JamesPa

... and your alternative plan is... Its all very well to criticise others, in fact its the easiest thing in the world. More difficult is to have a realistic constructive and thought through alternative which has some chance of passing the test of political reality. That's what politicians have to do. I don't envy their task to be honest particularly with the amount of mis information (aka lies) out there. Id far rather have a politician that is trying to do something, than one that is actively promoting things which are objectively at variance with the scientific facts. At least the former probably has the right motives, whereas the latter clearly does not. SOFAIK the UK is committed to net zero by 2050, which is a long way off still and we will probably miss, if the history to date is anything to go by. in your 'orderly sensibly paced transition' which 'is fine and achievable' what should the 2050 date be replaced by?

As you say house builders will always protect their profits. These exist in large part because they ration the housing supply. I am frankly not sure the standard makes that much difference (although they will of course always argue against it), but the rationing certainly does. Somehow Government needs to get to grips with this rationing. It may well be that the only way to overcome it is to create a publicly owned house builder which is not motivated solely by profit. They of course will be hampered by the fact that the private developers have already bought up (or have options on) most of the land rights, so land/planning reform of some kind is likely also necessary. This is clearly a long term project, 10 years at least to make an impact. If anyone can suggest an alternative way then it would be interesting to discuss, but while housebuilders are strongly motivated to ration the supply of houses its difficult to see how the supply will increase materially.

Which is precisely what we have been doing for 50 years, which is why it has now become a crisis. Unfortunately the physics doesnt care one iota about what you, I, the reckless climate change deniers or the selfish 'do nothing' merchants think, it will do what it will do. Furthermore if anyone is stupid enough to believe that they are more powerful than nature, so preparing for it will alone be enough, then they should study the videos of California to see just how pathetic the efforts of human beings look for example when dropping fire retardant onto natures flames. Nature is far bigger than we are and we had better get over than. Actually i dont think anyone is stupid enough to believe that, including the world leaders who posture as denialists. They are just looking after their own interests at the expense of our children (nb not theirs, theirs will be housed in bunkers). Sadly that is probably not now possible. If we had limited population growth and if we had taken action on climate change 50 years ago, then maybe. We did neither and have now created a crisis. Yes it does, but that doesn't have to mean fossil fuels. There is more than enough energy falling on the earth from the sun, and sloshing around in our oceans due to the moon, to fuel our economy and harvesting at least the first of these it is pretty cheap. The pain is largely in the transition, not the end point.

Well thats interesting thanks. On my system the compressor bar diagram seems to show 80% during defrost recovery but if I go to information - live monitor it shows 99.8%, and it does definitely seem to be affected by NR mode. Regarding the NR mode 'limits' I just checked mine (previously I had only read the manual) and it does, as you say, allow for -30% even though, as you also say, the manual says 40-60%. Thanks for the tip off!

Yes and it makes some difference to noise but without materially compromising performance. However it too has a limited adjustment range and the two ranges don't overlap. Taking NR and current limit together I can limit max compressor on my 7kW unit to between 40%-60% or between 90%-100%, but not to a value in the range 61%-89%. Somewhere around 80% would very likely do the job in my case, but is not available. Very annoying and somewhat inexplicable.

Nothing as far as I am concerned, but neighbour says he is very noise sensitive and objected to my planning application. So a way to manage it would be rather helpful.

That's quite an interesting feature, at least to me! My Vaillant heat pump is whisper quiet, except when recovering from defrost, which is the only time the compressor modulation reaches anything like 100%. In stable operation, even when its -5, it rarely gets above 60% and never above about 75% and at these levels the unit remains whisper quiet. Invoking a backup heater and clamping the max compressor modulation during recovery from defrost would meant that it would be whisper quiet all the time. SOFAIK however, Vaillant dont support this. Do you happen to know of any manufacturer that does, it might help me put some pressure on Vaillant!

Sorry but thats obvious nonsense. Im not disputing what your system says, but it cannot be the truth unless you were also very cold today. I dont think these figures are telling you anything. Thats the thing to do as a starting point. Also perhaps monitor your electricity meter as well as anything the heat pump tells you (since the latter is suspect). Adjusting the WC curve might require a bit more iteration that this though. There are various 'procedures' you can use ( @JohnMo has a good one), ask again if you are having trouble.

For my money this change has to happen and is logical from a policy perspective (the current position is wholly incoherent) I shudder, though, to think about the headlines is certain parts of the press when/if it does! Not to mention what Elon Musk will say.

