Basic Guide To Central Heating Systems

Basic Guide To Central Heating Systems2018-10-16T15:24:00+01:00
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Introduction to Central Heating Systems

Your central heating system provides your essential heating and hot water, so ensuring that it is properly installed, serviced and maintained is imperative.

A central heating system, as the name suggests, provides heating from one central source. The most popular form of central heating is a ‘wet system’ which is powered by a gas boiler connected to a system of radiators and in some cases a hot tank of water.

The key component of any central heating system is the boiler. Essentially there are 3 main types of high-efficiency condensing boiler and each type is suitable for different types of homes and usage requirements. When choosing a boiler for your central heating system it is wise to have a grasp of the basic differences between the different type of boiler systems.

A central heating system, as the name suggests, is a means of providing warmth and hot water for your home powered by one central source. Central heating systems broadly fall into one of the following types:

  • ‘Wet systems’ with a boiler and radiators
  • Warm air system
  • Storage heaters

‘Wet systems’ are the most popular form of central heating system in the UK, most of which are fuelled by natural gas. Electric central heating boilers are also on the increase, as they are ideal for properties without a gas connection such as flats and apartment blocks. Other systems are fuelled by heating oil, occasionally liquid petroleum gas (LPG), and though rare, coal pellets or biomass such as wood chips.

In a typical ‘wet system’ a gas boiler is used to heat the water circulated through the network of pipes and connected to the radiators throughout the house. Additionally the boiler is usually connected to a hot water cylinder or tank which supplies the hot water for showering and washing.

The radiators, despite their name, do not simply radiate heat, but deliver most of their heat through convection. Essentially, the air warmed by the radiator naturally rises, and cool air takes its place. The resulting process means that as the warm air circulates the room is temperature is increased.

New gas (and oil) boilers generally use condensing technology and need to have and A or B energy rating, which equates to around 90% efficiency or higher. If your boiler is over 15 years old, you may wish to consider upgrading to a new energy-efficient boiler system.

What Are The Benefits Of A Gas Central Heating System?

Our guide to central heating is designed to give you an essential understanding of the options available to you when having a central heating installation. We should point out that this guide is intended to give you a reasonable understanding of central heating systems. In the interests of your own safety we always recommend seeking the advice of a qualified, Gas Safe Registered plumbing and heating engineer with experience of different heating systems, to make sure that your new heating system is designed to be practical and efficient for both your property and usage requirements.

Assessing your home heating

All Plumbing Wise heating engineers are suitably trained and experienced in assessing a property requiring a gas central heating installation. We welcome the opportunity to provide you with free impartial advice on the best boiler type and size, and central heating installation configuration for your property and usage requirements. All our estimates are free of charge and will be provided to you in a quick and easy to read format.

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020 8362 1389

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A Brief Guide To The 3 Types of Boilers

heating-with-combination-boiler-systemCombination, or ‘combi’ boiler systems are becoming increasingly popular within the UK as they remove the need for independent tanks, pumps and valves; as these are built in within the boiler. Combination boilers heat your home and provide instant hot water as and when it is needed. The benefit of the combi boiler system is that everything is self-contained, thus reducing the space it takes up and the heating parts that may need servicing and repairs. However, combi boiler powered central heating systems do not have a hot water tank facility, so should the boiler ever breakdown, there will not be a reserve of stored hot water available. If a combination boiler system is installed in an unsuitable type of property (ie one with 2 or more bathrooms), this can lead to pressure problems when numerous systems using heated water are run simultaneously.

heating-with-open-vent-boiler-systemConventional boiler systems tend to be found in older properties. These gas central heating systems normally comprise of a heat only boiler, a copper cylinder which stores the hot water, a cold water storage tank and a Feed and Expansion tank. In a typical gas central heating system installation the mains water supply will feed into both of these tanks and the kitchen sink cold tap, and usually no more. The advantage of conventional boiler system is that they maintain a good pressure and do not suffer the pressure drops that combination boiler powered heating systems can sometimes experience. This is because the heated water is stored in a tank. One of the disadvantages of the conventional boiler and heating systems are the amount of space required to accommodate all the parts of the system; which can be quite extensive. Running costs for these systems can be relatively large and uneconomical, particularly for large properties or for only a one person household.

Central heating with a system boilerThe System boiler set up is quite similar to that of a conventional boiler, but usually the hot water cylinder is an Unvented Cylinder (for example, a Megaflow) which means that there are no cold water storage tanks or feed and expansion tanks. The hot water cylinder is mains fed so the pressure at the hot tap will be similar to the mains water cold feed entering the property. The advantages of system boiler systems are; the space savings that can be achieved by not having the tanks and the greater flow rate at the hot tap. The hot water cylinders can also be stored in garages and attics. On the flip-side, the disadvantage of a system boiler set-up can be the cost of them and the minimum requirement of a mains water flow rate of 22 litres per minute.

Please visit our Choosing a boiler page for in-depth information on boilers and installations.

Gas Rates & Boiler Connections

In order to meet gas regulations and manufacturers’ warranty requirements it is imperative that the gas supply to your boiler is sufficient.

This is not always determinable if the existing boiler is not currently working and so therefore it might be necessary for your gas supply to be upgraded. As a general rule, if there is a 22mm gas supply to your boiler and the gas meter is not too far away then the supply should be good enough. However, if the supply of gas is insufficient, the following charges for re-running a gas line will apply. (Please note that these will ordinarily be included within the Fixed Quote that is provided, unless it is actually not possible to trace the gas supply from the meter to the boiler).

Gas Line Length


0-2m Free of charge
2-4m £50.00
4-6m £100.00
6-10m £165.00


Preparing The Heating System

Magnetite or sludge is made up of a combination of dirt, mites and corroded metals and can be found within any part of your central heating system. It not only creates cold spots within your radiators, left untreated it can also create blockages, but more concerning, as it is corrosive, may well rot new aluminum heat exchanges that are common place within modern boilers. This is why at Plumbing Wise, we recommend one or both of the following:

  • Installation of a Magnaclean – a magnetic device that attracts and filters magnetite before it enters the boiler.
  • A complete Powerflush of the system. Using cleaning chemicals and neutralizing crystals. This aims to rid your existing system of sludge, thus extending the life of your new boiler and meeting manufacturers’ warranties.

As mentioned these are both optional, but are highly recommended.

Condense Lines

All newly installed boilers now have to be of the Condensing type, as they are the most efficient boilers available and recover much of the waste heat that would escape from the flue of a conventional boiler.

The by-product of this is in an acidic water form and has to be taken away from the boiler to a drain or a soakway. Ideally, we will try to terminate this condense line to position internally within the property. However, this is not always possible and so sometimes will have to be run externally.

When this is the case, we will ensure that the condense pipe is properly lagged, securely clipped and run in 22mm Condense Line for no more than 2 metres. Longer runs will be increased in size to 1’ ¼” waste pipe. This will ensure no freezing of the condense line pipework which is becoming so prevalent of recent years.

Choosing A Boiler

One of the top priorities is to identify which type and size of boiler is best suited to your needs. Calculating the size is absolutely essential and should be considerate of variables such as size of the property and its rooms, orientation (btu requirements), materials, insulation and flow rate (for Combi’s).

Our Choosing a boiler page will give you further advice on the options available.

Call us on:
020 8362 1389

Email Us:
Send a message via the Contact Us page

Choosing an energy efficient boiler