Knocking noise coming from upstairs radiators

[mcooks71]

Every time our Worcester CDi boiler starts it heating programme there is a persistant knocking noise that comes from 2 of the 4 upstairs radiators. The knocking noise is fairly regular whilst the radiator heats, say 10-15 knocks per min, but reduces after about 20 minutes to about 2- 3 knocks per minute

The 2 that make the noises have thermostatic controls on them, the other 2 (that don't make the noise) do not.

Both the radiators that tick / knock give of ample heat.

The problem has been evident for some time but seems to have got worse since we had a towel warmer type radiator inmstalled in the bathroom earlier this year - problem has only really becom evident as the colder days approach !

I haver attempted to bleed both the radiators as someone advised it may be air in the system, however no air is emitted when I turn the radiator key only water.

Any help or tips on how to remedy this proble would be greatly appreciated- Be aware I am very much a novice in DIY terms so do not be afraid to use very basic dialouge !

Thanks


Mark

 

[Softus]

Might the noises be the result of the metal expanding while it's heating up?

Could be the pipework; could be the rad on its brackets.

 

[Slugbabydotcom]

The 2 that make the noises have thermostatic controls on them, the other 2 (that don't make the noise) do not.

Check the arrows on your TRVs I'll bet fifty pence that they are fitted the wrong way round.
As the rad warms up the heat should follow the direction of the arrow.
Most TRV's now are bidirectional so this is generally becoming less of a problem

 

[Softus]

Excellent Slugbabydotcom - I hadn't considered that one!