Interesting thought. It also occurs to me that, to be useful, a 'smart lockshield' for heat pumps doesn't have to learn. It could simply switch between states (numbered say 1-10) based on time of day, and the user could just pick the states, much like they do with mechanical TRVs which have numbers not temperatures on. Of course it would be better if they did learn, specifically for automating balancing (for which I think they would also have to be networked), but the simplest useful version need neither learn nor be networked

Same question as for Loxone. Does it control temperature by alternately shutting down and opening up like mechanical TRVs, or does it act like an automated lockshield controlling temperature by throttling the water supply but never closing it down, learning the 'correct' position in slow time (days probably) on the assumption that WC is in operation. For heat pumps we need the equivalent of an automated lockshield that never closes down, not a smart equivalent of mechanical TRVS that control temp essentially by on/off modulation.

I can do this with a standard 'smart TRV'. The problem is that it will, so far as I can tell, periodically shut down altogether (ie it will achieve the objective by time modulating). That's not what is required for an efficient heat pump implementation, it needs to partly shut down so that, over time, it achieves the lower temperature, but never completely shut down. Do Loxone TRVs do this (learning, over a period of several days, the setting needed to achieve the setback temperature) or do they alternately shut down and open up? Basically we need a trv that operates like an automatic LSV, alternating between states corresponding to different room temperatures (on the assumption that WC is in use) but never closing off and preferably learning in very slow time.

Even more so for a heat pump which, in weather such as we are currently having, must stop heating and run a defrost cycle periodically, to remove accumulated frost from the air to refrigerant heat exchanger. This is done (in most but possibly not all heat pumps) by robbing the energy from the central heating water to provide the required heat. That's one reason, possibly the principal one, for a minimum system volume and why a volumiser is sometimes required for the amount available to be sufficient. The cloud of vapour when a defrost cycle runs is quite impressive!

By saving I meant cost (energy in) not demand and with this interpretation I think it is true. If, with adjacent rooms unheated, you keep the temperature of the heated rooms at the design temperature then your paper (and HG) shows that bad setback occurs. If you don't keep the temperature of the heated rooms at the design temperature (you allow it to 'sag' in your words) then there is a saving (in cost). The material difference between the two scenarios is the temperature of the heated rooms not the temperature of the unheated rooms. This stuff is difficult to grapple with, I acknowledge, which is why discussion/peer review is vital. A few posts ago I tried to define the 'control' conditions (which I admit is difficult, but is absolutely vital).

@DamonHDHere is another real-world scenario where a more intelligent TRV designed for heat pumps would be useful: In common with many, I like my bedroom to be a bit cooler at night than the parts of the house that I am in most of the day. The standard design temperatures used to size radiators take this into account. However I would ideally like it warmer just as I get up, so I don't have to get up to a cool room. Currently the only ways to achieve this are: a. use a smart TRV with timer, but that involves on/off control of the radiator which is bad for the heat pump efficiency and defrost volume b. set back the whole house at night and raise the temperature just before getting up - but I dont want to do this because I have a ToU tarrif that is cheapest at night, in fact I actually want to set the whole house forward. A TRV properly designed for heat pumps could enable me to do this. To the best of my knowledge no such device is available. Another risk, incidentally, with TRVs is that they can deprive the system of volume for defrost. As a minimum this means that defrost takes longer, in the worst case it could (possibly) lead to a 'freeze down' where there is insufficient volume of hot water to defrost the unit without taking the FT below the dew point, and so it never recovers or takes an extremely long time because it is reliant n heat from the fabric. In my real world scenario above the radiator in question is a not insignificant part of the total system volume and so having a TRV which takes it out of circulation for part of the time is a very bad idea on days like today, when defrosts are occurring about once per hour! Again a TRV designed for heat pumps wouldn't do this.

As @marshian says above a correctly set up system demands that the WC curve is adjusted so that the house just heats to the correct temperature with no other controls, the most efficient way to run a heat pump. It might be notionally computed at design time, but in practice heat loss calculations are a bit of GIGO whatiffery and in reality, for a system to be set up correctly, the WC curve must be adjusted onsite. IMHO the starting point for any calculation such as the one you are attempting to do must be a correctly set up system (or, it it isnt, the assumptions about how it is incorrectly set up must be part of the conclusion). The more sophisticated heat pump controllers will automatically tweak the WC curve a bit from the initial set up, in order to get it 'correctly' set up. So in your scenario it will respond to the fact that some rooms are not heated by slightly jacking up the WC curve instead of having to do it manually. But I believe you miss the whole point - those under heated rooms are pulling heat from the warmer ones. That in effect makes a bigger demand on the heated rooms, so you need to run the system flow temperature higher to compensate. That reduces CoP. Recovery of under heated rooms will be very long if you ever need heat also. The only way that can be effective id running the flow temperature higher than required and a further hit on CoP. Well put @JohnMo You dont need simulations to work this out, as HG shows, simple logic will do this. However @DamonHD, in the first half of his paper, extends the HG simple analysis to a greater range of geometries and shows that the 'bad setback' effect applies in all (or almost all) cases. I think that the way to fix this, if you want 'unheated' rooms, is either to adjust the LSV so that the 'unheated' room is in fact heated but to (something like) the equilibrium temperature which would have been achieved had it not been heated (typically just a very few degrees below the temp of the adjacent room), or to have a type of TRV that does this without turning off (a sort of automatic lockshield). This would be a useful innovation IMHO.

