Heatgeek website

[JamesPa]

6 minutes ago, DamonHD said:

Because one curve for the whole home is clearly insufficient at some level when the heat losses and gains of rooms relative to one another is changing.

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.

[marshian]

3 hours ago, DamonHD said:

Because one curve for the whole home is clearly insufficient at some level when the heat losses and gains of rooms relative to one another is changing.

 

Isn't that where you have to accept it as a compromise? I don't want perfection and I can tolerate swings of less than 1 deg (well I say tolerate but what I mean is I can't notice them)

 

I get a small amount of solar gain in Winter in 4 rooms (2 bedrooms, Dining room and Living room) - if the impact  warms the room up beyond the TRV set point the rad gets shut down.

 

I'm only running my TRV's now as limiters set approx 0.5 deg above the target room temp.

 

My room to room heat transfer is minimal as the majority of rooms are heated 24/7 (OK to slightly different temps but with say one bedroom at 18 deg next to a bathroom at 21 the delta between them is just 3 deg - there isn't going to be a huge movement with a delta of that size. Heat loss calcs said 22 w gained by bedroom and 64 w lost from bathroom.

[DamonHD]

1) The static calcs I did in the model in my paper suggested very significant energy savings by doing TRVs right, which back up my experience.

 

2) Dynamic response to occupancy is another significant saving, eg heating unoccupied bedrooms during the day even if people are home all day.  Again, reinforces what I saw in substantial trials.

 

3) Given how cheap and easy to use TRVs are (~1% of the rest of the heating system ish) and can save 10--30% of consumption and footprint for <2Y financial payback, never mind comfort, why NOT put them in by default, even if you leave them a bit high if in doubt and lean on WC as much as possible?

[marshian]

16 minutes ago, DamonHD said:

1) The static calcs I did in the model in my paper suggested very significant energy savings by doing TRVs right, which back up my experience.

 

2) Dynamic response to occupancy is another significant saving, eg heating unoccupied bedrooms during the day even if people are home all day.  Again, reinforces what I saw in substantial trials.

 

3) Given how cheap and easy to use TRVs are (~1% of the rest of the heating system ish) and can save 10--30% of consumption and footprint for <2Y financial payback, never mind comfort, why NOT put them in by default, even if you leave them a bit high if in doubt and lean on WC as much as possible?

 

I have 13 rads - all have TRV's

 

What you describe in terms of leaning on the WC and using the TRV's as temp limiters is exactly what I am doing

 

This is the dining room showing a little solar gain this morning

 

 

If it his the temp target the TRV will reduce the flow to stop overshoot

 

The dip and recovery was due to water heating stopping the CH for 21 mins (PDHW setup)

[JamesPa]

7 hours ago, DamonHD said:

1) The static calcs I did in the model in my paper suggested very significant energy savings by doing TRVs right, which back up my experience.

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.

Edited Thursday at 21:10 by JamesPa

[marshian]

18 minutes ago, JamesPa said:

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 think for me there is an educational step missing in the industry, the manufacturers, Installers and the end users

 

Go back to before TRV's were a thing - your control over the rad was a valve that could be opened or closed at one end

 

You didn't use it to trim room temps unless you had to because the result the next day could be the opposite so as a result most of the time there was an element of "overheating"

 

Then TRV's come along with their fancy numbered scale and all of a sudden room temp could be set or trimmed with some degree of repeatability - as a result energy saving - trouble is if one TRV in one room works well then fitting them to all rooms must be 100 times better

 

Then system becomes over zoned and cycling screws up the boiler efficiency but as you are already saving energy a little loss here doesn't hurt right??

 

Then comes along "smart" TRV's - they aren't really smart as such they just have a better level of control than the old waxstat variety and they can really screw with boiler efficiency because these TRV's can call for the boiler to fire............ Yes one room drops below the setback temp and the boiler fires up running a circuit size of maybe as little as 30 litres so burns are super short but the room temp is recovered

 

Now fit a house with a bunch of those and you can have all the rooms individually calling for heat at different times - I've been there with Wiser - 8 hrs overnight 53 boiler fires - fifty bloody three times in 8 sodding hours!!!!

 

TRV's have a place but it needs to be a place of "balance and control" and people need to seriously consider a strategy for their implementation, operation and level of control they are allowed.

 

Manufacturers want to promote what they sell TRV's Good - More TRV's better - Smart TRV's must be better than "dumb" TRV's therefore more smart TRV's must be even better when in real life too much of anything can be bad.

 

Installers need to explain the risks of over zoning and giving smart things control of dumb things.............

 

99.9 % of the "General Public" are not going to have the understanding needed to make even a remotely educated call

 

JM2pW

 

PS I know 2/10 bloody poor rant and lack of variety in expletives

 

 

[marshian]

1 hour ago, JamesPa said:

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.

