Water heating Efficiency
Water heating could have a more central role in the environmental design of homes in the future as space heating becomes less of a draw on energy due to better insulation.
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specifiers look for ways to achieve integration from the point at which the equipment leaves the factory,’ he says. ‘There will be some devil in the detail of the directive,
however, as legislating for a total system approach and actually achieving it technically are two very different things.’ Clarke says electrically-heated appliances are not
A lot of people
feel solar will answer all their problems, but the main part of the hot water system has got to be right too
– David Pepper
looked on particularly favourably under the ErP Directive, not because of the efficiency of the appliance itself, but rather the efficiency of generating electricity. He explains: ‘They are penalised because a fuel factor is applied to efficiency. Because of the relatively high carbon content of producing electricity, there is a fairly high factor applied at the moment.’ Although he says this makes electrical water heating
products less attractive, manufacturers are addressing the issue: ‘To meet the minimum requirements under the directive, water heaters will have to be better insulated, but specifically for electrical water heaters they will have to have more sophisticated control systems. The days of the on/off switching thermostat with a set point of around 60 deg C are limited because that is a pretty inefficient way to control them.’ Clarke believes that, in future, more controls will
adapt to the usage patterns of the users so that the system switches on when people want hot water rather than remaining all day at 60 deg C not being used. These ‘smart controls’ match the energy input to the water to ensure that the customer gets the temperature
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CIBSE Journal April 2010
they require at the time they require it. Controllers are also a critical component for Ian Hughes, technical director of Kingspan Hot Water Systems, and he believes it is important that the hot water system designer is aware of what he calls the ‘human- machine interface’. For Hughes, no matter how good the controller, it
is useless if the user can’t operate it easily because it simply won’t be used: ‘Designers will have to take into account the uses of the property or equipment. So, for example, it is no good expecting an elderly person with poor eyesight to try to press tiny buttons on a controller in a cupboard under the stairs.’ And, he adds, when a number of systems are trying
to work together, control systems become critical: ‘An extreme example would be an air conditioning (ac) system and a heating system that are independent of each other. The ac will be trying to cool the room as the heating system is heating it. This is a recipe for wasted energy.’ Another potential technology clash is conventional
hot water generation equipment and renewables such as heat pumps or solar systems which are increasingly being asked to work together in hot water systems as users receive financial rewards for using renewables. Indeed, Dutch believes the financial incentives being
put in place by the UK government to help stimulate the renewables market will gradually have an impact. ‘Feed-in tariffs are a welcome development, but the Government could have been a lot bolder. A 3p export
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