Plumbing

Gap to cavity behind gas boiler ok?

Anonymous user 09/03/2024 - 3.17 PM

Recently had boiler replaced. Old rectangular vent replaced with smaller round cross section flue. Installer fitted a cut block on inside wall behind boiler but did not mortar/fill in until boiler fitted to wall. Flue is sealed on inside wall above boiler but bottom section of block behind boiler never was. I know this because it is a small room and when I open the door (opens outwards) I hear and see grit/dirt falling into room under boiler from behind it. So air is being drawn in from the cavity. I think flue sealing is necessary but what about this situation? Against regs? (In summary, there is air transfer between room and cavity through the wall behind the boiler.) Edit - thank you for the reply, Llyn Cambrian. Yes, I am trying to get the installer to acknowledge the issue. What you say about no danger would also apply to sealing the flue on the inside wall. But, I do believe the most recent regs say that the flue MUST be sealed on the inside wall in case of damage to flue inside the cavity (however remote the possibility, I believe those are the regs). What about airflow to the cavity behind the boiler? What I want is a professional to confirm that this is against the regs so that I can go back to the installer with some confidence. I simply do not know what is reasonable. If it were a case of completing to my satisfaction, I would also get them to sand down the messy load of filler they have slapped proud against the inside wall around the flue. But a sealed wall behind the boiler (where I cannot access) would do me. So far, over the phone, they have failed to understand the issue. My last resort is the unsatisfactory DIY option of squirting a load of expandable foam behind the top of the boiler; I can just about get a small nozzle pipe in there. Some professionals wonder why people like me prefer to DIY.