Scope

4.1 This guidance is relevant to combustion installations designed to burn oils meeting the specifications for Class C2 (Kerosene) and Class D (Gas oil) given in BS 2869:2006 or equivalent, liquid biofuel conforming to EN 14213:2003 and blends of mineral oil and liquid biofuel.

Appliances fitted in bathrooms and shower rooms

4.2 Open-flued oil-fired appliances should not be installed in rooms such as bathrooms and bedrooms where there is an increased risk of carbon monoxide poisoning. Where locating combustion appliances in such rooms cannot be avoided, a way of meeting the requirements would be to provide room-sealed appliances.

Air supply to appliances

4.3 A way of meeting the requirements would be to adopt the general guidance given in Section 1, starting at Paragraph 1.2, and to provide permanently open air vents as shown in Diagram 40 in rooms or spaces containing appliances. An example calculation illustrating the use of this guidance is given in Appendix D. Where manufacturers’ installation instructions require greater areas of permanently open air vents than those shown in Diagram 40, the manufacturers’ advice should be followed.

Size of flues (other than balanced flues and flues designed to discharge through or adjacent to walls)

4.4 Flues should be sized to suit the intended appliance such that they ensure adequate discharge velocity to prevent flow reversal problems but do not impose excessive flow resistances. A way of meeting the requirements would be to use:

a. connecting fluepipes of the same size as the appliance flue outlet; and

b. flues in chimneys of the same cross-sectional
area as the appliance flue outlet.

When constructing masonry or flueblock chimneys, a way of doing this would be to:

i. make the flue the same size as the appliance flue outlet; or

ii. make the flue larger and of a size that would allow the later insertion of a suitable flexible flue liner matching the appliance to be installed.

4.5 Larger flues may need to be provided where appliance manufacturers’ installation instructions demand this.

Outlets from flues and flue heights

4.6 The outlet from a flue should be so situated externally as to ensure: the correct operation of a natural draught flue; the intake of air if a balanced flue; and dispersal of the products of combustion.

4.7 A way of meeting the requirement could be to follow the guidance in Diagram 41. The separations given in the Table to Diagram 41 are minimum values that may have to be increased where there is a risk that local factors such as wind patterns could disrupt the operation of the flue or where a natural draught flue would not be tall enough to clear the products of combustion of an open-flued appliance. For flues in proximity to roof windows the minimum separation distances identified in Diagram 35 should be applied.

Note: The plume of wet flue products from condensing boilers, positioned in accordance with the safety distances set out in Diagram 41, can sometimes be considered a nuisance for neighbouring properties. Whilst this nuisance is not considered to be within the scope of building regulations, such installations could be considered as a ‘Statutory Nuisance’ as set out in the Environmental Protection Act. As such, installers may wish to adopt the guidance in
Chapter 6 of the Guide to Condensing Boiler Installation Assessment Procedure for Dwellings.

Care may also need to be taken to locate flue outlets away from parts of the building that may be damaged by frequent wetting.

4.8 Flue outlets should be protected with terminal guards if persons could come into contact with them or if they could be damaged. If a flue outlet is in a vulnerable position, such as where the flue discharges at a point within reach of the ground, balcony, veranda or a window, it should be designed to prevent the entry of any matter that could obstruct the flow.

Diagram 40 Free areas of permanently open air vents for oil-fired appliance installations

Diagram 41 Location of outlets from flues serving oil-fired appliances

Table to Diagram 41 Location of outlets from flues serving oil-fired appliances

Flues for oil-fired appliances: flue gas temperature

4.9 Satisfactory provision of chimneys and fluepipes depends upon the flue gas temperature to be expected in normal service and separate guidance is given in this Approved Document according to whether the proposed installation will have a flue gas temperature more than or less than 250°C as measured by a suitable method such as those in OFTEC Standards A100 or A101. Suitable chimney systems may then be selected based on their performance designation having been tested in accordance with the relevant European standard.