For the reasons I explain above (which you don't appear to have countered) I don't currently think that the conclusions you have drawn in the paper you have pointed us to are valid. I stress that I may have misunderstand, however I do not see how you can claim (as I think you do) that operating TRVs in uninhabited rooms a way that causes the temperature of inhabited rooms to 'sag' shows that the setback of the uninhabited rooms 'saves money', when you have already shown that the same setup but where you dont allow the temperature of the inhabited rooms to 'sag' (almost?) always costs money. I think the latter results prove that the saving in the former is really attributable to the reduced temperature of the inhabited rooms, not to the setback in the uninhabited ones! Furthermore I think that making the statement that is made in the paper is potentially dangerously misleading to the casual reader. I apologise once more if I have misunderstood. However on your broader objective I think we agree wholeheartedly. I believe TRVs do have an important role to play but that their control mechanism needs to be completely redesigned to respond to the correct problems and to ensure that 'bad setback', TRV induced cycling and other potential pitfalls of micro-zoning cannot occur. I furthermore think that, in doing so, the analysis needs a lot of care and attention and, dare I say it, critical peer review (because this is a complex subject and its all too easy to go astray). It seems to me that TRVs (with the correct, probably interlinked, control mechanism) have the potential to solve the balancing problem, which installers simply dont have the time to do properly (or at all) the spatial setback problem, but in a way which does NOT cause bad setback (which I am pretty certain just involves 'turning down' the uninhabited rooms to around the temperature they would reach if turned off, but not actually turning them off the sizing problem (both radiators and system) if fitted before the install and suitably instrumented quite possibly several other problems I haven't listed To do this will require a rethink of TRVs as we know them. Adia, who you presumably know, are already doing something in this space. The good news is that the hardware already exists at least for an electronic implementation, more or less any 'smart trv' presumably has the right hardware. Once the ideas are proven it would however be interesting to challenge the hydronic companies to come up with hydronic (probably cheaper) solutions!

Can you please point out which results this conclusion refers to (where in the paper). As I read it the savings occur (in your model) only if you also accept a reduced temperature in the occupied rooms. I said this above and you didn't correct it, however I may have misread so I'd appreciate it if you could clarify. You are obviously enthusiastic about trvs. For transparency please confirm that you are not involved in any way with anything that benefits from the sale of trvs (or if you are please explain the involvement). I should add that I'm not anti trvs in heat pump systems (I have some!) but, so far as have so far seen, there is great potential for them to be misused to the detriment of running cost. In part this is because of the behaviours learned from fossil fuel systems, but these behaviours are pretty well embedded so there is a big risk that people get a bad (expensive) heat pump experience if trvs are widely deployed without very clear re-education.

Obviously you are right in principle. How much this matters in a real house where there is a fair amount of mixing between rooms is an interesting question. I have been surprised at how easy it turned out to 'balance' my downstairs radiators, which I'm pretty sure is not because they are perfectly sized but because adjacent rooms share heat. My house is basically square though, in a long thin house (or other square houses) it might be very different. My guess (but it's only a guess) is that a typical 2-3 bedroom house with tolerable external insulation may well behave as a single room per floor in practice.

For reasons to do with the history of my installation mine are similarly all over the place. In reality the downstairs pretty much evens itself out, undersized rads being offset by oversized ones in adjacent rooms, and the bedrooms upstairs are on trvs because they are way oversized and anyway we want them cooker (I will sometimes get round to trying to adjust the bedroom lockshields and ditch the trvs). The bathroom is, in principle, hopelessly undersized (we didn't change the towel rail), but I leave the door open to the hall and that, together with steam from the bath, deals with it. It all seems to work, based on four weeks so far of operation, and with much less fiddling than I had expected. It's a nice simple system, no hydronic separation nonsense, just heat pump connected to emitters and dhw via a diverter. I'm operating a couple of degrees less than the design flow temperature so happy with that too.

