Water hammer with smart thermostatic valve

[JImCPN]

I have gradually fitted smart TRV's to all of the radiators in our house, and in general we are very pleased with them. However, it has become apparent that quite often, when the timing makes the TRV switch off, this sets off water hammer in that radiator. This is easily fixed by running a hot water tap anywhere, but it is a nuisance. It would appear that the pump doesn't like the sudden switch off - understandable but I am surprised that I can find no mention of this problem anywhere. It surely is quite (very?) common. And is there anything that can be done about it? Now we think we understand the issue we have arranged a sort of partial workround for the end of the day - ie the CH to close down in the evening at 9.45pm with the majority of the smart TRV's closing down at 10pm. But the whole idea of the system is to keep the CH early morning to night with the TRV's making the setup of each individual room much more flexible. It works well .... apart from this problem

 

[Aquarius]

Every radiator shouldn’t have a trv fitted, at least one shouldn’t be fitted, or have a bypass fitted.

 

[JImCPN]

Actually there is one radiator without a valve (in the bathroom). Thanks for this, but I don't think it is the problem - the noise has a tendency to occur in any of the radiators when the valve closes quickly ie when the timing instructs it to do so. Not inevitable, but pretty dramatic when it does. The instructions that came along with the smart TRVs makes no mention of this as a problem - and nor can I find any mention of the problem on the Net.

 

[Gasmk1]

turning your hot water on means that the fault is on the try not being strong enough to withstand the pump so it is chattering, it won't be s sudden switch off it will be gradually as the motor turns it off so it will chatter until fully of if it doesn't stop you need a full new valve. also was the original body Bi-directional if not it will be on the wrong side, so either swap of fit new BI-directional valve