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Fan-Flued Gas Boiler Safety

INTRODUCTION


The introduction of fan-flued gas appliances in the mid-1990s allowed gas central heating boilers to be installed away from external walls. As a result, specifiers are able to design both new-build and refurbishment of properties with boilers installed on internal walls, making better use of the available space. In these circumstances, flues are often routed through voids in the ceiling space and through stud walls.


Such installations are a common feature of new-build flats and apartments completed since 2000 and may also be encountered in offices and other commercial buildings.

 

SAFETY PRECAUTIONS


Irrespective of the type of boiler, gas engineers are legally required to check that the flue has been installed in a safe manner, both at the time of the original installation and during subsequent servicing and maintenance, and need to be able to check that:


  • the flue is continuous throughout its length;

  • all joints are correctly assembled and are appropriately sealed; and

  • the flue is adequately supported throughout its length.


In order to facilitate these checks in respect of flues routed through voids and stud walls, it is necessary that appropriate inspection hatches are provided. Information provided by the HSE indicates that this has not always been the case and incidents of carbon monoxide poisoning have been recorded where a flue fault has existed in combination with a boiler which is not operating correctly. Guidance contained in Building Regulations (Approved Document J) for the provision of such inspection hatches is as follows:


  • all voids containing concealed flues should have at least one inspection hatch measuring at least 300mm square;

  • no flue joint within the void should be more than 1.5m distant from the edge of the nearest inspection hatch;

  • where possible inspection hatches should be located at changes of direction; where this is not possible, bends should be viewable from both directions.


Under the jurisdiction of the Gas Safety (Installation and Use) Regulations 1998, with effect from 1 January 2013 all installations described above are required to be fitted with appropriate inspection hatches. Any gas engineer working on affected systems after this date is required to formally advise the client that the system is “at risk” and is to seek permission to turn off the appliance until inspection hatches have been fitted. It should be noted that whilst the installation of carbon monoxide alarms is highly beneficial, they do not remove the need for the installation of inspection hatches.


All gas fired boilers irrespective of the type should be serviced and maintained in accordance with the manufacturer’s instructions, normally at annual intervals, by a Gas Safe registered engineer. (Whilst not within the scope of this Technical Bulletin, oil fired boilers also call for annual servicing and maintenance by an OFTEC [Oil Firing Technical Association] registered technician.)

                                                          

PASSIVE FIRE PROTECTION


It is important to recognise that the installation of inspection hatches in the circumstances described may compromise the fire safety design of the building. In these situations, it is essential that suitably fire rated hatches are provided. A range of fire rated hatches are available from a number of manufacturers/suppliers with resistance ratings (integrity) of up 120 minutes.

 

SURVEY EXPECTATIONS


In all cases where fan-flued gas fired boilers are identified, for instance when installed against an internal wall with the flue routed through a ceiling void, enquiries and observations should be made as to the presence of inspection hatches. In the event that this cannot be confirmed, a risk improvement (Requirement) shall be made based on the following wording:


Fan-flued Gas Boilers

All voids containing concealed flues should have at least one inspection hatch measuring at least 300mm square. No flue joint within the void should be more than 1.5m distant from the edge of the nearest inspection hatch. Where possible inspection hatches should be located at changes of direction; where this is not possible, bends should be viewable from both directions.

Where installing inspection hatches in fire resisting walls and ceilings, care should be taken to ensure that the correct hatches are installed which mirror the fire resistance rating of the wall or ceiling in which they are to be positioned, ensuring that the fire safety design of the building is not compromised.


It is recognised that surveys of apartment blocks and other residential property can often present problems with access. Nevertheless, it is considered important that Consultants are aware of this issue, and that they respond as required when surveying premises where fan-flued gas fired boilers are installed.


Inspection hatches typical of many which are marketed for the inspection of flues

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