Smart Heating Controls - My Experience with Honeywell Evohome - Part 2: More Technical Points

During lockdown in 2020 it seemed like a good idea to get better control of our heating. My focus was better comfort, but saving energy would also be good. We had Evohome installed in September 2020.

 

So, with the perspective of 3.5 years after installation (March 2024), how has the system performed?

 

This is part 2 of this review. I posted part 1 in January, targetting user experience and this Part 2 is focussed on more technical points.

 

Selection & Installation

• The Automatic Bypass Valve (ABV) allows all radiators to have Evohome TRVs. It is a short copper pipe and valve added close to the boiler to allow for pressure release when the last radiator turns off and allow time for the boiler to turn off).

Automatic Bypass Valve (ABV) installed just under the boiler.

 

Early installation issues fixed by the installer during September and October:

• A couple of the TRVs did not operate correctly to start with - not sure why (maybe sprocket not engaged with the valve on one?)
• Hot water tank thermostat incorrectly installed (it turns out that the recommended installer had so far installed just 6 Evohome systems and that ours was their first with a thermostat for the hot water tank) - this was also fixed in a couple of visits.
• We had a pre-existing wiring fault; this took more extensive diagnostic work and much head scratching from Mike the installation engineer. He stuck with it and found the cause; a broken cable core between hot water tank and boiler.  I laid in a replacement cable (floor boards up, hole in the ceiling, etc) and he connected the cable at each end.

Installation result:

• From the installation starting in mid-September and finishing at the end of October we had a stable system ready for winter:
• Without the existing wiring fault I would not have needed the installer to return more than a couple of times.
• There were gremlins with the system, over the September/October period, that I fixed myself (eg valves that lost their calibration/off position).
• I agreed with the installer a fair split in costs for the extra work that was not included in the fixed price (the broken cable core was our cost, the rest was theirs)

 

Lessons learned (more technical points)

• The Honeywell documentation is OK for a working system but very limited on fault diagnosis and resolution. There is limited 3rd party material available online. So, learn what you can when the installer is on site.
• Testing the system can be frustrating. The time lag from changing a temperature setting can be from a few seconds to a few minutes as the change ripples through from TRV to app (or app to TRV) and then to boiler. This has never been an issue in day to day operation, but means that testing can take a long time and needs much patience . I am sure that there were a number of times I suspected a fault, but waiting a little longer would have proven that everything was working (see above on knocked confidence).
• I would recommend having a simple test script - eg
1. start with central heating off.
2. Check all radiators cold
3. Turn all radiators to target temperatures above the actual room temperature (eg +2deg) using the app, so that all radiators should come on:
• Wait 20mins (this probably only needs to be 5mins, but you want to be certain that it is not a time lag issue)
• Check each TRV has the new target temperature reading
• Check each radiator is warming up
• If the TRV has the right target temperature but the radiator is cold you can check the actual demand on each TRV on 'system summary' on the handheld display (press 'settings' for a few seconds and you get the option to go to the 'configuration' menu).
4. Turn all radiators off from the app:
• Test as above, but this time you have to wait longer for the radiators to cool down.
• A test script is useful because:
• You quickly identify faults with high level of certainty.
• It helps in removing any gremlins early.
• If there is a fault you can be very specific with the installer on what is wrong and confidently replicate the issue when they visit and then test that the fix has worked.

 

Evohome Software - Deficiencies and Recommendations for Honeywell

While software is pretty easy to use it does have a few (minor) deficiencies/frustrations:

• I have not seen any software updates. In writing this piece I have googled this point and I see that there has been an 'application software' update (mine is v02.00.17.03 and a May 2023 posting on the manufacturer's website has v02.00.19.33 - see https://resideo.my.site.com/ensupport/s/article/How-to-check-the-firmware-on-the-evohome-WIFI-controller?language=en_US). There is very little written about what the update does, other than it 'works on heat pumps' and has 'smart weather features'. I had registered my e-mail address, but Honeywell did not bother to contact me to tell me about the update. Apparently the update should be automatic, but you can also send your MAC address to Honeywell (now Resideo) and they will update the firmware (I have just tried this and the webform kept crashing - I will keep trying in the coming days and update this article if I get a result)...

...so perhaps all that follows is now out of date with the new version of software!

• While programming a new schedule is reasonably simple, it is also a little fiddly. It is Perhaps hard to see how to make it less fiddly on the Evohome controller with such a small display. Perhaps there is a case for a PC / iPad version of the software with a simpler drag and drop scheduling interface (there is a web interface - this seems like a simplified version of the hand controller and does not include a schedule editor)
• The handset and phone apps have different interfaces. Not sure why Honeywell went to the effort of developing 2 interfaces and putting all of their users to the added effort.

