PHAM NEWS | APRIL 2026 26 Water Heating& Cylinders


How to avoid problems on a retrofi t project


Replacing a commercial gas water heater in an occupied building is rarely simple. Here, Gary Brushett from Adveco explains how the company has specifi cally engineered a new appliance around the realities of light commercial retrofi t projects.


isn’t just picking a high-spec unit – it’s ensuring that the unit actually fi ts the existing footprint, pipework, and fl ue route without a mid-project crisis. Choosing an appliance engineered specifi cally for these real-world constraints provides for easier retrofi t of most ageing light commercial systems without the usual headaches.


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The primary driver for modern upgrades is Part L of the Building Regulations. It mandates a minimum effi ciency of 91% for replacement commercial gas water heating. This eff ectively outlaws the like-for-like replacement of old non-condensing units.


Effi ciency upgrade Every time an aging heater reaches its end of life, it eff ectively requires replacing with new condensing technology. Modern gas water heaters don’t just meet this 91% threshold; they should comfortably exceed it, ensuring compliance isn’t a ‘near miss’ but a core performance feature. In a new build, pipes go


where the equipment tells them to. In a retrofi t, the equipment must follow the existing


Greg Brushett Sales director at Adveco


hen a water heater fails or a refurbishment kicks off , the challenge


infrastructure. Rerouting pipework in a cramped, occupied plant room is likely to be a recipe for budget creep and downtime.


To combat this, we have developed the Astute Series with a design which prioritises connection fl exibility. Series 2 models (22 to 28kW) feature four water connection points (top and side). By providing multiple entry and exit points, installers can more easily match existing supply and return runs. This isn’t just a convenience; it’s a fi nancial safeguard. Also, knowing the specifi c heights of the cold inlets and hot outlets enables contractors to assess compatibility from their desks before they even set foot on site.


Upgrading to a condensing system delivers immediate efficiency gains and ensures regulatory compliance


Old and the new Flue routing is where most retrofi t projects hit a wall. Installers should always replace the fl ue when replacing an appliance. As modern condensing units have lower exhaust temperatures, old fl ues are rarely compatible. Existing atmospheric (B11)


fl ue will not be suitable for positive pressure or condensing, as this would lead to leaking condensate and exhaust. Existing B23 fl ue is likely aluminium and aged (7+ years). Over time the aluminium will corrode in the presence of acidic condensate, so should be changed after seven years as a matter of course, meaning it should be included in the retrofi t planning.


For room sealed systems, the


fl ue is likely to be aluminium or an incompatible plastic brand. Since there will be seal tolerances it is not recommended to mix brands, so again the fl ue should be changed.


The Astute 2 Series support concentric fl ue (80/125) with vertical and horizontal kits with the latter supporting fl ue to the rear or side. It can also connect to fl ue by others with an 80mm socket. The 80/125 fl ue will support a maximum fl ue run of 20m, so it is simple to confi rm feasibility and order the correct materials upfront by checking these distances against the site survey. Retrofi tting fl ue runs is rarely a straight line though,


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Designed for easy retrofi t, Adveco’s Astute 2 Series off ers multiple connection points and various fl ueing options


and the fl ueing for the Astute 2 Series will accept up to six bends in the fl ue run. It is important to remember that when incorporating bends the maximum run must be reduced accordingly, by 1.5m per 45° bend, and by 2.5m per 90° bend. ‘Measure twice, install once’ has never been more relevant.


Room for manoeuvre In older buildings, the plant room is often tucked away in a basement or on a top fl oor. The route the original unit took in 1995 might now be blocked by a new partition wall or a smaller service lift. A successful project requires a literal walkthrough of the access route – checking door widths and lift capacities – to prevent a one-day installation from spiralling into a three-day logistics nightmare. Astute water heaters are designed to pass through a standard UK doorframe, but it is also important to remember that commercial water heaters are heavy-duty industrial components. Even a smaller Astute appliance will weigh up to 115 kilos empty and nearly 400 kilos when fi lled. So, give plenty of consideration to how the appliance is to be transported and located without causing costly damage.


Pressure points Finally, don’t overlook the basics. The Astute 2 Series off er a standard ½" BSP F gas connection and will operate with gas pressure from 17.0 to 25.0 mbar (natural gas (G20)) or 25.0 to 45.0 mbar (LPG (G31)). Remember, on installation you


need to verify the pressure under peak load, not just the static pressure.


If the supply drops below the minimum when the building starts its morning demand, you’ll face commissioning failures that are diffi cult and expensive to rectify post-install. The electrical side is simpler – a standard 230V / 50Hz / 2A single-phase supply is all that’s required, which is almost universal in UK plant rooms.


Easy upgrade


Upgrading to a condensing system delivers immediate effi ciency gains and ensures regulatory compliance. However, the diff erence between a smooth transition and a chaotic one lies in the survey. By using published data on connection points, fl ue lengths, and physical dimensions, building managers and installers can turn a complex engineering challenge into a predictable, manageable and cost-eff ective upgrade. ◼ phamnews.co.uk/426/43


CUT TO THE CHASE


 Part L of the Building Regs requires a minimum effi ciency of 91% for replacement commercial gas water heating


 Old fl ues are rarely compatible with new condensing water heaters


 The Astute 2 Series offers more installation fl exibility with multiple connection points and more fl ue options


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