The future for gas boilers efficiency

How are manufacturers achieving such high levels of efficiency and will it ever be possible to create a gas boiler that's 100% efficient?.

All new and replacement gas-boiler installations (with limited exceptions) must now run at over 86% efficiency.

Some boiler manufacturers are now only building SEDBUK A-rated models, which are over 90%.

With ongoing dedication to improving the efficiency of new boilers, how are manufacturers achieving such high levels of efficiency and will it ever be possible to create a gas boiler that's 100% efficient?.

Martyn Bridges, Worcester's director of marketing and technical support, sheds some light: "Gas domestic heating became popular here in the seventies when North Sea gas became a viable option for the UK to pump.

Until relatively recently, gas boilers were built in cast iron with a simple ignition system, which was often open flue.

In many instances boilers sat in a fire behind a back boiler.

"Many of these back boilers (regular units) had a permanent pilot light, which means that efficiency was compromised quite significantly.

In fact with a permanent pilot light it isn't possible to reach a SEDBUK band D rating (78 -- 82% efficiency).

In the late nineties these permanent pilot lights were eliminated.

"Energy efficiency has been an increasingly important factor in Government environmental policy for a good number of years.

In 1984, the first energy-efficiency rules were introduced within the Building Regulations.

They were extensively tightened in 2002 with the introduction of the SEDBUK (seasonal efficiency of domestic boilers in the UK) rating system within Part L1.

"Further strengthening then occurred in the 2004 updated regulations and precipitated the market's rapid transference to condensing boilers.

In the spring of 2005, all new and replacement gas-fired boiler installations were required to be condensing boilers of at least 86% efficiency (SEDBUK Band A or B).

"Over the years, the development of boiler technology has seen efficiency levels grow massively and now that Part L of the Building Regulations is now firmly in place for gas-fired appliances, manufacturers are keen to prove their boilers are amongst the most efficient.

"A high efficiency condensing boiler works on the principle of recovering as much as possible of the waste heat which is normally rejected to the atmosphere from the flue of a standard efficiency (non-condensing) boiler.

The best high efficiency condensing boilers convert more than 90% of their fuel into heat, compared to 78% for conventional types.

"This is accomplished by using a larger heat exchanger or sometimes two heat exchangers within the boiler which maximize the heat transfer from the burner as well as recovering useful heat which would normally be lost with the flue gases.

When in condensing mode the flue gases give up their 'latent heat' which is then recovered by the heat exchanger within the boiler.

As a result the temperature of the gases exiting the flue of a condensing boiler is typically 50-60degC compared with 120-180degC in a current non-condensing boiler.

At the same time an amount of water or 'condensate' is produced.

"There has been some talk in recent months of the 100% efficiency boiler, however in actual terms this will never be physically possible using current technology.

The highest achievable efficiency for gas-fired boilers is currently 91.6% and I don't see us being able to go much beyond that in the future.

"The real opportunity in terms of increasing efficiency with home heating and hot water provision is to look at secondary efficiency which can be affected by factors such as electricity consumption, standby losses, advanced controls and power save functions.

"At Worcester we are currently appraising a number of options in terms of extra components which will potentially improve these secondary efficiency levels in our Greenstar boilers.

"Other key factors which will also help a boiler run more efficiently include the correct pipework sizing, siting the boiler in the most suitable location and regularly flushing the system, helping to prevent corrosion and make sure it's free from debris.

"Over time your heating system can become rusted from the inside producing iron oxides (black sludge).

This sludge plays havoc with the working parts of a heating system, blocking pipes, radiators, valves, pumps and heat exchangers.

If left to corrode for too long this can significantly reduce the efficiency and even cause premature failure of any of these components.

"The overall carbon savings can be huge if homeowners take a little time out to think about their central heating system operation and installers have a big part to play in encouraging their customers to do this.

They have the direct contact with end-users and this is the best opportunity to convince them they can make a big difference with their actions.

Not just for the environment either; the financial benefits are significant too.

Research from the Energy Saving Trust (EST) claims that potential savings on heating bills can work out around GBP200 a year by replacing an old standard efficiency boiler with an A rated appliance, and combining that with well suited controls.

"Controls can significantly improve the efficiency of the heating system, but selecting the right unit is paramount.

Weather-compensation, for instance, is widely specified in Europe yet infrequently at present in the UK - even though it improves efficiency by reacting to actual weather conditions rather than flow and return water temperatures.

"Controls also have a vital role to play in adjusting a boilers firing rate (input) to meet the heating demand (output) of the system.

By modulating input correctly, less fuel is burned and wasted and emissions are reduced in the process.

"Recent technological advances mean a wide range of intelligent options are now available for installers to choose from in order to meet the exact requirements of each individual household they visit.

Whether specifying basic controls, like mechanical timers, or opting for more advanced controls with room thermostats, such as radio frequency or weather and load compensation systems, it is important to specify the most compatible product in order to ensure best performance from a high-efficiency boiler.

"Combining a high efficiency condensing boiler with our Greenskies solar water heating package will also improve a home's efficiency with 50 -- 70% of a home's hot water provision being provided for free by the sun.

Not only will this represent a further cost saving on bills, it will further reduce the CO2 emissions from the household as the majority of the time you turn on the hot water during the year the boiler will not need to burn any fuel, the heat will be provided by the solar panels.

"According to the EST if everyone in the UK with gas central heating installed a high efficiency condensing boiler, we would save enough energy to heat 3.7 million homes for a year.

So we don't need 100% efficiency boilers, we just need more people to re-think their current heating system.".
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