 

I missed this edit because I quoted before you'd added it but can I just say I 100% agree with this - I think my long reply says pretty much same thing

 

TRV's can save energy but badly used they can drive up energy usage and smart ones can do far more damage whilst apparently being sold as the next best thing.

[joth]

 

9 hours ago, JamesPa said:

 

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 believe DamonHD is the founder of  OpenTRV

https://www.theregister.com/2014/08/25/doing_my_own_ting_making_money_from_a_startup/

[marshian]

34 minutes ago, joth said:

 

I believe DamonHD is the founder of  OpenTRV

https://www.theregister.com/2014/08/25/doing_my_own_ting_making_money_from_a_startup/

I freaking love the internet for stuff like that - well found sir

 

It certainly clarifies the position

[DamonHD]

I say in the paper that I spent a decade inventing a smart TRV (and bringing a commercial version to market). There are now ~500k Radbots out there.  I have views on TRVs, and I am eating my own dogfood at home, but I have no commerical involvement with Radbot any more.

 

AND I am hoping during my PhD to fill some (huge) gaps in the academic literature about TRVs and in particular interactions with heat pumps, and some of that research may be funded by manufacturers because everyone would really like to know!

 

My aim and thesis working title is "Improving UK home heating decarbonisation".  I suspect that that will involve TRVs for reasons that I have laboured in this thread and elsewhere, but if TRVs aren't part of the answer then no problem.  I shall find out what else is.

 

My PhD research plans:

 

https://www.earth.org.uk/img/research/20240917-PhD-confirmation/confirmation.pdf

Edited Friday at 11:33 by DamonHD

[DamonHD]

14 hours ago, JamesPa said:

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.

AND if you are running open loop weather compensation yes.  But I also point out that a small degree of feedback and loop closing may retain the electricity savings that you'd expect from the heat savings, and mitigate sag somewhat - I did not attempt to calculate how much.

[marshian]

6 minutes ago, DamonHD said:

I say in the paper that I spent a decade inventing a smart TRV (and bringing a commercial version to market). There are now ~500k Radbots out there.  I have views on TRVs, and I am eating my own dogfood at home, but I have no commerical involvement with Radbot any more.

29.9 million homes in the UK majority using water based heating systems - for shits and giggles lets say average number of rads per home 6

 

500,000 radbots (Never heard of them but google educated me) so a market penetration of less than 1%

 

I'm not sure why you would be eating your own dog food - strikes me as petulant comment adding nothing to the discussion which was going rather well I though as a pro's and con's of TRV's

 

I'm 100% OK with your views on TRV's but I'd hope you can understand that there are ways in which they can drive up energy usage.

[DamonHD]

"Eating your own dogfood" is a standard term in the start up world and beyond, meaning that you actually use (and understand and stand by) your own product, which is IMHO the right thing to do.  Far from petulant.

 

I estimate ~100M rads in UK homes, ~1B in European homes, and about the same again in commercial properties.

 

There are ways of misusing all tools.  Most UK home heating systems are vastly oversized and fairly poorly installed and understood and used I believe.  The minimum power output of my gas combi was more than double the maximum heating demand on the coldest days, so it spent all its time cycling regardless of TRVs.  And the expansion vessel failure rate was only beaten by the diverter valve.

 

My new heat pump seems somewhat better matched to heat demand, though was the smallest one that Octopus could do AFAIK.

Edited Friday at 11:54 by DamonHD

[marshian]

7 minutes ago, DamonHD said:

"Eating your own dogfood" is a standard term in the start up world and beyond, meaning that you actually use (and understand and stand by) your own product, which is IMHO the right thing to do.  Far from petulant.

 

Thanks for that explanation - it's an expression I've never heard of and it didn't translate well without the background

 

7 minutes ago, DamonHD said:

I estimate ~100M rads in UK homes, ~1B in European homes, and about the same again in commercial properties.

 

My rough calcs of radbots market penetration wasn't far off

 

I wonder how many smart TRV's (accross all the manufacturers) have been sold - They are quite an expensive purchase

 

7 minutes ago, DamonHD said:

There are ways of misusing all tools.  Most UK home heating systems are vastly oversized and fairly poorly installed and understood and used I believe.  The minimum power output of my gas combi was more than double the maximum heating demand on the coldest days, so it spent all its time cycling regardless of TRVs.  And the expansion vessel failure rate was only beaten by the diverter valve.

 

Ahh the "energy saving" combi boiler where water heating demand means hang the biggest kW white box on the wall that has a piss poor modulation rate so totally unsuitable for space heating without cycling but saving on water right??

 

Crazy situation promoted by industry with a lack of education in installers and homeowners.

 

7 minutes ago, DamonHD said:

My new heat pump seems somewhat better matched to heat demand, though was the smallest one that Octopus could do AFAIK.

