@alfapat The radiator / emitter that takes the longest to heat up will be the one LSV that remains fully open and all others will then end up somewhere between almost fully open and almost closed (though in practice, this means just a half turn or so from closed due to the nature of the valve’s design in many cases) The aim is to have as low a resistance to flow as can be achieved - hence one LSV being fully open - all others are compared to this in the end. By the way, it is quite possible that the radiator / emitter right at the end of the pipe run will be fed by the water that has released some heat by the time it gets to there and might well be the LSV that remains fully open BUT … this is not a given, an over or undersized  radiator / emitter elsewhere might require more / less throttling to achieve a balance! My wife occasionally challenges me when I am walking around the house with a radiator key! Not so much  a science but an art! Regards, Toodles

@jamespa All Rads sized.

Posted by: @alfapat

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@jamespa All Rads sized.

... in theory!

If they are all (close to ) perfectly sized then adjusting setting them up for consistent deltaT across the radiator is another way to balance.  Some plumbers do this by 'feel' I am told. 

Its still the same laborious and iterative task of adjusting the LSVs though.  We definitely need a variant of a TRV that does this automatically.  It should never (or almost never) shut down completely and should work out how much to throttle by over a period of a few days.  The hardware exists, it needs the right firmware, not sure whether all the TRVs in the house would have to communicate to make it work or whether they could use some sort of random delay protocol (a bit like ethernet).  Essentially Adia are creating a system to do this with a central controller (which communicates with the heat pump - ideal but potentially limiting as they dont support all heat pumps); doubtless they have some future development ideas in mind.

@jamespa If only! 
Hindsight is great , but I was presented with the design 8 yrs ago , so I can only hope that they do the job , most of the time when the temperatures are there when required , they seem to do the job. 
It’s the cost of doing it !

Still at it here , correct me if I am wrong , I am still adjusting lockshields and happen to put a simple temp probe on ingoing /outgoing pipes at the Rads and the temperature at the TRV is higher than at the lockshield is this right. 😕 Surely the flow is lockshield to TRV which incedently is fully open

@alfapat I think modern TRVs can be fitted on either side. The lock shield will restrict flow whichever side it is sited

@bontwoody Thanks , In thought it was a dumb question but hey ho you learn something new every day. Slowly getting round to turning lockshields down.

@alfapat There is no such thing as a dumb question, just a dumb answer 🙂

@alfapat One would expect the flow to be into the emitter from the TRV but, my installers informed me that the modern valve bodies are so made that direction of flow is no longer important. In terms of the LSV, it is restricting the flow, regardless of whether it is in the flow or return run. Regards, Toodles.

@bontwoody We all learn summat every day - it is just that some of us (me in particular) forget to remember it!😉 Regrets, Toodles.

Posted by: @toodles

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@bontwoody We all learn summat every day - it is just that some of us (me in particular) forget to remember it!😉 Regrets, Toodles.

🤣

The bodies of TRVs usually have an arrow on them.  If it can operate bidirectionally it will be a bidirectional arrow!