The factory environment eliminates many of the unpredictable variables that plague onsite construction, such as adverse weather, inconsistent lighting, and scheduling pressure. This controlled setting allows for higher quality assurance and tighter tolerances during assembly, welding, and wiring. With access to tools and standardised procedures, technicians deliver ready-to-install systems faster, with fewer defects and higher build quality. Furthermore, the complete system can undergo Factory Acceptance Testing (FAT) before shipment. This vital step ensures that all pumps, valves, and control systems function correctly and integrate seamlessly under load, drastically reducing debugging time and risk on the final site.
Time is money, especially for commercial properties where operational downtime is costly. OSCS dramatically reduces the time spent on installation. The construction of the mechanical plant room can occur simultaneously with the construction of the building itself. Instead of weeks or months of complex pipe fitting and electrical work on site, the modular unit—which contains the complete hot water application —is delivered as a complete ‘plug-and-play’ module. It is lifted into place and requires only final connections to the building’s main services (water, power, and distribution loops). This parallel workflow can shave weeks off the construction schedule, accelerating the launch of a new build property or reopening of a renovated structure. It also allows for greater choice when locating plant functions as the structure can be located externally. This also helps to free up valuable internal space within the building.
Moving the bulk of the installation work offsite also results in a safer construction process. It significantly reduces the number of tradespeople required to work in confined, potentially hazardous, plant room spaces. Fewer personnel working at heights or handling heavy equipment in a congested area lowers the risk of accidents and improves overall site organisation. As the OSCS is delivered at the moment of requirement in the build, there are no issues with long-term on-site storage, often a source of expensive damage on busy sites which can also seriously impact project delivery timelines. This is just one of the ways offsite construction offers greater cost predictability. Labour costs are fixed in the controlled factory setting, avoiding the unpredictable escalation of site labour, which can be affected by weather delays or delivery issues. This predictable budgeting, combined with the decreased time on site, makes OSCS a compelling economic argument for high-demand, mission-critical applications like commercial water heating.
What’s In A Box?
At Adveco, by far the most popular choice of OSCS are compact plant for the delivery of basin and sink-led DHW demands. These are notably selected by restaurants, smaller schools, and general practice healthcare centres, but increasingly now also offices transforming into multi-rental or mixed-use spaces where the versatility of the approach and low-carbon system design ticks several boxes in terms of sustainability planning and, if necessary, independent system delivery on a floor-by-floor, or renter-by-renter basis.
The Adveco PPR0008 takes the award-winning FUSION hybrid water heating concept and applies it to deliver the most compact, reliable and low-carbon electric hot water OSCS. Within a 2.8×1.2×1.4 m weatherproof GRP house sits a system comprising a pair of ATSI 210-litre hot water calorifiers.
Each hot water cylinder, constructed from robust stainless steel and containing a single 1.4m2 low-level indirect heating coil is connected to an electric heat source. The two tanks are connected in series in a preheater-after heater arrangement. An ADVS-W air source heat pump (ASHP) is mounted externally to the GRP house, providing through maximised efficiency low grade renewable heat into the coil of the preheat tank. The air source heat pump provides 9.50 kW of heat input at 7°C outdoor temperatures and 6.95 kW at -7°C outdoor temperatures. The ASHP uses low-GWP refrigerant to minimise the environmental impact of the installation while extracting ambient heat from the outdoor air to preheat the incoming cold mains water in the preheat tank to approximately 50°C. With 420 litres of storage and allowing for the lower, slower reheating form the ASHP, recovery time is still just an hour, even during peak periods of demand.
An ARDENT electric boiler connects to the coil of the after heater tank to provide up to 12 kW of high-grade heat to bring the water in the hot water tank up to the desired use and storage temperature. The electric boiler uses the sealed primary loop to greatly reduce the common issues of element wear and limescale build-up in the hot water tank. The after heater tank is also additionally fitted with a reserve 6 kW direct electric immersion heater to serve as a backup heat source for system redundancy.
The completed system is supplied pre-fitted complete with all internal pipework including lagging, unvented system equipment, pumps, valves, gauges, controls, and internal mechanical and electrical connections. The system also features a wall-mounted control panel to provide power and switching to the installation, ensuring a seamless integration of all components as well as a GSM-based fault output system to alert building and maintenance services in the event of a primary appliance fault. In such an eventuality, the panel will additionally and automatically activate the backup direct electric immersion heater in the after heater tank, providing a reserve level of hot water to prevent the system from running cold. Twice per week, a timeclock connected to a destratification pump will sterilise the entire system as a method of automated legionella prevention.
On delivery, all that need be done is for the installer to connect external electrical and plumbing connections between the building and plant. For legacy public sector buildings requiring renovation and decarbonisation, OSCS provide a valuable alternative which is not tied down by the limitations of existing plant room space or location. The versatility the approach brings to any refurbishment or new build project should be given serious consideration at the earliest stages of planned development to maximise opportunities and lower overall project costs.
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