Hand controller scheduling interface	Hand controller temperature override interface
iPhone scheduling interface	iPhone temperature override interface

• The 'System Summary' screen is pretty useful in diagnosing issues - showing the %age demand on each radiator; it seems odd that it is buried on the configuration menu.
• I have not tried the 'optimum start' and 'optimum stop' features.
• I do think that these are a great idea  - Evohome learns the warm up / cool down profile of your home/room and you schedule the time at target temperature as opposed to the heating off/on times. In other words Evohome turns the heating on early on a cold winter's day so that when you get up the house is warm; on warmer days the heating comes on later saving you money.
• So why not use them? Given the initial 'teething problems' this seemed just another layer of complexity to go wrong; I wanted to build confidence in a stable system. I must admit that during the last couple of years I have pretty much forgotten about Evohome (which is what I wanted) and I have not got around to trying this feature. Writing this has got me interested again (I feel an experiment and another blog post coming).

 

After all the above 'negative points' I reiterate the point from part 1: The Evohome software is easy to use and fine for day to day operation. However, I do think that Honeywell has missed an opportunity and a few extra software features that would improve the value of the system:

• Self guided fault diagnostics / resolution (eg my low cost HP printer has great animations for replacing ink cartridges and all the faults that I have encountered over several years)
• Build in more fault tolerance (eg a monthly automatic TRV calibrate cycle and a proper battery warning on the hot water thermostat would probably eliminate >90% of the issues that I have seen)
• Better controls on going out / turning the heating off/down (Eco mode):
• Resolution of <days><hours><minutes> on when to switch the heating back on
• Include the option of hot water off and a check box to have this on, say, 24hours before the heating is on (I have the hot water scheduled just once per day and want to return from holiday with hot water in the tank)
• Checkbox option for 'optimum start' so that Evohome works out when to put the heating on for my expected return time, even if I am not using optimum start at other times.
• I see that other systems have 'geofencing', so that your mobile phone instructs the system when to turn on based on your phone's location. I have not used such a system, but my view is that this feature would be bad:
• My distance from home is not a good indicator for how long I will be away (eg 5 miles walk to a local pub and a boozy afternoon by a log fire Vs 10 miles to a shop and back in 2 hours)
• How does the system decide how to arbitrate between 2 or more phone? (& not an easy algorithm as my wife often does not carry her phone with her, especially if I have mine).
• If the flow temperature is set low (good for boiler efficiency) then the warm up time, from cold, may be several hours. In other words geofencing would have to work with an 'optimum start' algorithm. If you were away for more than a few hours and you drove home at 70mph then the 'geofence' would need to be set at a few hundred miles away - is this really practical? If you fly home then it relies on the efficiency of your local airport - for me landing at our local airport to home is usually about 2 hours, ie the house would not be warm after a week away in Tenerife in the winter and the geofence was set at the airport.
• 'System Summary' screen is pretty useful in diagnosing issues, this should be more easily available  - I do not understand why this is buried on a hidden page on the hand held display and not available on the phone app.
• The schedule has a limit of 6-temperature changes each day - see part 1 on how we use the system - it would be better to have more.
• PC / Web version of the application software for easier schedule setting.
• Having a few labelled schedules (eg on the PC interface) would probably be useful (holidays, winter, summer, visitors staying, etc) - the system currently allows just one additional stored schedule.
• Data logging:
• good for diagnosing Evohome faults (log target and measured temperature)
• Helping to assess where the heating is working hardest (log target temperature, TRV demand and measured temperature). I think that this would help show where insulation would have the biggest impact and/or if a radiator is undersized.
• Synchronised demand. I have a theory that Evohome is turning the boiler off and on more times than is required and that this is wasting energy. This is just a theory and clearly depends on the boiler and my knowledge of boilers is almost zero...

...Just say that Evohome switches on radiator A  and the room with radiator B is at temperature and so the TRV is off. This will fire up the boiler. A little later room A gets to temperature and so the TRV on radiator A switches off. The boiler now turns off. A little later, the same happens with radiator B so the boiler is on again. Is there an opportunity to optimise this so that when the boiler fires up because radiator A is demanding more heat then the system checks for any other radiators that will need heat in the next, say, 30 to 60mins and turns on these TRV's (perhaps at a low %age demand) to give (some of) this heat early when the boiler is on anyway. I am not sure if this would save energy and I guess that it all depends on the current Evohome algorithm and boiler efficiency characteristics.

