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Part J Heat Producing Appliances

Section 1: Provisions which apply to all fuel types


1.1 Guidance

Guidance given in this Section applies to all fuel types and should be read in conjunction with the guidance given in Sections 2, 3 or 4 - Solid fuel, Gas or Oil respectively.

1.2 Air supply to appliances

1.2.1 Each appliance should be:

(a) room sealed, or

(b) contained in a room space or compartment which has a permanent ventilation opening. If this opening is to an adjoining room or space, then the adjoining room or space should have a permanent opening of the same size direct to external air. However, in the case of fixed appliances designed to discharge the products of combustion to the room or space in which they are located, i.e. fixed flueless appliances, the room or space containing the appliance should have permanent ventilation openings directly to the outside air.

1.2.2 Where an appliance that requires cooling air to prevent overheating is located in an enclosed compartment, the compartment should be large enough to enable air to circulate and high and low level vents should be provided.

1.2.3 Ventilation openings should not be provided in internal construction which is required to have fire resistance under the requirements of Part B of the Second Schedule to the Building Regulations. The requirements of Part B may also be relevant to the nature and position of ventilation openings provided in some external walls particularly if the external wall is giving shielding for fuel storage.

1.2.4 Any appliance in a bath or shower room or a private garage should be of the room sealed type. All electric components should be sealed in accordance with the relevant standard where necessary.

1.2.5 Each permanent ventilation opening should be of the recommended size appropriate to the appliance being served and be nonadjustable. Guidance on the size of free area opening recommended for different fuels and appliances is given in Sections 2, 3 and 4, as appropriate.

1.2.6 A permanently open air vent shall be sized so that the free area, or the equivalent free area of a more complex design, is sufficient for the appliance to be installed, taking account where necessary of obstructions such as grilles and anti-vermin mesh. Where two or more components are to be used to provide a non-proprietary ventilation assembly, the assembly should be kept as simple and smooth as possible. The assembly should be taken to have a free area equal to that of the component with the smallest free area in the assembly. The free area of each component should be its manufacturer's figure or where that is not available, its free area measured in accordance with paragraph (see Diagram 1 (b)). The measured free area of a ventilator component is its total unobstructed cross sectional area, measured in the plane where this area is at a minimum and at right angles to the direction of airflow. For an airbrick, grille or louvre, it will be the aggregate free area of the individual apertures (see Diagram 1(c)).

Diagram HJ1 - Ventilation free area - Extract from TGD J
Diagram HJ1 - Ventilation free area - Extract from TGD J Where ventilation is provided via a proprietary ventilator the equivalent area, as declared by the manufacturer when tested to I.S. EN 13141-1:2004, should be equal to not less than 80% of the required permanent free area.

1.2.7 A permanent opening should be positioned where it is unlikely to become blocked or cause discomfort from cold draughts. Cold draughts can be avoided by placing vents close to appliances, (for example by using dedicated ducted floor vents from opposite sides of the building), or by ensuring good mixing of incoming cold air by placing air vents close to ceilings. Openings should not be located within a fireplace recess except on the basis of specialist advice.

1.2.8 Buildings may have gas-tight membranes installed in ground floors to prevent ingress of radon gas or other contaminants. Ventilation ducts or vents installed in floors should not penetrate these membranes in a way that will render them ineffective. Reference should be made to guidance in Technical Guidance Document C in this regard.

1.2.9 Permanent ventilation openings installed to comply with the requirements of this Part of the Building Regulations may serve, in whole or in part, to satisfy the ventilation requirements of Technical Guidance Document F of the Building Regulations. However, controllable background ventilation installed to comply with Technical Guidance Document F requirements should not be taken as contributing to the ventilation requirements specified in this Technical Guidance Document.

1.3 Air extract fans

1.3.1 If an air extract fan is fitted in a building containing a heat producing appliance (other than a room-sealed appliance), the appliance and flue should be able to operate effectively whether or not the fan is running. The presence of some fans may be obvious, such as those on view in kitchens, but others may be less obvious, fans installed in domestic appliances such as tumble dryers and fans fitted to other open flued combustion appliances can also contribute to depressurisation.

