Increasingly noisy heating system... Advice needed please...

[tgs166507]

Good morning. I have a baxi duotec boiler installed at home, and whilst the boiler seems fine, the overall system seems to be getting increasingly noisy.
Whilst there is the usual expansion noises on startup there is an awful lot of noise seemingly every time the boiler fires.
The noises are a ticking or tapping from most of the radiators, and whilst fairly low level, it is sufficient to stop us going to sleep or to wake us up in the morning.
I've bled the radiators and can't find any significant air in the system. Having said that, I have not bled the expansion vessel on the boiler itself.
The noises happen regularly, in bursts, whilst the heating is on, so it's not the initial system expansion. It seems to happen every time the boiler fires, and the ticking varies in pace over about 15-20 seconds...
The radiators have conventional valves on them, and I plan to change them to trvs this winter but I need to sort this noise out first.
From a heating perspective, the system seems to work well, in that the radiators get pretty hot!
I've not noticed any issues with the hot water. in fact, the main time we notice the issues are when the family are in bed, so it's definitely not related to the hot water side...
I would be very grateful of any advice or pointers as to what I should do next. Thank you very much in advance for your advice.

 

[ianmcd]

Do not touch the expansion vessel, it has absolutely nothing to do with your problem and you will only make things worse if you mess about with it.

 

[John D v2.0]

Probably the pipes expanding and rubbing against the joists and floor boards. You can use talc as a quick fix but the proper fix is to make sure they're not pressing together by opening up the holes if possible, and clipping them properly. You can put pads around the pipes to space them from the timbers. Long straight pipe runs can suffer worse.
Also reducing your heating water temperature can help, at this time of year it's a waste of money to have it on max anyway.

 

[Nige F]

Can you see the brackets behind the rads - they should have small plastic inserts in the U shaped cutout the rad sits in . You can get spare ones on eBay. Try on one rad and see