacre without making a mark on the building. If you have a large, older, or listed property and you are trying to work out how to upgrade the heating without ripping the whole house apart, this is worth reading.
Why We Specified a Keston Boiler in a Grade II Listed Liverpool Home
The Keston range is not the first name that comes up when most homeowners are searching for a new boiler, and that is precisely why it is the right choice in certain situations. So why Keston Boiler in a Grade II Listed Liverpool Home Keston boilers are built around difficult installations. The engineering brief for this range has always centred on flexibility: flexible flue options, suitability for challenging locations, and reliable performance in environments where the standard choices simply do not fit.
In this property, the boiler was going into the basement. The flue needed to exit the building discreetly, run along the exterior, and terminate at the back of the building, all without visually altering a Grade II listed facade. That rules out most standard domestic boilers immediately. Keston's concentric flue system, which combines the exhaust outlet and air intake in a single pipe configuration, is designed with exactly this kind of routing in mind. The flue can be extended, turned, and terminated at high level without the performance penalties you would see on a domestic boiler pushed beyond its design limits.
Keston boilers are also heat-only (sometimes called regular or conventional boilers), meaning they work with a separate hot water cylinder rather than producing hot water on demand. For a property with high hot water demand across multiple bathrooms, this is the correct approach. The stored supply means you are not waiting for the boiler to respond every time someone turns a tap on. Our boiler installations page covers how heat-only and combi configurations compare, but for a property this size, the choice is straightforward.
The boiler operates on the pressurised side of the system. This distinction matters, and it brings us to the most technically interesting part of this installation.
The Plate Heat Exchanger - Protecting a New Boiler From an Old Steel System
Watch Ste Walk Through the Installation
Our engineer Ste explains the plate heat exchanger setup and the listed building flue route on camera, filmed on site at the Gateacre property.
This property has a lot of old steel pipework. Old houses commonly do. The steel pipework and steel radiators in an open-vented system corrode slowly over time, releasing iron oxide particles, commonly called sludge, into the water. When you introduce a new, high-efficiency condensing boiler into an old open-vented system, that sludge and oxygen content will attack the boiler's heat exchanger. The boiler will fail prematurely, and any warranty is likely to be voided.
The conventional solution is to replace all the steel pipework and radiators with modern copper and aluminium equivalents. On a property like this, with steel running through multiple floors and throughout the structure of the building, that means significant disruption: lifting floors, opening walls, replastering. In a listed building, that level of work has planning implications of its own. It is expensive, disruptive, and in this case entirely unnecessary.
Instead, we installed a plate-to-plate heat exchanger between the new pressurised circuit and the existing open-vented circuit.
A plate heat exchanger is a compact unit made up of corrugated metal plates stacked together. Two separate fluid circuits flow through alternate channels between the plates. Heat transfers from the hot fluid to the cooler one through the plate surfaces, but the two fluids never mix. In this installation:
The pressurised side carries clean water flowing through the Keston boiler, the unvented cylinder, and clean copper pipework.
The open-vented side remains as it is, with the loft tank intact, at low pressure, carrying the existing steel pipework and steel radiators.
The Keston boiler heats the water on the pressurised side. That heat transfers across the plate exchanger to the open-vented side. The pump on the open-vented circuit, responding to the room thermostat, then distributes that heat through the radiators. The boiler never sees the old water. The steel system continues to function without modification. The homeowner gets the efficiency and reliability of a new pressurised system without the cost and disruption of a full strip-out.
This kind of approach is not unusual in commercial heating, where mixed systems and complex existing infrastructure are the norm. Applying that thinking to a large domestic property with old steel is exactly what our commercial gas engineers are qualified to do. The solution is more robust and far less expensive than the alternative.
If you have an older property with steel pipework and you are thinking about a new boiler, do not assume you have to replace everything. Get a proper assessment first. Request a quick quote and we can look at what the system actually needs.
The Listed Building Challenge - Six Months Without Heating
This property is Grade II listed. In England, that means it is recognised as a nationally important building of special interest, and any works that affect its character must be approved by the local planning authority before they begin. Under the Planning (Listed Buildings and Conservation Areas) Act 1990, carrying out unauthorised works to a listed building is a criminal offence. There is no retrospective approval process: if you do the work without consent, you may be required to undo it at your own cost. Grade II is the most common listing, covering around 91.7% of all listed buildings in England according to Historic England, but common does not mean straightforward. The constraints are real, and the process takes time.