1.3.2 Mechanical Ventilation with Heat Recovery (MVHR) systems are not designed to provide combustion air. Where open-flued appliances are installed permanent dedicated combustion air supply is required.

Note: The pressure differences within MVHR systems can easily exceed those within an open-flued appliance. This extends to fan-flued biomass and other solid fuel appliances; although the fan will probably be sufficient to overcome any pressure discrepancies when operational, upon switching off the fan the smouldering fire bed may be reignited and/or spill into the room because of the pressure difference caused by
the MVHR.

1.3.3 Some general installation guidance on air extract fans is given below. However, in order to show that open-flued heat producing appliances operate safely whether or not fans are running, appropriate in-situ tests are required.

The following guidance applies to the installation of different appliances:

(a) For gas appliances: where a kitchen contains an open-flued appliance, the extract rate of the kitchen extract fan should not exceed 20 litres/second (72 m 3 /hour);

(b) For oil appliances: guidance in relation to fan capacities is given in OFTEC Technical Books 2 and 5;

(c) For solid fuel appliances: extract ventilation should not be installed in the same room as an open-flued solid fuel appliance. If mechanical extraction is unavoidable then specialist advice to ensure safe operation of the appliance should be sought;

(d) For commercial and industrial installations, specialist advice may be necessary regarding the interlocking of gas heaters and any mechanical ventilation systems;

(e) When fans are used to extract radon from below a building care should be taken to ensure that air from the building itself is not extracted causing spillage of combustion gases. A fan power in the order of 75 watts is normally adequate. Further guidance is given in BRE Good Building Guide GBG 25.

1.3.4 Tests to check for spillage should be carried out in conditions when appliances are subjected to the greatest possible depressurisation. A prerequisite for this condition is that all external doors, windows and other adjustable ventilators to outside are closed and any fans operating are on their maximum useable setting. The depressurisation at the appliance will depend on the particular combination of fans in operation (fans in the room containing the appliance and fans elsewhere in the building) and the pattern of open internal doors, hatches etc. Several tests (which should include a test with the door leading into the room of installation closed and all fans in that room switched on) may be necessary to establish the specific combination causing the greatest depressurisation at the appliance and demonstrate the safe operation of the appliance with reasonable certainty. The effect of ceiling fans should be checked during the tests.

Consideration should also be given to spillage due to the stack effect of openable roof lights located at high level in a building.

Guidance on appropriate spillage test procedure for gas-fired appliances is contained in BS 5440 – 1: 2008 and BS 5440 – 2: 2009 and for oil-fired appliances in OFTEC technical books 2, 4 & 5. Reference should be made to BRE Information Paper IP 7/94 Spillage of flue gases from solid-fuel combustion appliances and BRE Information Paper IP 21/92, Spillage of flue gases from open-flued combustion appliances.

See also Technical Guidance Document F - Ventilation.

1.4 Chimneys and connecting flue pipes

1.4.1 All heat producing appliances should have a balanced or low level flue or be connected to a flue pipe or chimney which discharges to the external air. However where an appliance is designed to operate without the direct discharge of the products of combustion to the outside air the manufacturer’s installation requirements and the specific ventilation requirements applicable to the product must be complied with (see Section 3).

1.4.2 The development of heating appliances has resulted in new additional requirements for chimneys, e.g. operation with positive pressure, operation with the formation of condensate. A chimney or connecting flue-pipe serving any appliance should be suitable for use with that appliance. Flexible metal flue liners should not be used as a primary liner of a new chimney.

1.4.3 Condensates in chimneys

Chimneys and flue liners should provide satisfactory control of water condensation such as:

(a) for chimneys connected to non condensing appliances the flue liner should be insulated so that flue gases do not condense in normal operation;

(b) for chimneys connected to condensing appliances -

(i) lining components should be used that are impervious to condensate, have suitable resistance to corrosion (I.S. EN 1443 “W” designation) and have appropriate provision for draining, avoiding ledges, crevices, etc. and

(ii) provisions should be made for the disposal of condensate from condensing appliances.

