Fit for purpose

Andrews Water Heaters, DHW, domestic hot water, Energy efficiency
In pursuit of efficient water heating — Chris Meir.

City commuters are increasingly cycling to work to keep fit, beat traffic jams and reduce their travel costs. This has directly resulted in an increase in demand for changing facilities in the workplace, including showers. Chris Meir of Andrews Water Heaters, explains how businesses can cater for cyclists whilst remaining energy efficient.

According to the last Census, many workers are swapping four wheels for two to travel to work. Between 2001 and 2011, the number of people living in London who cycled to work more than doubled. There were also substantial increases in other cities including Brighton (increasing by 109% between 2001 and 2011), Bristol (94%), Manchester (83%), Newcastle (81%) and Sheffield (80%) (1).

During those years, rising travel costs, tax exemptions such as the Government’s Cycle to Work Scheme, traffic congestion as well as improved awareness of environmental issues have all incentivised commuters to get on their bikes. A British Council for Offices survey identified this as the main reason why 92.6% of respondents said that showers are now the most desirable workplace facility (2). What’s more, over half of the respondents in the survey said that the quality and availability of workplace cycle facilities influences their career decisions.

Forward-thinking companies are already recognising the benefits of looking after the wellbeing of their staff by making such provisions. Others may follow suit to attract the most talented workforce.

This presents significant opportunities for specifiers who can marry the demand for shower facilities with the drive towards energy-efficient buildings. By choosing the correct setup, specifiers can offer business owners the winning combination of reduced energy bills and a more attractive workplace to potential employees.

Traditional commercial systems employ a boiler, which generates space heating and heats a calorifier to produce hot water. Installing a higher-output boiler would naturally accommodate a higher demand for hot water, as well as heating. However, while demand grows for hot water, the need for space heating is declining somewhat. The level of insulation in modern buildings means less heat is lost, so central heating can run at lower temperatures for a shorter time. This, coupled with the popularisation of underfloor heating systems, which work at lower temperatures than radiators, high-output boilers are not always the most suitable choice.

So, in the absence of additional heating requirements, this approach creates unnecessary waste as the boiler will be oversized for the overall system. It is also likely to contribute to increased energy expenditure.

Generating demand for showers, cyclists using a cycle superhighway in south London. (

One solution is to install a separate, dedicated water heater to cater for the hot-water demand without wasting energy on heating. Separate space-heating and hot-water systems generally provide lower running costs, energy consumption and carbon emissions because the hot water energy load can be more suitably matched to the water heater output. In addition, since water is heated from a low mains temperature (at a supply temperature of around 10 to 60°C), high levels of condensing operation can be achieved, contributing to further savings. Finally, heating-system boilers can be switched off in the warm summer months, and the electrical consumption of boilers, primary pumps and secondary pumps can be reduced.

The Carbon Trust has recognised this fact in its publication ‘Hot water boiler equipment: A guide to equipment eligible for Enhanced Capital Allowances’, which explains: ‘Dedicated water heaters enable the separate provision of hot water and space heating. This avoids the energy wastage that arises from the cycling of boilers to maintain the temperature of water heating circuits and tanks when space heating is not required.’ (3)

So, which is the best type of water heater to optimise the system?

A direct gas-fired storage water heater is perfect for commercial applications such as office buildings. Typically, the heat exchanger is located within the storage cylinder so heat is transferred directly into the stored water. To further improve efficiency, this sort of water heater is designed to heat water via energy from the combustion process and to collect latent heat from the condensing of the flue gases from within the heat exchanger.

It is critically important to size a direct gas-fired water heater correctly. Too big will waste energy, and too small will not produce enough hot water. Thankfully, help is available for this. The CIBSE ‘Public health and plumbing engineering’ guide part G1 provides assistance, and progressive manufacturers offer helpful sizing calculation tools.

For example, the new and improved Size-it tool from Andrews Water Heaters allows users to manage a portfolio of projects and tailor the sizing to their exact property type and hot water requirements. The online tool is accessible from any device and provides up-to-date legislative guidance which can be downloaded as a summary or detailed report.

Some health fads come and go, but as our cities face increasing pressures on their transport infrastructure, the popularity of cycling to work looks set to stay. Specifiers can in turn seize on the business opportunities offered by this trend, whilst helping their customers attract and retain valued employees.

Chris Meir is sales director at Andrews Water Heaters.

1. bbrf.pdf


3. data/file/376177/ECA758_Hot_water_ boiler_equipment.pdf

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