TRV problem? Radiators knocking?

[thesmoothound]

Hi, I had a new boiler fitted 6 months ago and I since then when the boiler fires up the radiators upstairs make a knocking/banging noise on/off for a few minutes.
I think it could be something to do with the TRV's as there were added at the same time. I think the engineer may have put them on the wrong end. The TRV on one of the rads has not been fitted on the flow. Could this be the reason? It doesn't seem to happen downstairs but all of the TRV's are fitted on the left hand side whereas upstairs they are all fitted on the right hand side?
Any advice would be welcomed.

 

[Burnerman]

Although TRV's are supposed to be bidirectional these days, its still better to fit them on the flow....you can determine which is the flow or return by feeling which pipe gets warm first, when firing the boiler up from cold.
John

 

[D_Hailsham]

The noise is the valve jumping due either to incorrect installation or the system not balanced properly.

Most TRVs can now be fitted on either side. Have a look on the metal body for an arrow or two arrows at right angles. If only one arrow, it must be fitted with the arrow pointing in direction of flow. Feel the pipes to see which is the hotter. The arrow should point towards the rad on this pipe and away from the rad on the other.

If the TRV has two arrows at right angles, it can go on either end.

The fact that they are at different ends downstairs from upstairs is not important.

If the TRVs are all correctly installed, the problem will be due to the system not being properly balanced. Get the installer back to check and rebalance.

 

[TicklyT]

you can change the orientation of some types of TRV by mounting it with the valve head either horizontal or vertical. That changes the flow direction through the valve body without swapping it to the opposite end of the rad.

Horizontal TRVs are like Marmite. Some just hate the idea of it, others wouldn't have it any other way.