TRV "oscillating"

[RKB]

I have added a small extra rad to my heating system in the downstairs loo. All OK, except when the TRV starts to close, or is it open, it starts banging. To stop it, I just have to turn the TRV setting up or down slighty and it shuts up ... but starts again when the new temp setting is reached.
The system is a combi, and the TRV is on off the shelf from B&Q. Do the high pressure combi's have to have special TRV's??

Need to fix before winter and missus complains about cold toilet seats ..

Thanks in advance

 

[ChrisR]

plenty of stuff here about nosy trv's. First, is it on the correct end of the rad? That often say it doesn't matter, but flow is better.

Second, try turning the lockshield valve (the one the other end) right down.

 

[PEDANTICVINDICTIVEMAN]

B&Q, jeeeeeezzzzzzz.