1.4.4 Chimney designation

The characteristics under which chimneys are designated are specified in I.S. EN 1443:2003. These include operating temperature, pressure, condensate resistance, corrosion resistance, sootfire resistance and distance to combustibles, e.g. T600 N2 D 3 G80 (see Annex A).

Guidance on flue pipes and chimneys suitable for use with solid fuel appliances is given in Section 2. These are generally suitable for use with gas or oil-fired appliances which are not condensing. Guidance on alternative provisions, suitable for gas fired appliances or oil-fired appliances (both non-condensing and condensing), is given in Sections 3 and 4 respectively.

1.4.5 Provision should be made to enable a flue to be inspected and cleaned. An opening should only be made into a flue for the purpose of:

(a) inspection or cleaning. The opening for this purpose should have a rigid, noncombustible and gastight cover, or a removable section in condensing type appliances; or

(b) fitting an explosion door, draught stabilizer or draught diverter.

1.4.6 A flue should not open into more than one room or space except for the purpose of inspection or cleaning, but may serve more than one appliance in the same room. However, each solid fuel appliance should have its own flue.

1.4.7 Location of flue outlets

The location of flue terminals specific to the fuel type being used is given in Sections 2, 3 and 4 as appropriate. The outlet from an open-flued, natural draught appliance, for residential heating, (or comparable applications), located on a roof adjacent or adjoining a higher building should terminate above the prohibited zone as shown in Diagram 2 irrespective of the fuel type.

Diagram HJ2 - Open flue, natural draught chimney/flue outlet locations near adjacent or adjoining structures or buildings - Extract from TGD J
Diagram HJ2 - Open flue, natural draught chimney/flue outlet locations near adjacent or adjoining structures or buildings - Extract from TGD J

1.4.8 Repair or reuse of existing flues or chimneys Where it is proposed to bring a flue in an existing chimney back into use or to re-use a flue with a different type or rating of appliance, the flue and chimney should be checked and if necessary altered to ensure that they satisfy the requirements for the proposed use. Defective flues may be relined using materials and components described in Sections 2, 3 or 4 depending on the type of appliance proposed. Chimneys should be swept before relining to remove deposits. A flue may also need to be relined to reduce the flue area to suit the intended appliance as oversize flues can be unsafe. Where a metal liner exists and the appliance is being replaced the condition of the metal liner should be checked and replaced where necessary. Rigid stainless steel flue liners and flexible flue liners, appropriately designated in accordance with I.S. EN 1856-2:2009 to suit the appliance and fuel type, may be used to reline a chimney. They may also be used to connect gas back boilers to chimneys where the appliance is located in a fireplace recess. Existing custom-built masonry chimneys may be lined or relined using rigid or flexible flue liners with the appropriate designation and performance level specific to the type of fuel and appliance to be used (see Sections 2, 3 and 4 for performance levels).

Flexible flue liners may not be appropriate for large non-lined chimneys without specialist advice. Masonry flue liners for use in existing chimneys should be installed in accordance with their manufacturer’s instructions. Appropriate components should be selected to form the flue without cutting and to keep joints to a minimum. Bends and offsets should only be formed with factory made components. Liners should be placed with the sockets or rebates ends uppermost to contain moisture and other condensates in the flue.

The space between the lining and the surrounding masonry may be filled with a weak insulating mix (see sub-section 2.5.3) unless the manufacturer’s instructions specify the contrary.

1.5 Warning of the release of carbon monoxide in dwellings

1.5.1 Carbon monoxide:

To ensure proper combustion and removal of the products of combustion a heat producing appliance should be correctly installed and regularly serviced. The provision of an alarm in accordance with the guidance below should not be regarded as a substitute for this.

1.5.2 Carbon monoxide alarms

Where a new or replacement open-flued or flueless combustion appliance, not designed solely for cooking purposes, is installed in a dwelling, a carbon monoxide (CO) alarm should be provided:

(a) in the room where the appliance is located, and

(b) either inside each bedroom or, within 5 m (16 ft.) of the bedroom door, measured along the path of the corridor. Where a system chimney is being used, with any heat producing appliance and the flue passes within or over a habitable room, (whether encased or not), then a CO alarm should be fitted in the room. Alarm type

A carbon monoxide alarm depends on a sensing element the output of which changes in the presence of carbon monoxide. It has a limited life span and may become obsolete even though the electric circuitry remains functioning which is why an end of life alarm is required.