4.10 Flue gas temperatures depend upon appliance types and the age of their design. Modern boilers bearing the CE mark, indicating compliance with the Boiler (Efficiency) Regulations (1993), normally have flue gas temperatures not exceeding 250°C. Condensing oil-fired appliances will normally produce flue gas temperatures well below 100°C. Information for individual appliances should be sought from the manufacturer’s installation instructions, from the manufacturers themselves or from OFTEC. Where this is not available, flues should be constructed for an assumed flue gas temperature greater than 250°C.

Provisions for flue gas temperatures in excess of 250°C

4.11 A way of making satisfactory provision for oil appliances in these cases would be to follow the guidance given in Sections 1 and 2 for connecting fluepipes and masonry or flueblock chimneys or to provide a factory-made metal chimney in accordance with Paragraphs 1.42 to 1.46 in Section 1 (but not Paragraph 1.42(b)). However, other products may be acceptable if they have been certified for this purpose.

Provisions for flue gas temperatures not exceeding 250°C

4.12 Satisfactory provision of chimneys and fluepipes for oil appliances in these cases may be achieved by:

a. following the guidance on the selection of components and the manner of their installation as given in Paragraphs 4.13 to 4.20 and the references to Section 1 or (if the intended appliance is new and of known type);

b. i) using factory-made components that achieve a performance at least equal to that corresponding to the designation given in Table 8 (for the intended appliance type) when tested to an appropriate European chimney standard (BS EN); and

ii) installing these components in accordance with the guidance in Paragraphs 4.13 to 4.20 and Section 1, as relevant, and in accordance with the appliance manufacturer’s and component manufacturer’s installation instructions.

Table 8 Minimum performance designations for chimney and fluepipe components for use with new oil-fired appliances with flue gas temperature less than 250ºC

Connecting fluepipe components

4.13 Connecting fluepipes can be constructed using the following components:

a. any of the options listed in Paragraph 1.32; or

b. sheet metal fluepipes as described in BS EN 1856-2:2004; or

c. fibre cement pipes as described in BS EN 1857:2003+A1:2008; or

d. any other component that has been certified as suitable for this purpose.

Masonry chimneys

4.14 Masonry chimneys can be built in accordance with Paragraphs 1.27 and 1.28 in Section 1.

Flueblock chimneys

4.15 Chimneys can be constructed from factory-made flueblock systems primarily designed for solid fuel, as described in Paragraphs 1.29 and 1.30 in Section 1. They can also be constructed from factory-made flueblock systems comprising straight blocks, recess units, lintel blocks, offset blocks, transfer blocks and jointing materials complying with:

a. BS EN 1858:2003 for concrete flueblocks; or
b. BS EN 1806:2006 for clay/ceramic flueblocks, with a performance at least equal to the designation given in Table 8 for the intended appliance type.

4.16 Flueblock chimneys should be installed with sealed joints in accordance with the flueblock manufacturer’s installation instructions. Where bends or offsets are required, these should be formed using matching factory-made components. Flueblocks which are not intended to be bonded into surrounding masonry should be supported and restrained in accordance with the manufacturer’s installation instructions.

Factory-made metal chimneys

4.17 Chimneys for oil-fired appliances can be constructed using the systems described in Paragraphs 1.42 to 1.46 in Section 1.

Location and shielding of flues

4.18 A way of protecting the building fabric from the heat dissipation from flues, where flue gas temperatures are not expected to exceed 250°C, would be to follow the guidance in Table 9.

4.19 Where a fluepipe or chimney penetrates a fire compartment wall or floor, it must not breach the fire separation requirements of Part B. See Approved Document B for more guidance.

4.20 Fluepipes and factory-made chimneys should also be guarded if they could be at risk of damage or if they present a hazard to people that is not immediately apparent such as when they traverse intermediate floors out of sight of the appliance.

