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Heating controls Heating controls
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Central heating systems

We install and maintain natural gas, oil and LPG central heating systems. Any two central heating systems are never normally exactly the same as variations in system design can vary dramatically from system to system. Considerations such as the number of radiators, number of bathrooms and lifestyles of occupants can play a major part in your central heating system design. Your central heating system needs to be carefully planned and executed.









On this page you will find information on the types of central heating systems available, the variations and differences with natural gas, oil or LPG fuel and pipework considerations. For central heating systems that feature water cylinders please visit our water cylinders section of this website for more information. We are Gas Safe and Oftec registered and are well trained to deal with any of your gas or oil central heating enquiries.

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Types of central heating systems



conventional central heating system

conventional boiler

Conventional system (open vented)

A conventional system would normally consist of boiler, pumped pipework system, a feed and expansion system, and a hot water cylinder (usually in the airing cupboard) fed by a cold water storage tank normally located in the loft.


This system usually requires two cold water storage tanks, one for the central heating and other other to feed the hot water via the cylinder.


This system is normally found in an older house and is often suited systems that require a great deal of water, but can be expensive to run.



System boiler central heating

system boiler

System boiler (pressurised system)

A system boiler is available as an unvented high pressure system (top picture) and a open vented low pressure system (bottom picture). Unlike a conventional system a system boiler does not require a cold water storage tank for central heating requirements as the system boiler includes an expansion vessel, pump and other components. Also the hot water supply is pumped through the system and radiators.


In an unvented system boiler there is no requirement for a feed and expansion tank. Within the boiler there is also a pressure relief valve and a pressure gauge which allow the necessary to form a sealed system. A system boiler would be a suitable choose if you wanted independent water and heating which would then combine with an unvented cylinder.


Combination boiler system

combi boiler

Combination boiler system (sealed system)

A system designed with a combination boiler means that your boiler will provide hot water for all of your heating requirements. This is a big space saver as you do not need a hot water storage tank and other associated components. Benefits include more space, reduced water costs and you can enjoy hot water at mains pressure.


Before a combination boiler is installed into your home your mains water supply needs to be tested to check for sufficient pressure. A combination boiler may not be suitable if your home has a number of bathrooms and hot water requirements are high as the combi boiler may be unable to keep up with demand.



These systems can be further separated into different system variations or 'buzz words' such as a fully pumped system, fully pumped sealed system, gravity fed hot water pumped system and a central heating with an unvented storage system.

  • Fully pumped system - This is a term given to system that uses a pump to move all of the heat from the boiler to every part of the system. Usually only one pump is used to circulate all of the hot water needs. Under Building Regulations this is now a requirement for all new and retro- fitted central heating systems. This system can give the user a lot of control on how the heat is distributed. Fully pumped systems are usually associated with conventional systems or system boiler.
  • Fully pumped sealed system (unvented)- A sealed system means the hot water produced from the boiler, which then circulates around the radiators is held within a closed circuit under pressure. As the system is sealed it reduced the chances of sludge, airlocks and corrosion. Fully pumped systems are usually associated with the system boiler design, although combination boilers are also a sealed system but not fully pumped.
  • Gravity fed hot water pumped system - This system is similar to that of the fully pumped system apart from the pump is not called upon to move all of the heat throughout the system all of the time. A gravity fed system using gravity to move the domestic hot water to the cylinder. As cold water is heavier than hot water, as the boiler creates hot water it pushes the cold water down and forces the hot water up into the cylinder. Should the room thermostat call for heating whilst the hot period is on, the pump simply switches on to supply the central heating requirements. This system is reliable but may prove expensive to run and is mostly associated with a conventional system type.
  • Open vented system- In this type of system there is an expansion tank fitted high up, (usually fitted in the loft next to the header tank) which feeds the water down the 'cold feed' into the central heating system. The flow rate and pressure of the hot water discharged from the hot water outlets is then dependent on the height of the storage cistern above the outlets. This system is associated with a conventional system. The expansion tank and storage cistern can be replaced with an un-vented cylinder which is water mains fed that can also greatly improve upon this older style system.

Oil, LPG or Natural gas?



oil central heating


Oil based central heating systems are usually like for like more efficient than their gas counterparts. With oil based systems you are usually more restricted when choosing your boiler, however you do not need to sacrifice on quality. The main difference in an oil central heating system is that you will need an outside oil tank to house your oil requirements. You must also keep a careful check on your oil level.



LPG central heating


Liquid petroleum gas is another alternative to mains gas, where perhaps main gas may be too expensive or impractical to use. LPG is much the same as natural gas concerning a central heating system. However you will require to keep cylinders outside of your house to supply your LPG requirements (supplied by Calor). You would usually require two cylinders with a valve switching between the two. Your boiler must also be LPG compatible either by buying a new boiler or converting your present boiler to accept LPG (if applicable).





gas central heating

Natural gas

This is by far the most common fuel type and is piped to your home via a supply company. If you require natural gas but your home is currently not connected to a supply it may prove expensive to get connected. You will need to contact Transco to arrange for the supply to be piped to your home and also arrange with a gas supplier such as British Gas to install a gas meter. A natural gas supply is perhaps the most convenient fuel with the added benefit of knowing that you will not have to worry about your gas supply needing topping up.



Another important part of your central heating system is your associated pipework which will connect your boiler to all the other components, such as your radiators, cylinder (where applicable), showers, taps, etc. Given this the pipes in a central heating system plays an important role in your entire system and should always be planned out carefully.


Pipework considerations

  • If your pipes / radiators are dirty they will need power flushing
  • If a new boiler is to be fitted to an old system, a power flush will always be required.
  • Is you present pipework the correct diameter, too big will cause low pressure and too small may increase pressure too much and may cause other detrimental effects.
  • Where do you want your radiators, how will the pipework get to the desired location?
  • Is your present pipework in a sound condition, are there any leaks, rust or other problem areas?
  • Do you want to try and hide as many pipes as possible?
pipework considerations


What we can offer


If you require a central heating installation you will normally require a survey from our technical surveyor. Most central heating installations will normally include a boiler installation, therefore please refer to our boiler installation guide for more information regarding our service.


We install maintain and repair all aspects of a central heating system from the boiler right down to a radiator valve. We offer upgrade solutions for your old boilers, new efficient systems for new installations and replacement parts such as fittings TRV's, pumps and cylinder replacements. All of our work is guaranteed and carried out to our usual high standard.

Please contact us to discuss your requirements:Corgi, Oftec and Energy Efficiency


TG Services

1 Wintershill Farm

Wintershill Estate

Durley, Southampton

SO32 2AH

Tel: 02380 000701



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