The challenge on this job was the flue. Running a flue pipe through or along the exterior of a listed building is an alteration to the fabric of the building and requires listed building consent from the local authority. The customer had been without a functioning heating system for six months while that consent was being obtained. That is not unusual on listed buildings. The process is thorough because it needs to be, and trying to rush it or go around it creates far bigger problems later.
Our relationship with this customer goes back years. Darren Wilson first met them when they were students. He has installed heating in every house they have lived in since, watching each move take them to a bigger, more complex property. By the time they reached this one, a large Grade II listed house in Gateacre, the trust between customer and engineer was well established. That matters on a job where the customer needs to be confident in the advice they are getting, particularly when that advice involves telling them to wait six months for a planning decision rather than finding a shortcut.
We were involved in advising on the flue route early in the process, so that when consent was granted, the installation could proceed efficiently. Understanding what the planning authority will and will not accept, and presenting a flue route that is both compliant and aesthetically sympathetic, is part of the value a specialist engineer brings to a job like this. Our commercial gas safety work frequently involves navigating regulatory and building control requirements, and this listed building consent process followed the same principle: get the paperwork right before the pipe goes in.
Routing the Flue: From Basement to Building Exterior
Once consent was granted, the flue installation itself was a considered piece of work. The Keston boiler sits in the basement. The flue needed to exit the building, travel along the exterior, and terminate at the back of the property at a point that met Building Regulations requirements for clearance from windows, doors, and boundaries.
Stephen Boardman, our commercial engineer on this project, planned the route carefully. The flue exits the basement, runs close to the ground along the side of the building, then rises to mid-height at the rear before terminating with the combined exhaust and air intake. Keeping the flue low to the ground for as long as possible minimised its visual impact on the building's main elevations. The termination point at the back of the property is functional without being prominent.
The local planning authority had approved the route on one condition: the flue needed to match the existing building. The property has black cast-iron-effect downpipes and guttering. We specified the flue in matching black. The council were satisfied, the consent was confirmed, and the installation proceeded.
It is a small detail, but it is the kind of detail that determines whether a listed building application succeeds or fails. Presenting a proposal that respects the building's existing palette rather than asking the authority to accept something out of character is practical advice that saves time and application cycles. This is experience that comes from working on older and listed stock across Liverpool and the wider North West. Our commercial boiler service team has completed work in everything from Victorian terraces to 1930s institutional buildings, and the approach to flue routing and building consent follows similar principles each time.
Hive Smart Controls: Running a Complex System Simply
A system this involved, two Y-Plan zones, an unvented cylinder, a heat-only boiler, and a plate heat exchanger, needs straightforward controls. The more complex the engineering, the more important it is that the homeowner can manage the system without thinking about the plumbing behind it.
We integrated the system with Hive smart controls. Hive is a well-established platform in UK domestic heating, and it works well for zoned systems because you can set individual schedules and temperatures for different parts of the building from a single app. The main house and any secondary zones can be managed independently, remotely if needed, without the homeowner having to understand the mechanics of the Y-Plan valve configuration underneath.
Smart controls on a system this size deliver genuine running cost benefits. A large property with an older, single-zone approach tends to heat rooms and spaces that are not being used. Intelligent scheduling, combined with the dual-zone configuration installed here, means the system fires only when and where it is needed. The Keston boiler's efficiency rating provides the baseline, and the Hive controls deliver it correctly in practice.
For anyone interested in upgrading the controls on an existing system, our page on central heating upgrades covers the options. A control upgrade is one of the most cost-effective improvements you can make to an older system without replacing the boiler itself.
The Unvented Cylinder: High-Pressure Hot Water Throughout
We covered the unvented cylinder in Part One of this series, but it is worth returning to it here in the context of the plate heat exchanger. The unvented cylinder sits on the pressurised side of the system, receiving clean, mains-pressure water. It is completely isolated from the old open-vented circuit by the plate heat exchanger. This means the cylinder is always fed with clean water, at consistent mains pressure, without any risk of contamination from the old steel side of the system.
The result is strong, consistent hot water pressure at every tap and shower in the building. In a house this size, with multiple bathrooms and potentially several people using hot water simultaneously, a well-specified unvented system is the right choice. Vented systems simply cannot deliver the same pressure at upper-floor outlets without a booster pump, which adds complexity and noise.
