Project Description

The Project:

The brief for this project was to design, supply and install new flue systems to serve the proposed 3 No. Hoval Ultra Gas 850 condensing  gas fired boilers. The location of the site was a busy, modern office block within the central London area and we needed to minimise disruption to areas outside of the plant room. After reviewing the options available we decided to reline the existing 70m risers with Furanflex composite linings. This meant that access was only required at the top and bottom of the existing systems for the installation and that all works on this section of the project were completed within just 3 days. The remaining strip out and replacement within the basement area and on the roof were carried out without impacting the inhabitants of the building in any way.


Key factors for the design included:

  • New condensing boilers being installed required a constant fall on the flue system while staying as close as possible to the existing flue routes.
  • Systems to be able to cope with wet, positive pressure conditions created by these condensing gas fired boilers.
  • Installation to be carried out within a short time window and with minimal disruption outside of the plant room and basement areas.

Product Specification:

The following product specification was used throughout the project:

  • Plant Room Flue – Poujoulat Condensor – 316 grade stainless steel single wall.
  • Stack Connection Flues – Poujoulat TI – 316 grade stainless steel liner, 32mm insulation cavity, 304 grade stainless steel case.
  • Lining System – Kompositor Furanflex Black Composite Liner.


The installation of the project took place over a short program in line with the client’s requirements. Chimflue took care of the entire strip out, installation of new primary and stack connections in single wall and twin wall respectively as well as the lining of the existing flues. Due to the restricted and enclosed space at the top of the risers we had to implement a strategy for the extraction of steam (a by-product of the Furanflex installation process) as well as products of combustion from the steam generators situated within the basement at the bottom of the risers. The linings weighing around 500kg each were winched into place using a remote controlled tirfor suspended from an A Frame on specially designed and manufactured spreader beams across the riser shaft. The works were successfully completed within the required time frame and the linings 25 year guarantee handed over to the client.

Download the printable PDF

Get in touch to see how we can help you