A Salus auto balance UFH valve, could be a simple bolt on to replace a trv. Just open the lock shield fully. Not sure what dT your radiator works at? The Salus above 30 Deg holds a 7 Deg dT and below 30 degs a 4dT. They use a clip on temperature probe on the supply and return piping, but also require a power supply.

The original ones had a couple of hours self commission period, new one fit in place, zero commission period.

Posted by: @johnmo

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A Salus auto balance UFH valve, could be a simple bolt on to replace a trv. Just open the lock shield fully. Not sure what dT your radiator works at? The Salus above 30 Deg holds a 7 Deg dT and below 30 degs a 4dT. They use a clip on temperature probe on the supply and return piping, but also require a power supply.

As I understand it these balance for fixed dT

That's not what's needed unless emitters are perfectly sized (which they inevitably aren't).  What's needed is to balance for room temperature (but slowly, like an lsv being manually tuned,) thus taking out inevitable variations in sizing.  

I agree that the right device would allow lsvs to be fully open.

Posted by: @jamespa

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That's not what's needed unless emitters are perfectly sized (which they inevitably aren't).  What's needed is to balance for room temperature

So a thermostat is what you are describing, that modulates flow instead of shutting it off? So a trv with remote sensor?

Posted by: @johnmo

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Posted by: @jamespa

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That's not what's needed unless emitters are perfectly sized (which they inevitably aren't).  What's needed is to balance for room temperature

So a thermostat is what you are describing, that modulates flow instead of shutting it off? So a trv with remote sensor?

That is kind of what I was thinking.

https://www.wolseley.co.uk/product/drayton-angled-trv4-and-remote-head-15mm-2mtr/?srsltid=AfmBOoo4jcmaNl95M-YB7CJiJLp6XyfxkJfEVR2b-8KGX5CcPcbmJAr5

These have been about for a few decades. Simple. Sure you could get a wireless version. Just look around. Do a basic radiator balance, let them fine tune.

But you really need them, cash rich, time poor maybe, a couple of fine tunes, over a few evenings, no you don't need them. If your radiator sizing is reasonable shouldn't be much to do apart from hydraulic balance. Just follow heat geek instructions on their website.

Posted by: @johnmo

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Posted by: @jamespa

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That's not what's needed unless emitters are perfectly sized (which they inevitably aren't).  What's needed is to balance for room temperature

So a thermostat is what you are describing, that modulates flow instead of shutting it off? So a trv with remote sensor?

Almost but not quite a trv with remote sensor.  A trv with or without a remote sensor operates principally, so far as I know, as an on off device (albeit that there is an element of analogue control).  That's not what we want, we want a device that adjusts the flow on a longer timescale (hours) so that it's just the right flow to achieve the desired room temperature.  WC still applies. 

It's literally the same as adjusting the lsv manually, something you do slowly over hours or days until it's right, then leave forever.

I completely agree that householders could in principle do this manually, but doubt that many can/will hence the need for a fit and forget solution.  Don't forget we need to assume that a)householders have no interest in heating and b) that a high proportion are incapable of (or unwilling to)  following simple instructions.

It's literally the same as adjusting the lsv manually, something you do slowly over hours or days until it's right, then leave forever.

Is that really the case?  Won’t the rate of heat loss in the room change as it cools/warms outside and thus what it is balanced for today at 1c isn’t the same as tomorrow when it’s -3c?  The flow temperature would have increased but is the radiator still properly balanced in the changed scenario?

Posted by: @andrewj

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It's literally the same as adjusting the lsv manually, something you do slowly over hours or days until it's right, then leave forever.

Is that really the case?  Won’t the rate of heat loss in the room change as it cools/warms outside and thus what it is balanced for today at 1c isn’t the same as tomorrow when it’s -3c?  The flow temperature would have increased but is the radiator still properly balanced in the changed scenario?

 

Yes it really is the case to a good (good enough) approximation.  Once emitters are balanced open loop WC with all emitters permanently on works pretty well, and all this is is open loop WC with an automated balancing instead of manual balancing.

Posted by: @jamespa

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Posted by: @andrewj

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It's literally the same as adjusting the lsv manually, something you do slowly over hours or days until it's right, then leave forever.

Is that really the case?  Won’t the rate of heat loss in the room change as it cools/warms outside and thus what it is balanced for today at 1c isn’t the same as tomorrow when it’s -3c?  The flow temperature would have increased but is the radiator still properly balanced in the changed scenario?

 

Yes it really is the case to a good (good enough) approximation.  Once emitters are balanced open loop WC with all emitters permanently on works pretty well, and all this is is open loop WC with an automated balancing instead of manual balancing.

 

That's good to know - and in which case, adding anything fancy to the system to "automate" it sounds like (a) an unnecessary complication; and (b) likely to not work very well and/or just become aggravating (in my somewhat jaded and world-weary opinion)

Posted by: @andrewj

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Posted by: @jamespa

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Posted by: @andrewj

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It's literally the same as adjusting the lsv manually, something you do slowly over hours or days until it's right, then leave forever.

Is that really the case?  Won’t the rate of heat loss in the room change as it cools/warms outside and thus what it is balanced for today at 1c isn’t the same as tomorrow when it’s -3c?  The flow temperature would have increased but is the radiator still properly balanced in the changed scenario?

 

Yes it really is the case to a good (good enough) approximation.  Once emitters are balanced open loop WC with all emitters permanently on works pretty well, and all this is is open loop WC with an automated balancing instead of manual balancing.

 

That's good to know - and in which case, adding anything fancy to the system to "automate" it sounds like (a) an unnecessary complication; and (b) likely to not work very well and/or just become aggravating (in my somewhat jaded and world-weary opinion)

 

 

 

In principle I agree.  However how else can you correctly adjust the lsvs?  Installer won't spend the hours that it takes to do it (they may adjust for DT but won't in most cases adjust for room temperature) and most homeowners not capable/not willing.  The alternative (as I fear the default) is fitting trvs which are a bad option.  

It's a real problem that needs a solution that works for the average householder, not just the ones on this forum!

Posted by: @jamespa

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Almost but not quite a trv with remote sensor.  A trv with or without a remote sensor operates principally, so far as I know, as an on off device (albeit that there is an element of analogue control). 

No they are not on/off valves, they modulate flow. Exactly what you say you want, they do our the box. Modulate radiator flow based on room temperature. So as to keep room a a set temperature. Add weather compensation, they will continue to modulate flow as needed.

Simple description of a trv

https://www.traderadiators.com/blog/how-do-thermostatic-radiator-valves-work

But the disadvantage of trv modulation or any self balancing devise is variation in flow rate at the heat pump. You ideally need as much flow as possible, to give smallest dT to get maximum radiator output, for minimum flow temp, to get best CoP.

Hence the reason everyone is saying minimise their usage.

Auto balance anything, is just a band aid on a fully open system. They really have no place. People should either self install or get a professional install, the professional install should balance they system, if they don't call them back, you have paid good money for an install.