Table 9 Protecting buildings from hot flues for flue gas temperatures not more than 250ºC

Relining of flues in chimneys

4.21 Lining or relining flues may be building work and, in any case, such work should be carried out so that the objectives of requirements J2 to J5 are met (see Paragraphs 1.34 and 1.35). For flue liners serving oil appliances, ways of meeting the requirements include the use of:

a. linings suitable for use if the flue gas temperature can be expected to exceed 250°C such as:

liners as described in Paragraph 1.27; ii. liners as described in Paragraph 2.20;
flexible stainless steel liners designated in accordance with BS EN 1858:2008;
other systems which have been certified as suitable for this purpose.

b. linings suitable for use if the flue gas temperature is unlikely to exceed 250°C such as:

any of the linings described in (a) above;
other systems which have been certified as suitable for this purpose;
(if the appliance is new and of known type) flue lining systems that have a performance at least equal to that corresponding to the designation given in Table 8 for the intended appliance type.

4.22 Flexible metal flue liners should be installed in one complete length without joints within the chimney. Other than for sealing at the top and the bottom, the space between the chimney and the liner should be left empty unless this is contrary to the manufacturer’s instructions. Double-skin flexible flue liners should be installed in accordance with the manufacturer’s installation instructions. Liners should be installed in accordance with BS EN 15827-1:2007.

Flues for appliances burning Class D oil

4.23 Flues which may be expected to serve appliances burning Class D oil should be made of materials which are resistant to acids of sulphur, i.e. minimum flue designation ‘D2’ for non-condensing appliances or ‘W2’ for condensing appliances, according to the designation system in BS EN 1443:2003 and related flue standards.

Hearths for oil-fired appliances

4.24 Hearths are needed to prevent the building catching fire and, whilst it is not a health and safety provision, it is customary to top them with a tray for collecting spilled fuel.

4.25 If the operation of an appliance is unlikely to cause the temperature of the floor below it to exceed 100°C, as shown using an appropriate test procedure such as those in OFTEC Standards A 100 and A 101, special measures may be unnecessary beyond the provision of a rigid, imperforate, and non-absorbent sheet of noncombustible material such as a steel tray. This may be provided as an integral part of the appliance.

4.26 If the appliance could cause the temperature of the floor below it to exceed 100°C, a more substantial hearth is required. A way of meeting the requirement would be to provide a hearth of solid non-combustible material at least 125mm thick (which may include the thickness of any non-combustible floor) with plan dimensions not less than those shown in Diagram 24 in Section 2. It should have no combustible material below it unless there is an air-space of at least 50mm between the material and the underside of the hearth, or there is a distance of at least 250mm between the material and the top of the hearth (see Diagram 25 in Section 2).

4.27 To provide a region around the appliance which is free of any combustible material, the appliance should not be placed closer to the edges of the hearth nor closer to any combustible material which is laid over the hearth than the distances shown in Diagram 42. The perimeter of this safe region should be marked to provide a warning to the building occupants and to discourage combustible floor finishes such as carpet from being laid too close to the appliance. A way of achieving this would be to provide a change in level.

Shielding of oil-fired appliances

4.28 Combustible materials adjacent to oil-fired appliances may need protection from the effects of heat. Special measures may be unnecessary if the materials will not be subjected to temperatures in excess of 100°C, but otherwise a way of meeting the requirement would be to protect combustible fabric with:

a. a shield of non-combustible material, such as insulating board with fire-resistant surface; or

b. an air-space of at least 75mm (see Diagram 39 in Section 3).

4.29 Appliances having surface temperatures during normal operation of no more than 100°C would not normally require shielding.

Alternative approach

The requirements may also be met by adopting the relevant recommendations in the publication listed below to achieve an equivalent level of performance to that obtained by following the guidance in this Approved Document: BS 54101:1997 Code of practice for oil firing. Installations up to 45kW output capacity for space heating and hot water supply purposes.

Diagram 42 Location of an oil-fired appliance in relation to its hearth.
Minimum dimensions of the heat-resistant material in the hearth and the clear zone of non-combustible surface

Section 4: Additional provisions for oil burning appliances