Another central heating question

ploppy

The Mother in Law has been complaining (for a change :P) about her central Heating making a repetitive tapping noise. Thought it might have been the pipes/radiators expanding/contracting but it still goes on after a few hours.
Added some additive style liquid claiming it cured knocks and kettling and boiler noise but it has run through the system for around 10 days and hasn't nade any difference so far.
Any ideas or advice greatly appreciated. ;D

crapley

If the boiler is a combi check the water pressure.
If there are thermostatic radiator valves on the system try changing the settings, as valvles close when reaching temperature they can chatter.
There may be air in the system, check radiators for air by using bleed nipples.
Unfortunately if the system is old it is likely to contain a lot of silt and will need a drain down and flush through.
Hope this of some help

ploppy

cheers for the replies. It is a combi boiler which is just under 4 years old (same with radiators), it has been drained down then re-filled, with additive added as stated. No thermostatic valves, just ordinary, system has been bled a few times to no avail.
Knocking seems to be coming from the radiators and pipes rather than the boiler itself.

Gaz_Hammer

There's a high probability that its expansion noise then.
I have seen/heard it before where the rad expands against the brackets (on some make of rads they provide a plastic clips which fit in the slot where the rad hangs to stop this type of problem - however they normally get thrown away or deteriorate with age)

Gaz

ploppy

any way to cure gaz_hammer

Gaz_Hammer

Hi ploppy,
To establish if its the rads - while the noise is happening go to each radiator one at a time and see if there is any discernable movement on the bracket (gently move the rad back and forward) and see if it alters or stops the noise in any way.
Points to note for safety:-
1. Obviously if the rad is hot use a cloth or towel to stop being burnt.
2. Don't move the rad too much as it should only be a small movement anyway (Don't want it coming off the wall!)

If its not that then the only alternative is to start tracing the route of the pipework from the boiler to see if its touching floorboards or joists etc. This will probably entail lifting some boards.
If as you say the system is only approx. 4 years old then hopefully the boards will have been screwed down and not nailed!

Let me know how you get on!
Gaz