Heating Systems

Domestic oil heating systems

A wide range of oil heating and cooking appliances are available for domestic use. This guide describes the different types of appliances that are available and outlines the basic principles governing their use.

Appliance types

Designed to be strong and long lasting, oil fired appliances are some of the most efficient you can get. There’s a huge choice of floor standing or wall mounted boilers for installation inside and outside domestic premises. Regular boilers are designed to heat water within a heat exchanger by absorbing the heat contained in the flue gases created by the burner. Sealed system boilers include a circulating pump, expansion vessel and other components needed for a “sealed system” and don’t need an expansion cistern in the loft space.

Both regular and sealed system boilers require a separate hot water tank. By contrast, combination boilers are capable of providing hot water on demand, as well as heating. They can save space because no hot water storage cylinder is required. However, sufficient water supply pressures and flow rates are required for optimum performance.

Oil range cookers have been available for many years. Some models have integral boilers making them capable of providing central heating and hot water too. Room heaters or stoves are available with decorative effect fires burning oil through imitation coals behind a glass front. Some of these will have back boilers capable of providing hot water and/or a central heating service.

Your OFTEC registered technician will be able to offer advice on the type of appliance which best suits your needs.

Appliance efficiency

Older oil boilers are typically around 60-70% efficient. Modern high efficiency condensing boilers are normally more than 90% efficient and are available as regular, system and combination boilers. Installing a condensing boiler is an excellent way to reduce running costs compared with non-condensing boilers and a fuel saving of up to 30% can be expected. In all regions, condensing boilers are now the preferred method of meeting building regulations. However, non-condensing boilers can be fitted if the building qualifies for an exemption. Exemptions are based upon the outcome of an assessment into the technical difficulty and cost associated with installing a condensing model.

Appliance location

When deciding upon a location for an appliance, provisions for system pipework, oil supply pipework, electrical connections, flue terminating positions and ventilation must be taken into consideration. Open flued appliances draw air for combustion from the room in which they are fitted. They should not be fitted within, or draw air from, a bedroom or bathroom. Modern condensing appliances will emit plume (water vapour) from the flue on cold days. Extra care needs to be taken when siting a condensing flue to avoid the plume causing nuisance to you or your neighbours. Garages are often used for siting oil fired appliances. To prevent car fumes being drawn into the boiler, a room-sealed balanced flued appliance should be used as fresh air for combustion is taken directly from outside via the flue system. Some oil fired boilers are designed to be installed externally. Others are available that can be installed “through the wall” minimising their impact if internal space is at a premium. Your OFTEC registered technician will be able to offer advice on your options for a suitable appliance and its location.

Maintenance and safety

Oil boilers have an excellent safety record. However, it’s worth fitting an audible carbon monoxide alarm as a precaution, particularly when open flued appliances are used. Oil fired appliances should be serviced at least annually or in accordance with the manufacturers instruction and it is important that service access is provided. Appliances should not be placed where a ladder is needed for maintenance.

Systems and controls

Modern high efficiency condensing appliances require fully pumped systems, which use an electric pump to circulate the heated water around your heating system. If you have an old heating system or perhaps one which doesn’t use a pump to circulate the water, it must be upgraded to a fully pumped system when the appliance is replaced. Accurate system controls can help you save money by reducing heat wastage. By reducing room temperature by 1ºC, you can save up to 10% off your annual fuel bill.

Minimum system controls should include:

  • Room thermostats
  • Thermostatic Radiator Valves (TRV’s)
  • Cylinder thermostat
  • Programmers to set ‘on and off’ time periods
    There is a vast selection of modern controls available to achieve compliance with building regulations and increase energy efficiency. Your OFTEC registered technician will be able to advise you on which controls will best suit your system and lifestyle.

    Annual inspection

    All oil appliance installations should be serviced at least annually to ensure safety and correct operation. The annual service should include checking the oil tank and associated pipework.

  • Domestic oil supply pipes

    Oil supply pipes are a vital part of any oil heating system and it is important that they are installed and maintained correctly to ensure system reliability and safely. Correct installation also helps to avoid the risk of leaks, which can cause pollution and are costly to clean up. This guide applies to pipes that carry fuel to oil fired appliances of up to 45kW output which are located in properties used primarily for domestic purposes.

    Oil feed pipes

    Domestic oil supply pipes are usually made of plastic-coated soft copper tubing that can be easily manipulated. Steel pipes are not commonly used for domestic installations, but steel pipes can offer additional protection from damage or vandalism. If steel pipes are used, they should not be galvanised and must be painted and maintained to minimise corrosion. Plastic pipe systems are also available but must only be used below ground. Fittings and jointing materials must be suitable for the type of pipe and fuel being used.

    Oil supply systems

    There are two types of oil supply systems; gravity and sub-gravity. Gravity supply systems are arranged so that the pressure of the oil in the tank pushes the oil along the pipe to feed the burner at the appliance. A typical gravity supply would consist of a bottom outlet oil storage tank positioned above the height of the burner.

    The tank is often elevated to the required height by a platform on top of brick piers.

    Sub-gravity systems rely on a mechanical device such as an oil de-aerator or lifter to assist the oil in reaching the burner. For satisfactory performance, it is critical that oil supply pipes used with sub-gravity systems are correctly sized.

    Your OFTEC registered technician will be able to suggest the most appropriate oil supply system for your particular needs.

    External/exposed pipes

    For best performance, oil supply pipework should take the most direct route between the oil tank and burner, while avoiding high and low points in the pipework, the creation of trip hazards, or anything likely to damage the pipe and joints. Pipes must be supported by purpose made clips and attached to permanent structures such as a wall. A garden shed or wooden boundary fence is not classed as a permanent structure because it will deteriorate with age and any movement may damage the pipe and fittings.

    Buried oil supply pipes

    Directly buried oil supply pipes should be protected against the risk of accidental damage caused by digging. The recommended installation method is as follows:

  • A trench should be excavated to a depth of 450mm
  • 40mm of compacted sand is laid on the bottom of the trench, the oil pipe positioned, and a further 40mm of compacted sand is laid above the pipe
  • Builder’s grade polyethylene is laid above the sand and the trench is then backfilled, positioning an oil line warning marker tape 150mm below the finished ground level.
    Oil supply pipes should be buried at least 300mm clear of other underground services such as water and electricity. Joints in buried pipework should be avoided if at all possible. If joints have to be made, a permanent means of access for inspection of the joints must be provided.

    Entry into buildings

    Where an oil pipe passes through the wall of a building it must be run within a sleeve, such as a larger plastic pipe. Oil supply pipes should not be run underground directly into the interior of a building. Instead the pipe should rise externally to allow a remote acting fire valve to be fitted before it enters the building.

    Fire valves

    A fire valve is an essential safety feature of an oil installation, which will stop the supply of oil in the event of a fire or an overheat situation occurring at the appliance. The valve must be located outside the building, before the point of entry, and must be activated by a remote sensor. Existing oil feed pipes that are not accessible outside of the building, and do not have a fire valve, can have one added at the first point where the pipe appears internally. This is not permitted on a new pipe installation, but can improve the safety of an existing installation. Fire valves are also required for externally located boilers.

    Your OFTEC registered technician will be able to offer advice on the correct selection and positioning of fire valves.

    Annual inspection

    Oil supply pipes must be inspected regularly for general condition and this is often done as part of a routine boiler
    service. Any damage, deterioration or leaks from joints should be repaired at the earliest opportunity. For underground pipes, pressure testing is likely to be required.