PHAM NEWS | OCTOBER 2025 22 Gas & OilBoilers


Hot water delivery without a cylinder


As homes continue to evolve, so do your customers’ expectations for comfort, effi ciency and convenience – especially when it comes to hot water. Here, Graham Parkes from Navien UK explores how installers can meet rising hot water demands, and why next-generation combis may be the key.


L


ong gone are the days of waiting endlessly for the shower to heat up or scheduling baths like a military


operation. Today, the modern home is built for comfort, with families expecting instant, reliable hot water delivery that keeps pace with their varying lifestyles. With the boiler often seen as the beating heart of the home, its role is vital for ensuring hot water delivery throughout the property. Homeowners generally


expect hot water to be delivered instantly, reliably and safely, but at the same time, they tend to understand the limitations on simultaneous use and temperature. Due to the nature of combi boilers, perceptions of hot water are often shaped by a balance between convenience and these limitations. Larger homes with growing


families and high-performance appliances require a boiler that is more than ‘good enough’. In fact, homeowners are thinking about energy effi ciency, fi nding new ways they can cut energy waste and enhance their homes with smart technology.


Rising demand Now, it’s no secret that the average modern home uses more hot water than it did a generation ago. The rise of rainfall showers, large bathtubs and smart control systems has made convenience and comfort the norm. At the same time, housing density and fl oorplans are changing too. Open-plan living spaces, loft conversions and side extensions are placing higher expectations on systems once designed for simpler layouts. What’s more, customers


now expect instant hot water. The days of waiting for a cylinder to reheat, or carefully staggering usage between the kitchen and shower, are fading fast. These expectations are also converging with tighter energy effi ciency targets and a push toward lower emissions,


all of which are reshaping how hot water systems are specifi ed and installed.


Space saving Compact and eliminating the need for a cylinder, combi boilers free up valuable space in the home, allowing ample space for a storage cupboard or even a small W/C. They also reduce gas costs by removing the heat losses associated with storing hot water in a cylinder. However, in households with


Graham Parkes Commercial director at Navien UK


 Combi boilers like Navien’s NCB700 ON can match the performance of some system boilers with a separate cylinder, delivering a plentiful supply of hot water


high simultaneous demand, such as when the washing machine is running, hot water is being used in the kitchen, and someone is taking a shower – combi boilers can begin to struggle. Flow rates drop, temperatures fl uctuate, and customer satisfaction suff ers. Installers have often had to choose between oversizing a boiler (with all the ineffi ciencies that come with it) or recommending a system boiler with an unvented cylinder, which requires more space and longer installation. Fortunately, innovation in


boiler design is beginning to close that gap.


The NCB700-ON combi boiler from Navien


Going with the fl ow A new generation of combi boilers has emerged over the last few years, engineered specifi cally for high-demand homes that need excellent hot water performance without the complexity of cylinders. These advanced models integrate larger stainless steel heat exchangers, pre-heat capabilities and – in some cases – built-in thermal stores to deliver strong, stable hot water at fl ow rates previously thought impossible from a combi. A leading example of this


is Navien’s fl agship NCB700 ON, a combi boiler specialised for domestic hot water, with suffi cient output capacity to supply a large volume of hot water quickly and instantly. At the same time, it remains compact in size and is equipped with both internal and external recirculation systems. Designed to provide ample


hot water, suffi cient to run up to three showers simultaneously, the NCB700 ON matches the performance of some system boilers with a separate cylinder. It eliminates the need for additional cylinder space and avoids the energy losses associated with storing hot water, making it a more effi cient and space-saving choice. It’s an attractive option for larger homes that need more from their combi without moving to a diff erent system entirely. Alongside the fl agship


NCB700 ON, the wider NCB ON range has also been developed to provide reliable heating and hot water solutions for diff erent


household requirements. With hot water performance placed at the forefront, the range is designed around user comfort and convenience, while still delivering the effi ciency and space-saving advantages.


Meeting expectations With consumer expectations higher than ever and building standards tightening year by year, installers need to look beyond the basic combi when specifying for high-demand homes. Manufacturers are rising to the challenge. Innovations in boiler design are giving professionals the tools to meet demand without compromise. Whether it’s a growing family, upgrading a property portfolio, or a self-builder looking to minimise system complexity, it’s clear that high-performance combis are the right fi t. ◼ phamnews.co.uk/1025/39


CUT TO THE CHASE


 Traditional combi boilers struggle with high simultaneous demand


 New-generation combis use innovations like thermal stores and larger heat exchangers


 Navien’s NCB700 ON meets demand without a cylinder


Pre-heat capabilities and internal recirculation systems help stabilise hot water delivery


Eliminating hot water cylinders reduces standby heat losses


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