Smart thermostatic radiator valves - z-wave

arachnoid

What is the current thinking on best smart thermostat products for home automation? I have OpenHAB and a z-wave network. I want to quickly get better control over heating (currently manual TRV's) by fitting smart valves. Integration to the OpenHAB network can come later. Boiler is Vaillant eco Tec Pro 28 (currently using a hard-wired Honeywell thermostat/timer). Radiator valves need to operate in both horizontal and vertical orientation. There are 9 radiators. Temp display on valves needs to be clear. Battery life should be good so not swapping too often.

xxGBHxx

Lots of options they're all overpriced and not worth it IMNSHO.

I've installed Tado, wish I hadn't bothered. It works (after some faffing about) and it does what I want but it's cost the best part of £700 and I doubt it's saved me more than £10 in reality.

The reality is someone in my family is in the house almost 24/7. The only time you get any value or benefit out of them is if you're regularly out of the house during the winter months so it can regulate the heating when you're not there. For me, working from home, it's almost completely worthless.

I've seen people recommend just about every system on here at one time or another. My Tado connects to my Hubitat hub without an issue so I can control it from there if I want. YMMV with Tado. You can get the generic Danfoss Z-Wave TRV's if you want to wroll your own or I think Heat Genius use rebadged Danfoss Z-Waves and have a fairly open API. I know some people swear by Honeywell but again YMMV.

Think long and hard about the real benefit you're going to get out of the system before you buy. It's a *VERY* expensive mistake if, like me, you realise after the fact it's a complete waste of time and money.

G

arachnoid

Thanks for the report on your experience.

The requirement includes maintaining temperatures for an elderly resident in part of the house (a studio) round the clock and part of downstairs during the day. Additionally, there is usually someone in another part of the house during the day. The property could be divided into three zones, e.g. studio, upstairs, downstairs, with more than one radiator in each zone. The whole house served by the same combi boiler. Electric heating (e.g. a small electric heater with a thermostat) could be used to supplement the main heating but I think that would soon cause the bills to rise.  

It's as much a requirement for comfort and well being as it is cost saving. Is there a half-way option, e.g. a nest unit and some smart valves that could be programmed to address some of the requirements?

neilball

If you want fully integrated, heat-demand driven control of the entire heating system then just some z-wave radiator actuators are not going to meet your requirements.

If you want decent battery life then systems like Honeywell Evo are worth a closer look - they achieve good battery life by keeping the radio electronics shut down most of the time in the battery powered devices, at the expense of using a proprietary wireless protocol. It gives you the option of using temperature sensors in the radiator actuators or paying extra for wall-mount sensors. It also controls the boiler (either switches control or using Opentherm if your boiler is compatible). It does have an App and access to an API via the could servers too. It also allows Alexa integration if you want that. It is self-learning/self-tuning (so learns the room thermal characteristics over time to improve accuracy of control) and also allows you to choose to use Optimum Start and/or Optimum Stop too.

xxGBHxx

Right so this is what I was saying.

A single combi boiler means it doesn't matter about zoning or anything as if there is ANYONE in the house it will likely fire the boiler to maintain heat in that part of the house regardless.

So think of it like this.

Zone 1 - Old person, temp min 21 degrees in house 24h day
Zone 2 - Working person min temp 19 degrees 8am-5.30pm
Zone 3 - Someone else temp 20 5.30pm-8am

Now think about how an intelligent zoning system would save money.

Regardless of which zone is triggered, the temperature of the water in the system will be heated to the exact same temperature (about 70 degrees). Between 8am and 5.30pm if Zones 1 or 2 fired, Zone 3 would not heat so you would save a very small amount for the radiators in Zone 3 not taking heat out of the system. Likewise, between 5.30 and 8am if Zones 1 or 3 triggered then Zone 2 wouldn't be taking heat out of the system.

But unless you have 10 radiators in each zone, this is a relatively small amount of additional heat/energy and probably amounts to a few minutes extra heating per cycle at most (I don't have the figures for it but I'm sure there is someone who could work it out) if anything at all.

The way I see it, the ONLY time a system like this saves any significant money (at least enough to recoup the £100's more it costs over normal TRV's) is where it's able to use geolocation to actively manage the heating throughout the house and where people are out of the house on an uneven and irregular pattern. The second you follow a regular pattern (everyone out of the house between 8-5.30) or where there is someone in the house 24/7 the additional benefit it get's you, while tangible is next to insignificant as that functionality can be met with a £80 thermostat and cheap TRV's.

Just decide on how much that comfort means to you financially and whether it's worth the outlay as I'm pretty certain money saving isn't going to be one of the drivers for your system.

The thought of ultra fine grained control of heating is great in concept and can even work out great in practice for specific circumstances but overall I think for many people it's an extravagance. As long as people buy it for what it is (comfort and convenience) rather than how they market it (money saving) then it can work out just fine.

G

neilball

But zoning does save money when you can control down to individual room level and only need to heat a few radiators at a time rather than the whole house. This means the heat loss from the radiators that are on is a fraction compared to heating the entire house, therefore you are only using a fraction of the energy at that point in time when using zoning. If the house is large, and the number of rooms in use at one time is low, then the savings will be significant. Even if all rooms are in use but controlled well (avoiding unnecessary overshoots) then this will save a moderate amount (remember the old adverts about tiring down your room thermostat one degree could save 10% from your heating bill?). The way your controls work for you may not be saving much, but that will not be the same for everyone.

