Extreme boiler noise

Bowe · 4 Mar 2020

Hi all,

I bought a 1950s bungalow a couple months back and have been slowly renovating it. One of the first things I did, was to redo all the pipework from the boiler to all rads, and replaced all the radiators. The boiler itself is a Bosch boiler which is around 7yrs old. Seemed fine when I bought the place so decided no need to replace. It has one of the "older" style engines in it, which I understand to be better built quality then some of the newer ones.
I replaced the piping (old 8mm) with 15mm and 22mm. 15mm to each rad and 22mm everywhere else. The rads are extremely oversized as I run my boiler with a 55deg c flow temp to keep it in condensing mode (return if circa 45). My issue is that the boiler sounds like it's going to shake itself off the wall now. It's the strangest thing I've ever heard a boiler do. The vibrations are insane. But it doesn't happen all the time. I am unsure if it is the pump, fan or perhaps the expansion tank. Anyone ever had this issue or any ideas how I can test each part so that I can replace the broken thing rather than pot luck it and spend a fortune.

Thanks in advance

ReJect · 4 Mar 2020

Unless you have the gas qualification, you shouldn’t be working inside the boiler.
Have you checked if the pressure relief valve is discharging water when noise is happening?

Bowe · 4 Mar 2020

Many thanks for the reply. I'm not gas qualified, hence not actually doing anything inside the boiler. Just wondering if there is anything that I can do, to make the noise happen/test each part so that actual gas guy can change it. I have had two guys around already and they are both stumped. One suggested to replace the fan just to see if it is that, and the other called Bosch and they didn't have a clue.
Where might the PRV discharge water from/how would I know it is? I am guessing that the PRV isn't on the condensate discharge nor the system drain down valve? I'm not that knowledge about boiler unfortunately.

martin hill · 4 Mar 2020

With you changing pipe work etc you may of flushed some crap into the pump that is now stuck and in balanced the impeller. Pop some x400 in and run the heating for a while. But like others have and will say dont open up the front of the boiler. Thank goodness for my old Baxi 51-rs 3. 0ver 30 years old and not a penny spent on it other than service/check each year.

ReJect · 4 Mar 2020

Bowe said:
Many thanks for the reply. I'm not gas qualified, hence not actually doing anything inside the boiler. Just wondering if there is anything that I can do, to make the noise happen/test each part so that actual gas guy can change it. I have had two guys around already and they are both stumped. One suggested to replace the fan just to see if it is that, and the other called Bosch and they didn't have a clue.
Where might the PRV discharge water from/how would I know it is? I am guessing that the PRV isn't on the condensate discharge nor the system drain down valve? I'm not that knowledge about boiler unfortunately.

The PRV should be connected to a 15mm copper pipe that you should be able to see outside. Sometimes the pipe is turned back towards the wall outside to prevent risk of someone getting splashed with hot water, or it could be piped to near the ground.
Not saying it is the fault, as a decent engineer would most likely have checked that.

Bowe · 5 Mar 2020

martin hill said:
With you changing pipe work etc you may of flushed some crap into the pump that is now stuck and in balanced the impeller. Pop some x400 in and run the heating for a while. But like others have and will say dont open up the front of the boiler. Thank goodness for my old Baxi 51-rs 3. 0ver 30 years old and not a penny spent on it other than service/check each year.

I popped x400 in it a while ago, as I thought it might get ride of it. Did a couple of flushes too. When the first engineer did the boiler service, it was full of crap but he cleaned it all out. Could it be a fault fan? Or I thought with the change in volume of fluid in the system with increased rads and pipes, that the expansion vessel might be struggling.

Bowe · 5 Mar 2020

ReJect said:
The PRV should be connected to a 15mm copper pipe that you should be able to see outside. Sometimes the pipe is turned back towards the wall outside to prevent risk of someone getting splashed with hot water, or it could be piped to near the ground.
Not saying it is the fault, as a decent engineer would most likely have checked that.

Many thanks. I've found that pipe but it doesn't look like any water has come out of it in a long time. But I'll keep an eye on it if / when the noise happens again. If there is water coming out of it, what does that mean? Pressure going to high in the system which could be caused by pump?

ReJect · 5 Mar 2020

Bowe said:
Many thanks. I've found that pipe but it doesn't look like any water has come out of it in a long time. But I'll keep an eye on it if / when the noise happens again. If there is water coming out of it, what does that mean? Pressure going to high in the system which could be caused by pump?

If water is occasionally discharging from PRV pipe it usually indicates the system pressure is too high, so either the system filling loop is passing water through itself, or the expansion vessel isn’t allowing for expansion.
The circulating pump does not increase pressure.