What Type of Heating System?

Modern boilers are highly efficient and sophisticated systems. Since the old oil burning boilers from decades ago, the boiler manufacturers have gone a long way to make quieter, more robust, cleaner and even cheaper boilers. Plumbers these days install modern heating systems that are highly sophisticated, with new systems adopting wireless radio frequency room thermostat and digital controllers to create a pleasant environment that can be different in each room in the house.

There are various types of boilers and within them there are many different boiler manufactures with differing features. In this introduction our plumbers introduce the major types of central heating systems and their key components starting with boilers and their various features to match your individual needs for space heating and domestic water heating.

In order to address the various types of heating systems in the UK, the boilers are normally grouped into three main groups:

  • Combination (Combi) boilers
  • Regular boilers (also referred to as ‘traditional’ or ‘conventional’ boilers)
  • System boilers

Combination (Combi) Boilers
Most plumbers at the moment are very supportive of Combi boilers. The combination (Combi) boiler is a very effective instant water heating solution, and is proving to be a huge success in the UK, with new plumbers converting to this technology by the day. It is saving space and is neatly designed to make it very attractive. Combi boilers actually account for over half of the new domestic boilers installed in the UK annually, with most plumbers having been trained to install one of them.

Combi boilers differ from other boilers in that they do not need to store the hot water, thus eliminating the need for hot water storage tanks (normally positioned in the airing cupboard). Combi boilers combine (hence the name) water heating and central heating system boiler capacity in a very efficient fashion within a small compact unit which is normally mounted in the kitchen (or the airing cupboard in some cases).

Because there is no need for a large hot water storage tank, there is a major space saving benefit and the ease of installation is attractive for plumbers. This is further reinforced by the fact that the combi boiler operates without header tank in the loft. Unlike in traditional heating systems (vented heating systems) which include components such as cold water storage cistern or other tanks in the loft, the Combi boiler in a self contained unit that takes only little space.

There are additional benefits on actual cost of water heating, and the fact that the hot water is running through the taps (and shower) at mains pressure. In many conventional (vented) system, where the height difference is small between the header tank in the loft and shower, the water pressure is very disappointing, due to low head column. Many plumbers have pointed out the high water pressure from the Combi boiler as a major advantage.

Other cost savings associated with the Combi boiler stem from the ease of installation. As there are no piping connections to a header tank in the loft, or a hot water storage tank in the airing cupboard, experienced plumbers and heating engineers confirm that it leads to significantly shorter installation time and lower installation costs.

System Boilers
System boilers are another staple of UK heating market with many plumbers have massive experience in installing and servicing them. The boilers rely on stored hot water in a special cylinder (unlike the Combi boilers). This is true both for System boilers and for Regular (Conventional) boilers.

System boilers have two key differences between them and Regular (Conventional) boilers:

  • In System boilers, many of the individual components of the heating and hot water system are built in, which means that the installation is quicker, simpler, and cheaper, a major benefit for plumbers and heating engineers.
  • The hot water is pumped from the boiler through the system to the radiators and hot water cylinder, making the system quicker in response time and more economic to run.

Regular (Conventional) Boilers
In most cases with an old central heating system in place, there is a good chance that the system is with a Regular boiler. A typical conventional system includes a boiler with the controls, a feed and expansion cisterns (normally in the loft), a hot water storage cylinder (normally in the airing cupboard). The boiler is fed by a cold water storage header tank in the loft.

High Efficiency Condensing Boilers
High efficiency condensing boilers are considered to be the most efficient fossil fuel boilers, offering both excellent heating performance and very good economy. Most certified plumbers these days deal primarily with such boilers.

They are called ‘condensing’ boilers due to the condensation of water inside the boiler or the flue system. This condensation is a natural result of combustion taking place inside the boiler. This condensation is a result of the boiler process of extracting extra heat from gases that would normally be expelled to the environment.

High efficiency boilers have to meet strict requirement of at least 86% efficiency. This means that at least 86% of the gas used to fire the boiler is actually converted into useable energy such as space and water heating. In other words, only a small percentage (in this case less than 14%) is expelled as waste. This rate should be compared to old boilers that are currently operating around the country reaching efficiency levels of around 50%. Even new models that are not of the ‘condensing’ type reach levels not exceeding 70-75% efficiency.

Due to such high efficiency, condensing boilers can make a major impact on your heating bill. Installing a high efficiency A-rated condensing boiler (A rated will have efficiency rating of over 90%) will reduce your heating bills by about 35%.