• I think that Evohome has the data to be able to provide a measure of insulation. I have seen figures quoted for insulation quality in terms of 'temperature loss in 5hours from 20degC inside when 0degC outside' (https://www.euronews.com/green/2022/12/09/europes-energy-crisis-in-data-which-countries-have-the-best-and-worst-insulated-homes). Since installing Evohome I have also put in some additional insulation - it would be really cool if Evohome could tell me if this has had an impact and how my home stacks up against others in the UK and elsewhere.

 

My view of Evohome after 3 Years

• Comfort: Evohome gives a much more consistent and controllable temperature through the house than our previous setup (ie thermostat in the hall, programmable timer and mechanical TRVs). The following are minor points in comparison to the previous set up.
• Our Kitchen temperature is not very even across the room; I think because the radiator and thermostat/TRV is behind a breakfast bar & there is limited air circulation with the rest of the room. The fact that we worry about this, & this was the case before we installed Evohome, tells you that we are getting to the finer points of getting good temperature control. I may experiment with a separate Evohome room thermostat, located elsewhere in the Kitchen.
• We have our flow temperature set at 65degC. I understand that a lower flow temperature would make our condensing boiler run more efficiently. However:
• As the boiler also heats our hot water tank we need a 65+degC flow temperature to avoid bacteria growing in the hot water tank.
• Our boiler model can achieve this with a weather compensation add on, but this means that the flow temperature will vary during the day. Question: will the Evohome self learning algorithms cope with an ever changing flow temperature? (see future blog post on weather compensation)
• Reliability:
• After the first couple of months I learnt how to fix the occasional (every few months), and undocumented, TRV fault and I now believe that, outside of battery failure, this is the only TRV fault that I have ever seen:
• TRV and physical valve being out of sync (eg radiator valve is off and the TRV 'thinks' that it has turned it on).
• I have not found any online guide as to how to fix this, but the following is quick and seems to work:
• Turn the TRV to +5degC and wait for the TRV to finish attempting to turn off the radiator (ie after any motor whirr has completed).
• Unlock and remove the Evohome TRV (slider the bottom of the TRV)
• With the TRV removed, manually turn the valve off (black knob/sprocket on top of the valve, that engages with the TRV) until you feel strong resistance, without forcing it)
• Replace the TRV and lock.
• Turn up the TRV to a high (radiator on) target temperature:
• The TRV will start to whirr and switch on demand (within a few seconds)
• Often, but no always, the TRV display then shows "CYCL" and, I think that, this indicates that the TRV is self-calibrating (ie finding the max on and max off end of travel for the valve). After cycling for a while (1 minute?) the TRV then goes to the set temperature.
• Hand held display battery life is a pain, especially when doing fault diagnosis. It would be good to be able to carry the handheld device from radiator to radiator to check demand against radiator temperature. The handheld display battery life does not allow for this, lasting only a few minutes.

 

Final Comments:

I would recommend Evohome if you want to control individual room temperatures and you are not a technophobe. With a few developments and better support materials, I think that Honeywell/Resideo could make this a more robust system suited to a much wider market.

Insulating Pipes in the Garage

We had a new condensing boiler installed in Summer 2017, complete with new radiators and connecting pipes. The new connecting pipes are mostly plastic and, to simplify installation, the garage was used to route some of the pipes. My simplistic take is that the other pipework, mostly in the ground floor ceiling (and a little on internal walls or behind skirting boards), is helping to warm the house and so the fact that it is not insulated does not really cause significant losses. However, the pipework in the garage, was simply raising the temperature of the garage.

 

Situation before insulation:

Pipework routed through the garage: 

• 13.8m of 28mm  diameter pipework
• 2.3m of 15mm  diameter pipework
• 8.4m of 10mm diameter pipework

When hot water was flowing to these radiators the pipework was hot to touch. 

 

After insulation:

28mm Pipes with Insulation	10mm Pipes with Insulation

 

The external surface of the insulation is very slightly warm to touch when water is flowing to the radiators. I would expect that the radiator temperature is a little warmer now, but I could not detect this by hand.

 

Shopping list:

• 2x 3pack x 2m of 9mm thick insulation for 10mm diameter pipes. Note: most insulation that I found for smaller pipes was thinner than for larger diameter pipes; I am not sure why given that the physics, I think, is the same. I chose the thickest that I could find.
• 13mm thick insulation for 15mm diameter pipes.
• 19mm thick insulation for 28mm diameter pipes.
• Pipe clips (new ones to allow space between pipes & the wall for insulation)
  
• Spacer/washers: the pipe clips for smaller pipes, did not allow enough space for insulation at the back, so spacers were requires so that the pipe sat a few extra mm from the wall).
• Duck tape (to hold smaller pieces of insulation, eg at corners and joins)
• Total Approx £120

 

Doing the work:

This took a total of about 10 hours at the weekends, mostly in replacing the pipe clips to give space for insulation behind the pipes - better insulation and the insulation holds on the pipe without (much) tape.