Carbon monoxide alarms should:

(a) comply with I.S. EN 50291- 1:2010/A1:2012; and

(b) incorporate a visual and audible indicator to alert users when the working life of the alarm is due to pass; and

(c) the manufacturer should have third party certification confirming compliance with the standard.

The carbon monoxide alarm may give an end-of-life indication in accordance with the following criteria:

  1. powered by a non-replaceable (sealed) battery unit where the battery life does not exceed the life of the sensor;

  2. powered by mains electricity(not plug in type) where a timer is included to indicate the end-of-life of the unit;

  3. powered by a replaceable battery where a timer is included to indicate the end-of-life of the unit.

1.5.3 Location

The carbon monoxide alarm in a room containing an open-flued or flueless combustion appliance should be located –

(a) either on the ceiling at least 300 mm from any wall or, if it is located on a wall, as high up as possible (above any doors and windows) but not within 150 mm of the ceiling; and

(b) between 1000 mm and 3000 mm horizontally from the appliance; or

(c) in accordance with the manufacturer’s instruction. Alarms located in bedrooms should be located relatively close to the breathing zone of the occupants. Where a single room serves as living accommodation then the alarm should be positioned as far from the cooking appliances as possible but near to where the person sleeps. Further guidance on the installation of carbon monoxide alarms is available in I.S. EN 50292:2002 and from manufacturers’ instructions.

1.6 Sealing around fireplace openings

1.6.1 Where a decorative treatment, such as a fireplace surround, masonry cladding or dry lining is provided around a fireplace opening, any gaps that could allow flue gases to escape from the fireplace opening into the void behind the decorative treatment, should be sealed to prevent such leakage. The method of sealing and the sealing material used should be capable of maintaining the seal despite any relative movement between the decorative treatment and the fireplace recess. Fireplaces should be securely fixed before sealing is carried out (for further guidance see BS 1251: 2015 Specification for open-fireplace components and Fireplace Surrounds-Stone Federation Data Sheet March 2013).

1.7 Location of appliances

1.7.1 A permanent means of safe access to appliances should be provided for maintenance. For appliances installed in roof spaces, walkways may be necessary for this purpose. Where a heat producing appliance is installed in a domestic or other garage, precautions should be taken to avoid impact damage to the appliance by a vehicle. Such precautions may consist of:

(a) the provision of an adequate barrier around the appliance (see Technical Guidance Document K for guidance on barriers) or

(b) locating the appliance at a level or in a part of the garage where it cannot be struck by a vehicle.

Whatever precautions are taken, adequate space should be provided to allow the appliance to be properly maintained.

*1.8 Notice plates for hearths and flues

1.8.1 Where a hearth, fireplace (including a flue box), flue or chimney is provided (including cases where a flue is provided as part of the refurbishment work), a notice plate containing key information essential to the correct application and use of these facilities should be permanently posted in the building. The information should include the following:

(a) the location of the hearth, fireplace (or flue box) or the location of the beginning of the flue;

(b) the category of the flue and generic types of appliances that can be safely accommodated;

(c) the type and size of the flue (or its liner if it has been relined) and the manufacturer's name (where applicable);

(d) the installation date and the installers name and registration number (where applicable).

1.8.2 Notice plates should be robust, indelibly marked and securely fixed in an unobtrusive but obvious position within the building such as:

a) next to the electricity consumer unit; or

(b) next to the gas consumer unit; or

(c) next to the chimney or hearth described.

1.9 Commissioning

1.9.1 Heat producing appliances serving the total dwelling should be commissioned and tested at completion so that the systems and their controls are left in the intended working order and can operate effectively and efficiently.

1.10 User information

1.10.1 The owner of the building should be provided with sufficient clear and comprehensive information on any continuing maintenance required to facilitate the effective operation of the heating system or systems in order to protect the health and safety of the building occupants.

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