Our engineers are G3 qualified, which is the legal requirement for installing and commissioning unvented hot water systems. If you are considering an unvented hot water cylinder for your property, the qualification and experience of the installer matters. The system includes several safety devices that must be set up correctly at commissioning, and the annual servicing requirement is mandatory under most manufacturers' warranties. We offer unvented cylinder servicing across Liverpool and the wider North West.
What This Project Means for Larger and Listed Properties
The Halewood Road project is a useful illustration of what is possible when a heating upgrade is approached with the right expertise rather than the standard template. The property had every complicating factor: old steel infrastructure, a listed building constraint on the flue route, high hot water demand, multi-zone requirements, and a basement location for the plant room.
None of those factors required the house to be torn apart. The plate heat exchanger preserved the existing radiator circuit. The Keston boiler provided the flue flexibility the listed building required. The planning process, though slow, produced a consent that protects both the building and the installation against future challenge. The smart controls give the homeowner an accessible interface for a technically complex system.
This is not the kind of job that a standard domestic installation company takes on. It requires commercial-grade knowledge applied to a residential setting, regulatory understanding, and experience with non-standard equipment. Our commercial gas engineers hold the qualifications and have the project experience to handle it correctly.
If you own a large property, an older property with mixed pipework, or a listed building that needs a heating upgrade, we are worth speaking to before you assume the job is too complicated or too expensive. Often the engineering solution that looks complex from the outside is more straightforward in practice, once you know what you are working with.
See more case studies and commercial projects on our commercial heating in Liverpool blog post, or read our earlier case study from Tree Tops Nursery.
Frequently Asked Questions
What is a plate heat exchanger and why is it used in older properties?
A plate heat exchanger transfers heat between two separate water circuits without the water mixing. In older properties with steel pipework, it allows a new, high-efficiency boiler to operate on a clean pressurised circuit while the existing open-vented steel circuit continues to function as normal. This avoids the cost and disruption of replacing all the old pipework and radiators. It is a common approach in commercial heating and increasingly used in large residential installations with legacy steel infrastructure.
Can I install a new boiler in a Grade II listed building?
Yes, but any works that affect the exterior of a listed building require listed building consent from the local planning authority before work begins. This includes running a flue through or along an external wall. The process takes time, and timescales vary by authority, but it is manageable with the right preparation. Choosing a boiler with flexible flue options, such as a Keston, and presenting a sympathetic flue route to the planning authority significantly improves the chances of a straightforward consent. Do not attempt to install a flue on a listed building without obtaining consent first.
How long does listed building consent take for a heating installation?
Listed building consent applications are typically decided within eight weeks, though complex cases or those requiring additional information can take longer. In practice, the total time from application to decision, including preparation and any back-and-forth with the authority, is commonly three to six months. Planning this stage into the project programme from the outset avoids leaving a property without heating while waiting for approval.
Is a Keston boiler right for my property?
Keston boilers are particularly well suited to properties where the flue route is difficult: long runs, unusual angles, or constraints imposed by listed building status or tight urban sites. They are heat-only boilers, so they require a separate hot water cylinder, which makes them most appropriate for properties with high hot water demand. If your property has a challenging flue requirement or you are replacing heating in an older building, Keston is worth discussing with a qualified engineer. Contact us to discuss your specific situation.
Do I need to replace steel radiators when fitting a new boiler?
Not always. If the steel radiators are in reasonable condition and the system is open-vented, a plate heat exchanger can isolate your new boiler on a clean pressurised circuit while the existing steel circuit continues to supply the radiators. This approach preserves the existing infrastructure and reduces installation cost significantly. A power flush of the steel circuit is advisable before installation to remove accumulated sludge. Our power flushing service is available across Liverpool and the North West.
What areas do DD Wilson cover for commercial and complex residential heating projects?
We cover Liverpool, Wirral, Merseyside, Cheshire, South Lancashire, and the wider North West. For commercial and complex residential projects, we work across the region. See our areas we cover page for full details, or call us on 0151 739 8945 to discuss your project directly.
Can my heating system be upgraded without disrupting the whole house?
In most cases, yes. As the Halewood Road project shows, careful specification means you can introduce modern, efficient equipment into an older property without dismantling the existing infrastructure. The right approach depends on what you have got and what you want to achieve. A thorough site assessment before quoting means we can give you an accurate picture of your options. Central heating maintenance and system assessment are part of what we offer before any upgrade work begins.
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DD Wilson Gas And Heating Engineers Ltd has been installing, upgrading, and maintaining heating systems across Liverpool and the North West for over 27 years. Family-run, Gas Safe registered (583586), and experienced in commercial-grade residential installations.
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