Ok I didn't describe it well. By 'right sized' I mean at design OAT, although a perfect WC curve will mean that they are also right sized at other oats (that's the point of WC after all). Of course rads will, in reality, be incorrectly sized to different degrees, that's where balancing comes in. However if they are all oversized once balanced it's better to turn down the WC than further to restrict the flows through all the radiators! If they are all undersized then you have to turn up the WC. Either way (In this correctly adjusted 'control') you end up with right sized rads at the operating ft (which may or may not be the design ft). As it's all a thought experiment you can just simplify this all down to correctly sized rads.

Quite so, but if all rads are oversized, which I think was the implied scenario, then better to turn the wc down. I think there is a lack of clarity in the discussion but you only get clarity by discussion so lets keep it going in the good natured way it is Agreed. To my mind if we are looking only for basic physics effects (or only modelling basic physics effects) in the steady state then the control, unless stated otherwise, is a system which is adjusted to achieve a specified indoor temperature 24x7 across the whole house in the most efficient way possible. With a heat pump this is a system where the balanced emitters are fed with water 24x7 at a temperature just sufficient to maintain the design IAT. From this starting point one can I think tease out the effects individually (for exanple) of zoning, time based setback or varying the target temperature . In the first two cases the control should be compared with a system which achieves the specified temperature in the non setback rooms or the non setback times (as applicable), not with one that achieves different temperatures in those rooms or times. In third case the control should be compared with a system which achieves the new target temperature 24x7 across the whole house. Each of these then teases out the effect of changing only one condition. Of course it's also valid to look at cases where more than one condition is changed, but that's a different set of questions, and if two conditions are changed then they must both figure in the description of the test being done. If we are lucky the effect of changing two conditions is, for sufficiently small changes, the sum of changing either individually, so we don't need to model all the combinations. That's my starter definition anyway.

I too am principally interested in retrofits, it's a purely amateur interest though. I also agree that comfort argues for some differentials, but maybe the differentials can be achieved without bad setback and without having a wc curve that is higher than it needs to be. My thinking here is that maintaining a level of background heating in the room where setback is desired is, primarily facing, better than turning it off altogether because you are increasing the total active emitter area and can thus operate at a lower ft.

I don't think that changes my mind. If rads are oversized then you can adjust the WC down until they aren't, thereby achieving greater savings than though zoning. If puree WC isn't used then you are sacrificing efficiency a different way and it's a different scenario altogether. Clearly there is a difficulty here in defining what the correct 'control' is, we may disagree or we may just not be clear enough. It's a really important thing to nail though and if there is any doubt (which there currently is) then it's important, I think, to state it as an assumption in any summary. In other threads real experiments are discussed often with inferences that are quite extreme. If we can't work out the control in a thought experiment, what chance does a real experiments have!

@DamonHD I read your paper with interest and like the simple physics based approach, which makes it understandable. I hope you and your colleagues are doing more of this, because we need it! I do have an concern with the interpretation of the conclusion however. In essence I think you confirm the 'bad setback' effect which can occur if a reasonably square/cubic house is only partly heated and which is described qualitatively on the heat geek website. You also explored a range of layout and oat variations and I think find bad setback in most. You then (I think) go on to show that if the occupants don't demand tight temperature control, the bad setback effect disappears and energy savings appear. So far so good. However not demanding 'tight temperature control' involves accepting that the occupied rooms reduce in temperature by up to just less than 2C and you assert that many will find that ok and thus part heating can deliver benefits. That may well be true but if it's acceptable to reduce the temperature by up to just less than 2C, even greater savings are to be had by turning the WC curve down a notch. Put another way if a 2C reduction is acceptable, the 'control' scenario is the scenario where that was the target temperature from the outset and with this as.a control the bad setback effect remains. I suppose you could argue that, if the WC curve can't be or isn't changed by the householder, then the original control is still the correct one, but this argues for a user friendly way to get WC right on the first place not a second rate substitute. Perhaps I have misinterpreted (and if I have please accept my apologies) but if not I think your paper confirms for a fair range of situations that heating only part of a (reasonably square/cubic) house is likely to lead to higher consumption assuming that you have WC adjusted to keep those rooms you need at or around whatever your target is. If so this is an extremely valuable confirmation of what heat geek describe somewhat qualitatively. Is there by any chance a similar paper dealing with temporal (as opposed to spatial) setback. If so can you post the reference?