A1 Flues
A1 Flues


Should flue firms be Gas Safe registered?

A1 Director John Hamnett's article in the latest edition of HVR asks the question, should flue firms be gas registered?

Here's the full article.

For the first time in my 30+ years in the industry, we were asked by a contractor: “what qualifies you to design a commercial flue system?” We explained that we’re the UK market leader and that we have a clutch of awards – including being HVR’s current Contractor of the Year – and we also pointed to our portfolio of high-profile projects, such as the redevelopment of Battersea Power Station in London. Let me tell you, we have to jump through so many hoops to get projects of that calibre that I should get myself a part-time job working in a circus as a contortionist!

Our credentials and experience are usually more than enough to satisfy even the most rigorous contractors – but in this case, they still wanted more. We got to the point of going through our engineers’ CVs to look at all their qualifications, and then it hit us: we’re Gas Safe registered. It was there in black and white in our accreditations and, as it turns out, that was the proof they were after.

We’ve been Gas Safe registered for a number of years because of the fact that we have employees who have the accreditation. Through our Flue School approach to training and developing, sharing knowledge from best practice around Gas Safe has become part of our DNA in the way we design bespoke flue and chimney systems. It’s also become factored into our bespoke design software that helps our estimators and engineers to design systems.

What’s involved in flue design

Before I continue, it’s important to understand what’s involved in designing a flue, chimney or exhaust system for a commercial building.

  1. Understanding the plant that the system will serve – you need to fully understand both the types and sizes of boilers, generators or CHP units and also the output of the system before you do anything else. We’ve seen it all in our time: from small 300–500 KW plants for schools through to 30–50 MW energy centres for district heating schemes. 
  2. The type of building – hand in hand with the potential rating of the system is developing an understanding of the size, structure and location of the building, as these are all factors affecting how the exhaust fumes flow from the point of combustion and then rise safely and steadily to the termination point. This can vary widely – from a bog-standard office block where the flues rise vertically from the plant room through riser shafts and out via the roof to deliberately unconventional structures, which it seems are solely designed with awards in mind!
  3. Plotting the route of the flue – once we’ve understood the plant and the type of building, we can then start to plot the route. The key here is to work closely with the site engineer from the outset. This is both the most frustrating and ultimately the most satisfying part of the process: coming up with a design that fits with the constraints of the building but does what it’s supposed to – work properly. 

There are so many factors to take into consideration, including the volume velocities, the pressure against draft and the surface temperature of the system

Who is responsible for signing off a flue system?

The reason for covering a few key points of flue design is because it highlights the complex factors that need to be considered. And although we’re in the exhaust end of the business, we have to understand the process that precedes it – and that’s how gas-fired boilers work and what they need to work efficiently and effectively. So that’s why we’re Gas Safe registered.

It all sounds simple and logical to this point, and it begs the question: why doesn’t everyone else in the flue industry follow suit? I’m guessing that it’s because there’s a grey area of responsibility. 

Flues and chimneys are effectively dead systems when work is completed by the installers. Flue companies are handing over systems based on the fact that the systems have been installed to their own guidelines.

However, I’m surprised that more commissioning engineers aren’t kicking up a fuss about this because, under gas law, they are the ones who are responsible for signing off on a plant room – and they carry the blame if things go wrong.

In commissioning engineering circles, flues are regarded as a specialist system, and all they can do is ‘kick the tyres’ of the system by checking joints and seals. They are taking a real leap of faith that the parts of the flue system they can visually inspect are the right specification for the boilers and that it has been installed correctly, before boilers are fired up for the first time. 

If I were in their shoes, I’d be demanding much more paperwork, central to which would be Gas Safe registration to prove that the firm that had designed, manufactured and installed the system could demonstrate that they knew what they were doing.