One of the biggest hospitals in the Northwest has changed its hot water feed entirely over to highly efficient continuous flow water heaters that are I2HY20 certified for 20% Hydrogen blends. The site has installed 10 Rinnai N Series 1600e units which are cascaded so that the whole system can deliver almost 10,000 litres of temperature controlled hot water on demand 24/7.


The main drivers for the decision to install Hydrogen blend ready continuous flow waters was the pressing need to lower the carbon intensity of the current storage water heaters. At the same time the hospital needed to ensure they had a reliable, robust system that would continuously deliver the vital supplies of hot water on demand. This was supported by the Rinnai N series Hydrogen Blend ready water heaters now coming with a 12-year warranty.


The Rinnai system was designed by the company’s in house Technical Services team in close cooperation with the leading building services consultancy which specified the new system. The consultancy team took full advantage of the carbon, capital expenditure and operational expenditure calculations provided by Rinnai’s specialist design team.


‘Like for Like’ is the assumed replacement when a stored water system or unit comes to be replaced. However it is important to assess the site usage and requirements during a “distress” replacement as this can be the ideal time to lower onsite carbon and increase efficiency whilst futureproofing the system for the next 10-15 years.


Says Pete Seddon for Rinnai,

“So, what can continuous flow solutions offer that can make this entire process a lot easier? Continuous flow, instant delivery of hot water delivery provides constant flows of temperature specific and controlled end-product, with units which are hydrogen blends and BioLPG ready. They are also just a one-man lift, no need for lifting gear.

‘Not only that, but if the appliance being replaced was non-condensing and the new appliance was condensing, then the flue would require changing as well as the provision to discharge condensate. Plant rooms are very rarely designed to remove equipment. This requirement to remove equipment before new is installed would have a major impact – and it takes so much time. The whole system would have to be completely shut down to allow such major works to take place and all sites, especially healthcare ones, simply cannot allow this to happen’ adds Mr Seddon.


The other benefit is the ability to cascade the Rinnai appliances so when hot water demand fluctuates the systems will regulate energy input to ensure the system is always maximising energy usage. Another benefit of cascade solution is creating built-in redundancy – this means that if one unit needs to be shut down the complete site still has ready access to hot water.

A recent CPD entitled: “Carbon and Economic Benefits of Zero Storage in Hot Water Systems,” compares the operational, economic and ecological performance of a Rinnai N series model to that of a typical storage water system.


Rinnai N series models were found to provide considerable benefits in 1st and 5th year running costs, total lifecycle costs and 1st and 5th year carbon footprints. When compared to a traditional storage water system, the Rinnai N series has been proven to deliver 20% less operational costs, 30% less fuel consumption and capital costs are reduced by 20% in the examples highlighted in the CPD.


All Rinnai continuous flow water heaters are compact and allow for significant savings in plantroom space. All percentages are evaluated at a minimum and could be higher than stated.


Rinnai’s N Series range of condensing continuous flow water heaters are officially certified for I2HY20 Hydrogen blends meaning that they are fully certified for usage with methane and Hydrogen blends making them formally ready for Hydrogen blending.



15-20 % of the running cost,

30 % of the upfront cost,

15-20 % in carbon footprint,

60 % in space,

80 % in weight.


CLICK HERE For more information on the RINNAI product range





Rinnai’s H3 range of decarbonising products include hydrogen / BioLPG ready technology, hybrid systems, and a wide range of LOW GWP heat pumps and solar thermal. Also, within Rinnai’s H3 range is Infinity hydrogen blend ready and BioLPG ready continuous flow water heaters which are stacked with a multitude of features that ensure long life, robust & durable use, customer satisfaction and product efficiency.

Rinnai’s range of decarbonising products – H1/H2/H3 – consists of heat pump, solar, hydrogen in any configuration, hybrid formats for either residential or commercial applications. Rinnai’s H3 range of products offer contractors, consultants and end users a range of efficient, robust and affordable decarbonising appliances which create practical, economic and technically feasible solutions. The range covers all forms of fuels and appliances currently available – electric, gas, hydrogen, BioLPG, rDME solar thermal, low GWP heat pumps and electric water heaters.

Rinnai H1 continuous water heaters and boilers offer practical and economic decarbonization delivered through technological innovation in hydrogen and renewable liquid gas ready technology.

Rinnai’s H1 option is centred on hydrogen, as it is anticipated that clean hydrogen fuels will become internationally energy market-relevant in the future; Rinnai water heaters are hydrogen 20% blends ready and include the world’s first 100% hydrogen-ready hot water heating technology.

Rinnai H2 – Decarbonization simplified with renewable gas-ready units, Solar Thermal and Heat Pump Hybrids. Rinnai H2 is designed to introduce a practical and low-cost option which may suit specific sites and enable multiple decarbonisation pathways with the addition of high performance.

Rinnai H3 – Low-GWP heat pump technology made easy – Rinnai heat pumps are available for domestic and commercial usage with an extensive range of 4 – 115kW appliances.

Rinnai’s H3 heat pumps utilise R32 refrigerant and have favourable COP and SCOP.

Rinnai is a world leading manufacturer of hot water heaters and produces over two million units a year, operating on each of the five continents. The brand has gained an established reputation for producing products that offer high performance, cost efficiency and extended working lives.

Rinnai’s commercial and domestic continuous flow water heaters offer a limitless supply of instantaneous temperature controlled hot water and all units are designed to align with present and future energy sources. Rinnai condensing water heaters accept either existing fuel or hydrogen gas blends. Rinnai units are also suited for off-grid customers who require LPG and BioLPG or rDME.

Rinnai products are i2HY20 certified, A-rated water efficiency, accessed through multiple fuel options and are available for purchase 24/7, 365 days a year. Any unit can be delivered to any UK site within 24 hours. Rinnai offer carbon and cost comparison services that will calculate financial and carbon savings made when investing in a Rinnai system. Rinnai also provide a system design service that will suggest an appropriate system for the property in question. Rinnai offer comprehensive training courses and technical support in all aspects of the water heating industry including detailed CPD’s. More information can be found on Rinnai’s website and its . . . . 

 . . . . “Help Me Choose” webpage.


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