 

In my view we've learnt something from the combi process but unfortunately I don't believe the UK is fully prepared for ASHP introduction - I don't believe the grant process is helping either - it's just inflating the cost of the change from gas to electric

 

[DamonHD]

25 minutes ago, marshian said:

In my view we've learnt something from the combi process but unfortunately I don't believe the UK is fully prepared for ASHP introduction ...

 

I agree, which is why I'm doing my research, to see if there are any wheels that I can find to grease...

[DamonHD]

FWIW my own live-ish TRV percentage-open chart (for most of the rads):

 

 

and call for space heat:

 

 

Note that there is currently a problem with this system and it hasn't been fully commissioned (or paid for!) yet, and I am continuing to tweak as householder and researcher.

 

So have a good laugh!  B^>

Edited Friday at 12:54 by DamonHD

[JamesPa]

10 hours ago, DamonHD said:

My aim and thesis working title is "Improving UK home heating decarbonisation".  I suspect that that will involve TRVs for reasons that I have laboured in this thread and elsewhere, but if TRVs aren't part of the answer then no problem.  I shall find out what else is.

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!

Edited Friday at 21:59 by JamesPa

[JohnMo]

Trouble with any devise that makes a room colder when no one is present, just stays that way in a low temperature heating system. If you have flow temps anywhere near correct, you have either long left the room or fallen asleep waiting under the blanket you covered yourself with, to keep warm, before the room reheats.

 

Energy usage will be lower, your house is just colder also.

[DamonHD]

@JamesPa I hear what you say and I shall think about it: thank you for tussling with this.

 

But where you say "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!" taken literally and simplistically is untrue: it is a simple matter of physics that all internal spaces that are at a lower temperature than they otherwise would be lose heat to outside more slowly than they otherwise would, and thus reduce heat demand, and where WC is in use that reduces electricity demand and thus cost.

 

Note that the initial HG claim being countered was that reduced heat demand could cause increased electricity demand, which is again simply not true with use of plain open loop WC.  Whether that arrangement is acceptable for other reasons, some of which we have discussed in this thread, is a separate issue.

[JohnMo]

3 minutes ago, DamonHD said:

Note that the initial HG claim being countered was that reduced heat demand could cause increased electricity demand, which is again simply not true with use of plain open loop WC.  Whether that arrangement is acceptable for other reasons, some of which we have discussed in this thread, is a separate issue.

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.

[DamonHD]

But plain WC does not increase flow temperature in response to anything other than falling outside temperatures.  If you are saying that someone might shift the whole WC curve up then that is a different matter which I address as "fiddling with the settings".  Notionally that WC curve is *computed* from the heat loss calcs at installation time and left alone.  😀

[marshian]

3 minutes ago, DamonHD said:

But plain WC does not increase flow temperature in response to anything other than falling outside temperatures.

 

Agreed

 

3 minutes ago, DamonHD said:

If you are saying that someone might shift the whole WC curve up then that is a different matter which I address as "fiddling with the settings".  Notionally that WC curve is *computed* from the heat loss calcs at installation time and left alone.  😀

 

If I'd have left my WC settings as the gas engineer set it up I'd be forever bouncing of the TRV limits

 

1.4 was the initial set point at 20 Deg Target Room Temp (Not measured)

 

I'm now on 0.5 at 20 Deg Target Room Temp

 

I do have an easy way of compensating for room factors - the boiler Target Room temp can be adjusted from 3 Deg C to 30 Deg C

 

Changing that by one or two degrees either way has a significant effect on flow temp and it changes the WC curve

[JamesPa]

39 minutes ago, DamonHD said:

But plain WC does not increase flow temperature in response to anything other than falling outside temperatures.  If you are saying that someone might shift the whole WC curve up then that is a different matter which I address as "fiddling with the settings".  Notionally that WC curve is *computed* from the heat loss calcs at installation time and left alone.  😀

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.  

 

1 hour ago, JohnMo said:

1 hour ago, DamonHD said:

Note that the initial HG claim being countered was that reduced heat demand could cause increased electricity demand, which is again simply not true with use of plain open loop WC.  Whether that arrangement is acceptable for other reasons, some of which we have discussed in this thread, is a separate issue.

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.

Edited Saturday at 09:58 by JamesPa

[JamesPa]

@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.

Edited Saturday at 10:15 by JamesPa

[JamesPa]

1 hour ago, DamonHD said:

@JamesPa I hear what you say and I shall think about it: thank you for tussling with this.

 

But where you say "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!" taken literally and simplistically is untrue: it is a simple matter of physics that all internal spaces that are at a lower temperature than they otherwise would be lose heat to outside more slowly than they otherwise would, and thus reduce heat demand, and where WC is in use that reduces electricity demand and thus cost.

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).