Safety first for flues

The Gas Safety (Installation and Use) Regulations (GSIUR) 1998 deal with the installation, maintenance and use of gas appliances, fittings and flues in domestic premises and certain commercial premises. However, the HSE and CORGI expressed concerns over non-compliance, following incidents in 2008, and took prompt action to inform developers and contractors, landlords and property owners of the potential dangers from certain types of flues connected to gas-fired central heating installations in some properties.

The HSE became aware that some of these flues may not have been properly installed, or may have fallen into disrepair without anyone noticing. They often referred relevant parties back to the requirements of the GSIUR, but, in some cases the GSIUR instruction has been misinterpreted, particularly where boilers have been installed into apartments and flats.

The introduction of extended twin and concentric flues has encouraged the practice of passing flues through ceiling voids and roof spaces. Most flues are 1-2 metres in length and require several joints, fastened together with a push/fit method. If the regulations are not followed correctly, an incorrect installation may put occupants at risk. CO may enter the ceiling void/enclosure through any breaks in the flue – for example, where joints are not sealed properly or where the flue material has degraded over time. It could then enter the living spaces above and below the flue and become a potential killer.

Make it safe

It is vital that the flue can be visibly inspected through its whole length, both at commissioning and annual service. Access points are required at strategic locations, such as where a change of direction takes place and where the flue enters the void. Ensuring the joints are secure is of paramount importance – every joint that is not secure runs the risk of subsequent separation. Reducing the number of joints reduces the risk and minimises the amount of inspection points required.

It is important that the flue is supported throughout its length, to prevent sagging which places strain on the joints. Adequate fall on the pipe is required to prevent build-up of condensation, which will also increase joint pressure. The joints themselves should be constructed in such a way that they cannot leak or pull apart, whatever the circumstances. Manufacturers provide detailed instructions that should be followed to the letter.

A new solution

Keston has developed an extended-length flueing solution, incorporating fewer joints and thereby reducing associated risks, meeting all GSIUR requirements as well as providing versatility for building designers. The majority of Keston boilers can be flued with widely-available 50mm PVC-C waste pipe, to BS5255 and/or BSEN1566-1, and fittings to BSEN1329, so there is no need to buy bends, terminals and pluming kits. The flue terminals come as standard with every Keston boiler.

Flueing with PVC-C is achievable because of the low flue-gas temperatures in Keston boilers (below 60°C) which also means they are extremely energy efficient. The low-cost plastic pipe can save thousands compared with traditional flue systems as it costs less than £4 per metre and is readily available from all builders’ merchants.

Where joints are used, these are solvent-welded, rather than push fit, reducing the risk of the joint separating and any leakage. PVC-C is also strong and flexible, strong enough to take some heavy impacts without cracking and it doesn’t deteriorate with age or ultraviolet radiation. Cosmetically, PVC-C is available in a choice of colours, and flue terminals can be made to match almost any wall finish.

Swept 90 and 45 degree bends, allow the flue installation to go almost anywhere, horizontally or vertically, and as the components are designed to withstand the weight of water, the pipe brackets are standard and robust, so supporting the system is simple. As the system is only 50mm in diameter, it falls comfortably within a void and inspection of its length can be achieved easily using a minimum amount of access points. The system also uses separate air and flue pipes, which can be of different lengths and orientation, meaning the flexibility of boiler positioning is greatly increased.

When choosing a boiler and flueing system, safety must be the primary consideration, but by following the GSIUR guidelines does not have to mean a compromise in boiler location. Keston’s solution provides the best of both worlds – safety and versatility – made possible by high energy-efficiency resulting in low flue gas temperature.

The solution in action

Keston’s unique flue solution is ideal for buildings with difficult flue requirements and in particular in refurbishments projects where there isn’t a need for the expensive realigning of the flue. In addition, listed buildings can benefit from the Keston flue system as the stringent requirements can make running a flue difficult.

At 1 Harley Street, the existing boilers were beyond repair and the use of conventionally flued boilers was out of the question, due to certain damage to the brick stack, so Keston’s versatile flue requirement and bespoke rigs provided the perfect solution.

A four-boiler C55 rig was installed, incorporating controls, including weather compensation, with domestic hot water supplied by a Keston spa cylinder. The system is flued using Keston’s 70mm composite flue pipe, running 15 metres from the basement at the rear of the building and then vertically up the outside wall.

At LA Fitness in Aldgate, the existing hot water system, consisting of two balanced flue water heaters, had low-level flue termination, which meant that combustion by-products spilled into the occupied courtyard,

Electrical hot water generation was considered, avoiding the need for flues of any type, however a three-boiler C55 Keston rig, coupled with two Keston spa 300’s, to provide 3,000 litres of domestic hot water an hour, was found to be the best solution.

Utilising Keston’s unique flue solution, the flues now run from the plant room through a ceiling void and terminate on the outside wall, three metres from road level.

How to avoid CO poisoning

In 2007/8, there were 150 incidents of carbon monoxide (CO) poisoning: a 30% increase on the previous year and a 60% increase on the 2003/4 figures, according to provisional figures from the Health and Safety Executive (HSE). In 2007/8 there were 14 deaths related to CO poisoning and 234 injuries, compared with 10 and 184 in 2006/7.

According to the HSE website, all gas appliances need an adequate supply of air to help the complete combustion of gas, and efficient operation of their flue to remove any combustion products that are produced, including CO. Without these safety precautions dangerous levels of CO can build up with the possibility of fatal consequences. To avoid CO poisoning – never block ventilation; ensure that flues are kept clear at all times; and have your appliance regularly maintained and annually serviced by a Gas Safe Registered engineer.

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