High efficiency condensing boilers, that can be installed by most qualified plumbers are offered by many manufacturers in the UK with various features and sizes. There are high efficiency condensing boilers that can burn gas, LPG and oil as their fuel.

Condensing boilers achieve this high efficiency by effectively reclaiming heat that would otherwise be lost through the plumber installed flue to the environment. The boiler reclaims this heat by a larger or a second heat exchanger. This reclaimed heat is also beneficial in terms of reduced carbon dioxide emissions, by substantially reducing the emissions of greenhouse gases into the atmosphere and helping the war on climate change.

The Right Boiler for the Job
The following table, which was developed with experienced plumbers, shows a few typical scenarios and the type of boiler that is most appropriate for them. However, it is highly recommended to discuss your specific situation with an expert plumber or heating engineer from our network to help and design the perfect combination of boiler and heating systems for your specific needs  

Combi Boiler   

  • Loft space is important, you would like to free up space for storage or loft conversion
  • Your property is small, you live in a flat, space is at a premium
  • You do not have a loft and are looking to replace your boiler
  • You already have an old Combi boiler and you are looking to replace it
  • You are looking for a small boiler to fit in the kitchen

System / Conventional Boiler   

  • Your property has 2 or more bathrooms
  • The mains pressure in your property is low
  • You have an old gravity fed system that requires a new boiler
  • There is a large demand for hot water in your household
  • You have a large house with 5 or more bedrooms and 2 or more bathrooms

Importance of Heating Controls
Installing a brand new high efficiency boiler is only going to pay dividends if it is coupled with effective controls. They will ensure that the heating system in general and the boiler in particular are efficiently utilised and savings are extracted as designed.

These days there is a wide range of heating controls to suit every taste and purse. There are simple mechanical devices and sophisticated digital and wireless radio frequency programmers available on the market. However the key issues is the ensure that the heating system is installed by a professional plumber and is married to the right control system, to guarantee efficient and economic operation.

The heating controls allow you to set a pleasant and economic heating set up. For example by reducing the room thermostat by 10c from 21c to 20c, you could save your energy spend on heating by up to 10%. Furthermore, by installing sophisticated controls you can tell the heating system precisely what temperature you would like to have in each room in the house. For example you can set the living room to be warm, while the bedroom to be cooler. Also you can set the heating to turn on and off at specific times, thus eliminating wasteful heating when you are away from home.

New building regulations that came into effect in April 2005 define very clearly what is expected of the controls of a heating system. For example, for a Combi boiler powered central heating system, the controls should include: a room thermostat, timer/programmer and thermostatic radiator valves (TRV) on all radiators on new systems (except for the room with the room thermostat). When a boiler is replaced, thermostatic radiator valves are required at least for the bedroom but recommended on all other radiators as well. For a System or Conventional boiler, the requirements are similar, except that the system must be fully pumped and instead of a timer, there should be a full programmer to enable the heating and hot water operations to be programmed separately.

Radiators are heat exchangers designed to transfer thermal energy from the boiler to the room by ‘radiating’ the heat into the room environment. A typical radiator is made of sealed, normally flat, metal container, which houses the water pumped by the heating system. Air surrounding the radiator heats up, and rises to the top of the room, drawing in cooler air to heat up and continue this cycle.

There are three key components attached to a typical radiator: manual air release vent, lockshield radiator valve and a manual (or thermostatic) radiator valve.

Manual Air Release Vent
If there is air trapped inside the radiator, it can escape via the manual air release vent. In order to operate effectively, a radiator must be free of any air. This can achieved by turning the vent with a special key to release any air locked inside the radiator.

Lockshield Radiator Valve
Lockshield radiator valve is used to balance the radiator to heat up evenly across the whole area of the radiator. Normally the adjustment is carried out by the heating engineer upon installation.

The setting is typically reflecting a 10-12c difference between the incoming flow of hot water and the outgoing flow. This difference can rise to 20c for condensing boilers.

Thermostatic Radiator Valve (TRV)
Most modern radiators come with a TRV, which lets you control the temperature on an individual level in each room. The thermostatic radiator valve typically has a range of temperatures up to 22c. 

For proper operation of the TRV, it is important to ensure it is not obstructed by curtains or furniture, to allow it to read the room temperature accurately, and ensure it shuts the radiator down if the room has reached the preset temperature to conserve energy and cost.


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