arachnoid

OK. So if zones don't matter so much there are 10 rooms and I need control over 2 or 3 to maintain a stable temp during the day and more rooms at night. The main goal is stable temps in those rooms over saving money. At the moment the thermostat is in the lounge area (being the largest space) and I find it difficult to control temps in the target rooms via the thermostat in the lounge. Also, the manual valves in the other rooms are set according to temps required in the evening when the heating is on (they heat in the day too which is waste).  The system is as finely balanced as I can get it by manual tuning and I cannot go around adjusting several valves each day. The use of electric heating would I think add £200-£300 per year to the fuel bill. I can get Popp valves for around £50 and would not need these in e.g. the hallway or the bathrooms (where a minimum temp to keep the chill away is all that is needed). So I can probably get away with 6 or 7 smart valves and whatever is needed to interface to and control the boiler (what is that product please?). I need to be able to monitor and control heating when away from home (preferably via OpenHAB).  I think a spend of £500-£600 would pay back in 2 years or so vs increased electric bill. That would be satisfactory. Any savings beyond that due to not heating the other rooms would be a bonus.

xxGBHxx

I have a large house (4 bed detached) and I have 13 rooms with 18 radiators so I'm the poster child for this type of system. I have Tado set up with individual TRV's in each room and (currently) 8 "zones" (or rooms) that are all individually controlled. My house is not very economic (being 150 years old) so is not necessarily reflective of a new build with the amount of insulation they build into things these days. That said to balance out the lack of insulation somewhat my house is more suited to this kind of set up as I don't have any open plan and all the rooms are isolated and independent of each other.

What I find is that apart from the initial warm up in the morning the ongoing pattern of on/off doesn't and hasn't changed all that much even though I'm only heating a smaller number of rooms. I only heat the areas of the house I use during the day/night but with a brand new boiler which heats really efficiently to keep the rooms hot it only needs to be on a few minutes an hour.

Now I'm going to be very generic here but looking at the Energy Saving Trust website, by installing a programmer, room thermostat and thermostatic radiator valves you save £80 a year in a typical 3 bed semi. There's no figures on smart control specifically but Tado and Scottish Energy have their own ridiculous claims of saving anything between £180 and £250 a year. However as Which points out that's based on huge assumptions like the fact you have your heating on 24/7 before and that you have no pre-existing controls. Hive even admit that under certain conditions (such as only having your existing heating coming on 1-2h a day) Hive will cost you MORE money.

The problem with your statements are you're comparing a smart system to nothing at all. In that case it is, of course, much better. But I could put TRV's on every radiator for £5 each (or 20 if I want to splash out on Draytons) and £80 on a good thermostat/controller and get much of the same savings. I lose much of the convenience and some of the fine grain control of course but I don't lose much of the financial benefit. As long as I can remember to manually adjust the TRV's when I need to then most of the benefits come from that.

So coming back to what I said above, if your main concern and driver is convenience and remote control, sure, the likes of Tado fit the bill. If your only concern is saving money then you'd be far better off with cheap TRV's and cheap, generic room thermostats/controllers as at worst you're not ever going to recoup the cost of installing a smart system and at best it's going to take you years to see any financial benefit.

G

neilball

We’ll have to agree to disagree - I work in the HVAC controls industry and have seen first hand what energy savings can be achieved with appropriate technologies installed well. I’ve worked almost exclusively on residential control systems for the last 20 years or so, and seen installs of all sizes. Some do just what you say, give much improved comfort and individual room control but don’t save a huge amount simply because the heating was already reasonably well controlled, but the upgrade gave much easier management and accuracy for the owners. Others installs have made quite large savings - usually in large houses previously without any zoning, where the new controls allow unused parts of the house to be kept at a setback temperature, and other rooms heated to preferred comfort levels when they are used, rather than everything being on or off. I’ve seen savings here of between 25-60%, and for large houses with large heating bills this is significant and offers a real payback (generally somewhere between 5-10 years, so not a short term payback).

I also see plenty of very large installs where the costs of the controls will never be recovered from energy savings, but the houses would need a sophisticated solution any, but hopefully without the complexity of a commercial grade BMS system (often with several heat sources for each room, heating and cooling to manage, multiple heat/cool sources in the plantrooms, which are full commercial grade installations). Here the costs would seem astronomic compared to that spent on more typical houses, but using the likes of Evo for the room-side controls often means costs are significantly cheaper than a full blown BMS would otherwise be (and remain usable by the majority of home owners). My largest houses to date have somewhere close to 190 separate room-side heating zones, and still used the Honeywell room-side controls that could make up any standard Evo install (but obviously an awful lot of it!).

sirkuk

I run a Drayton Wiser setup in my house with a Wiser thermostat on each radiator in the house. It is essentially a cheaper equivalent of the Honeywell Evo system (I'm not sure how it compares to Tado) and I have no regrets.

Apologies if I am stating the obvious to you but from the quick glance at the messages above and for further substance to the argument of TRVs vs smart heating, it falls into the category of convenience as it is in essence automating the action of you manually adjusting all of the TRV valves in your house throughout the day to suit whatever temperature you want at that moment in time (say turning your bedroom radiator TRV up before bed so the room is warm in the morning but then turning it down in the morning so you don't unnecessarily heat the room through out the day - for example). However, what sets it apart from manual TRVs is that any room in the house can call for heat and every room in the house has its own heating schedule so I can vary the temperature in each room throughout the day rather than a call for heat command coming from a central thermostat in the hallway. Plus, I don't have to manually fiddle with TRVs at certain times in the day to adjust the temperature accordingly if I was that was inclined to avoid unnecessarily heating vacant rooms (which, to be honest, I don't have the time or motivation to do). As a result, I'd say my heating bills have gone down by using the Wiser system and I can view the real time temperature in each room from my phone. As a cost saving exercise though, it is going to take some time to recoup the cost of the system but the convenience alone and more precisely controlling the temperatures throughout the house is worth it to me.

The Drayton Wiser system doesn't tick all of your boxes as there's no temp display on the valves and nor is it Z-Wave but it does have an OpenHAB binding.