Technical

Technical Sales Director Richard Parkhouse takes a look at relevant standards applicable to design in commercial buildings.
Within our industry we all like to think we are capable of designing a system that the client wants and that will work and perform as expected. I recall an architect saying to an engineer “I expect it to look good and work properly”, to which the engineer replied “As an engineer, I expect it to work and hopefully look good as well”. Many British standards are quoted in the market place and it can be confusing.

One particular standard we all use is BS6644, last published in 1991. It tried to encompass many practices of the time, but little or no changes have been made since that date.

In 1998, the Institute of Gas Engineers was approached to look at the standards to give a full update. All areas were given attention, for example ventilation rates, terminal heights in conjunction with the Clean Air Act Memorandum and fan dilution criteria to name but a few. Their review will shortly be published under the listing of UP/10. It will encompass all updates for BS6644 as well as sections previously covered by IM/11.

It is hoped that we can all feel secure in the knowledge that as time marches on and advances and improvements made the old ways are kept as up to date as possible in this modern, fast-changing age of ours today.

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A GOOD GUESS DOES NOT MAKE FOR GOOD FLUE DESIGN.
Richard Parkhouse of A1 Bridge Flue Systems advises that effective communication and a willingness to work together will raise industry standards...

A flue system should be simple. Its sole function is to evacuate the products of combustion to the atmosphere.

As flue manufacturers, our objective is to get it right first time, every time - but on occasion, we are brought in at the tail-end of a project because the flue system is all but forgotten until the last minute. This means the pressure is on to complete the job on time to a predetermined price.

In a perfect world, the consultant would determine the requirements for the flue system at the same time as the main design, briefing the contractor accordingly. The flue manufacturer can then produce the right flue system in the right materials to an agreed budget.

We live in a competitive world, but there has to be a minimum price for every job. That price tends to be determined by the contractor and not the consultant, even though he is paid to design the job and put his reputation on the line in doing so.

When called in to replace and improve flue systems, we have encountered situations where instead of using materials of the right specification that stand the test of time, very basic materials have been used - obviously not a sensible solution. The very fact we have been called in to replace the work demonstrates the dangers and additional costs inherent in cutting corners. Reputable flue manufacturers would never supply inappropriate materials for a project - and those contractors placing orders should beware of the dangers of using ‘cowboys’ who are not qualified to produce safe and suitable products.

The introduction of the soon-to-be-realised utilisation procedure UP/10 which supersedes the existing BS6644 should go a long way towards rectifying the standard of material specifications.

So I hope the following ‘points to ponder’ will shed some light on the necessary planning required for an effective flue system to be installed.

Always use a specialist flue manufacturer - it is what we do. We understand flues. We know the law. We meet or exceed the current standards and are actively working to set even higher standards within the industry.

When specifying a boiler, water heater or any heating appliance, ensure the draught requirements are included in the specification or performance schedule. The outlet draught requirements, be they negative or positive over its firing range, is as important as pump duty or fan volume/pressure. Without that information, assumptions have to be made in the absence of accurate technical literature - and we don’t believe that working on assumptions is acceptable practice.

When detailing the flue route on all types of pressure jet or blown gas boilers always show booted or swept tees on the boiler outlet. This will overcome the potential of reverberations on a boiler.

When lining an existing chimney that has been used on a boiler producing 8/9% CO2, i.e. pressure jet, oil firing or blown gas, pay particular attention to the internal size of the flue when considering atmospheric boilers as they produce a greater volume of flue gas by virtue of their lower CO2 content and generally require a larger diameter.

The Council for Registered Gas Installers sums up good flue design as follows:

“The correct efficient discharge of an appliance’s combustion products is an essential safety feature and a mandatory requirement of the Gas Safety (Installation and Use) Regulations.

“The appliance and flue manufacturers instructions must always be consulted and due consideration given to Building Regulations and other statutory documents.

“Good flue design is not by chance - but the bringing together of all the relevant information and using it to produce the correct design”.

By communicating effectively at all stages of the process we can then manufacture and install the best system in the most appropriate material and benefit from effective and efficient results.

By approaching the flue system as a ‘bolt-on’ at the end, with no regard to price and sketchy information, the reputation of the industry as a whole will be damaged and safety undermined.

If the UK does not have rigid and proven codes of practice and standards we could well end up having European legislation forced upon us to the benefit of non-UK contractors and manufacturers. It is up to us all to create a level playing field - and strive for good practice. With better planning and more effective communication, this is certainly within our reach.