Choosing a Boiler can be quite daunting and you may need the advice and expertise of a Gas Certified Engineer. However, we have included relevant information in this section, to aid you in your decision making.
Legislation – Boiler Installation
Since October 2010, building regulations require all newly installed boilers to be at least 88% efficient (SAP 2009). Hence, legislation effectively permits only energy efficient Condensing Boilers to be installed as new or replacement units.
SAP (Standard Assessment Procedure) has replaced SEDBUK 2005. SEDBUK was introduced as a simple guide to identify and compare the energy performance and efficiency of different boilers. SEDBUK 2005 efficiencies were expressed as a percentage on an A to G scale.
This SEDBUK band rating has been withdrawn to avoid confusion with the proposed European energy label using similar ratings. The table below appears here because the SEDBUK A-G ratings still continue to be commonly quoted.
SAP 2009 (also referred to as SEDBUK 2009) is the Government’s methodology for calculating the energy performance of dwellings, and it now provides the best available estimates of annual average efficiencies of boilers when installed in typical domestic conditions on the UK.
In the SAP efficiency assessments, the original SEDBUK A-G grouping has been replaced with simple performance percentages. To qualify for the Energy Saving Trust Product Endorsement Scheme gas boilers must have an efficiency of at least 90%.
Determining Boiler Efficiency
For more information, or to check out the efficiency of your own boiler visit www.boilers.org.uk
What is a Condensing Boiler?
A Condensing Boiler works like a Conventional Boiler in that fuel is burnt to heat water in a heat exchanger. The main difference is that an energy efficient Condensing Boiler has an oversized heat exchanger/s to maximize heat transfer from the burner and hot waste flue gases. Essentially, a condensing boiler takes back some of the heat from these waste flue gases, so much so that the temperature of the exhaust flue from a Condensing Boiler is between 50-60 Celcius compared to 120-180 Celcius from a Conventional Boiler. As such, Condensing Boilers are much more efficient, more economical to run and more environmentally friendly.
The drawback of Condensing Boilers is that they produce an acidic liquid in the condensation process, which makes it a necessity for the condensate to be plumbed into a suitable drain, and for the heat exchanger/s to be constructed from non-ferrous metals to minimize corrosion.
The benefit of Condensing Boilers is their efficiency. A typical old non-condensing boiler converts just 60% of its fuel into heat, whilst the efficiency rate of a modern condensing boiler can be up to 90% or above.
A boiler with an efficiency of 60% wastes £40 for every £100 spent in heating, whereas with a modern condensing boiler with an efficiency of 90% only £10 of a £100 bill is wasted.
Only boilers with an efficiency of 90% or above carry the Energy Saving Recommended logo.
Energy efficient condensing boilers can be easily fitted to most new and old heating systems. If your boiler is old and inefficient, fitting a new energy efficient boiler with a full set of heating controls can reduce your fuel costs by up to a third.
Types of Condensing Boiler
There are basically three (3) types of energy efficient condensing boilers namely, Combination Boilers (Combi Boilers), Regular Boilers and System Boilers (the latter two often referred to as Heat Only Systems). Each is best suited to different types of home and your GAS SAFE REGISTERED engineer should be able to advise you as to which will best meet your needs.
- Combi Boilers provide heat and instant water without the need of a water tank. Cold water from the mains is heated as it passes through the boiler straight to the taps. Because of their efficiency and space saving features, Combi Boilers account for over 50% of all new domestic gas boilers installed in the UK annually. They are ideal for one-bathroom homes which do not have heavy hot water demands, and are easy to install. However, hot water flow can be low because the cold water has to regulated within the boiler so that it can be adequately heated before going to the taps.
- Regular Boilers work on the principle of stored water in a tank. The size of the tank determines how many bathrooms can be provided with hot water. These boilers take up more space and are more costly to install as they usually require a feed & expansion tank in the loft, a hot water cylinder (often stored in an airing cupboard), and the boiler which is commonly located in the kitchen. Faults are easier to detect due to the separate units, but they can be a problem to install in flats or houses/bungalows where the loft space is fully utilized for living.
- System Boilers are similar to Regular Boilers but contain most components within the boiler casing.
Maintaining Optimum Boiler Efficiency
Condensing boilers are so named because they condense periodically. They extract heat from the exhaust gases which would otherwise be lost through the flue – turning water vapour from the gas into a liquid water condensate.
Whilst a condensing boiler is always more efficient than a non-condensing boiler due to its larger and more efficient heat exchanger, it operates still more efficiently whilst it is in condensing mode.
Although a condensing boiler does not always operate in condensing mode, there are steps that you can take to increase operation in condensing mode.
- Try to ensure that the water returns to the boiler at just the right temperature to encourage condensing. Ideally returning water temperature should be in the 50s degrees centigrade.
Having slightly oversized radiators increases the efficiency a little because the circulating water loses more heat whilst moving around your system, so it returns to the boiler at a lower temperature, encouraging condensation.
Having larger radiators also means that you can operate your heating system at lower temperatures, again encouraging condensation.
It is not economically beneficial to change your radiators to obtain this small gain, but if you have installed good insulation since having your central heating system installed (such as double glazing), your radiators are likely to be a little oversized as a result.
- Fit an outdoor ‘weather compensator’. Such a sensor takes account of outside temperatures, and enables the boiler to determine the minimum heat it needs to meet demands. Being able to operate at lower temperatures, means it can remain in condensing mode for much of the time it is operating.
Should I Upgrade my Boiler?
You should consider upgrading your boiler if it is an old inefficient boiler of more than ten (10) years. Boilers that are 10-15 years old or more are only about 60% efficient or less. This means for every £1 spent on fuel for a boiler with an efficiency of 60%, 40p will be wasted. In contrast, modern condensing boilers are the most efficient available today, and boilers of this type typically have an energy efficiency rating of up to 95%.
Check and compare the efficiency of different boilers by viewing the SAP (Standard Assessment Procedure) Boiler Efficiency Database at www.boilers.org.uk
Which Boiler Meets My Needs?
Once you have ascertained that it would be more cost effective to upgrade/change your old boiler, you should discuss this with your Gas Safe Registered Engineer who will be able to advise and guide you in your decision making process. However, please see our section ‘Types of Condensing Boilers’ which gives a brief introduction to the three types of boiler available to you.
In addition, to boiler type, you will need to consider boiler size. Oversized regular boilers cost more to purchase, and generally operate less efficiently, resulting in higher running costs and increased greenhouse gas emissions.
Most boilers come in a range of sizes (typically 12-40kW) suitable for different homes. Factors that go into boiler size calculations include the size of the home, the usage of hot water, the number of bathrooms and radiators, presence of insulation and ceiling height.
Alco Gas Care has a wealth of information and experience, so we can recommend not only type / size of boiler, but relevant brands and models, bearing in mind other key considerations such as their reliability and ease of use.
Just one of our testimonials…
My daughter recommended Denis to me when I had a problem with my boiler which was causing the hot water to run cold. He quickly found the problem, sourced the new part needed and fixed the boiler within 2 hours. Excellent value for money and very professional.
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