 

Estimate of saving and payback:

This is hard. This was the only new energy saving measure that I took before the winter of 2021/22 and in 2021/22 we saw a 36% (£980) saving in gas usage over 2020/21. However, I am not convinced that insulating a few pipes gave all of this saving. Perhaps lockdown during the pandemic causes a spike in usage in 2020/21 or 2021/22 is unusually low and usage will rise back up in 2022/23...

...I will analyse the data for 2022/23 and see if I can get a better understanding of the energy saved and payback over a longer period (future blog post). However, given the low cost and the dramatic drop in pipe temperature, I would be surprised if payback is very long.

 

Can I Calculate the Energy Saving?

This website  (https://modbs.co.uk/news/fullstory.php/aid/615/Clear_thinking_on_insulating_plastic_pipes.html>) gives a range for the heat conductivity of plastic pipe of 0.16 to 0.22 W/m.K. I am a little dubious about this as heat loss is surely related to surface area and my pipes range from 28mm diameter down to 10mm diameter, so must have a surface area range of around 3:1. However, using an average of:

• 0.2W/m.K for all pipes (irrespective of diameter)

and assuming:

• Uninsulated: a temperature drop of 60degC across the plastic pipe wall, from flow temperature (set at 70degC) to average room temperature (guessed at 10degC)
• Insulated: zero temperature drop on the plastic pipe wall (ie all the temperature drop is across the insulation)
• Gives a total saving in heat/power loss of ~300W, when the pipes are hot

I mapped this across the year with the following assumptions:

• Heating on from 6am to 10pm = 16 hours (some days we keep it on later, but we also turn it off when out)
• Duty cycle (& this is a real guess) of 50% in winter (4 months), 25% in Spring/Autumn (2months+2months), 10% in summer (4months)

Gives an annual saving of approx. 500kWh, or ~£35, at the £0.07/kWh charge that I am using from August 2023.

Given how hot the pipes were then I can believe the 300W (1/3 of a 1 bar fire). However, given all the assumptions I think that there is quite an error band in this calculation, especially in the average pipe thermal conductivity and the duty cycle that I used to map this onto annual energy savings.

 

And Finally:

In writing this post I have realised that the pipework for the hot water cylinder is all under the 1st floor boards (above the ground floor ceiling). Perhaps there would be a case to insulate these pipes as they heat up the house in summer (a future project and blog entry perhaps).

 

 

Insulate the Attic

Introduction:

 

 In summer 2022 energy prices were shooting up. Various websites highlight this as one of the fastest payback and high impact jobs to improve house insulation (eg  https://energysavingtrust.org.uk/advice/roof-and-loft-insulation/) ...

...my only worries were our existing floorboards and attic junk making this a big job. I also worried about the likelihood that everyone else had the same idea and there would be a global shortage of insulating materials.

 

What we had before:

• Approx 100mm of insulation, made up of:
• Central portion of attic (below floor boards) - Kingspan (this has approximately 2x the insulation properties of regular fibre insulation, given the same thickness)
• Approx 100mm of very old fibre type insulation

 

What I added:

• Insulation: "itch free" (https://naturalinsulations.co.uk/product/supasoft-insulation/ ). This was placed on top of the existing insulation to get approx 300mm across the whole attic.
• Loft Stilts (https://www.loftstilts.co.uk/). It is only afterwards that I have realised that there are multiple brands (eg Loft Legs) doing a similar job; I did not do any comparisons before purchase.
• I also needed some screws for the loft stilts, but everything else was existing (floor boards in central portion of attic, large access hatch, lighting, etc)
• Costs:
• Insulation: £1,015 (including shipping)
• Loft Stilts:     £145
• Total:         £1,160

 

The Plan:

• Clear out junk from the attic (hired a small skip)
• Move remaining stored stuff to one end of the attic
• Lift floor boards at the other end
• Add loft legs
• Add insulation - now around 300mm across the attic
• Replace floor boards

One end of the attic complete (you can see attic junk at the edge of the picture)

 

• Move 50% of stuff from one end to the other
• Lift floor boards in the centre, etc
• Move 100% of the stuff to the completed end
• Repeat process on final end
• Re-distribute stored stuff

 

Execution:

• Looking online it seems to be simply a matter or rolling out the insulation. It is all the other things that take the effort and a bigger job than I had at first envisaged
• It was hot and sticky work (Sept/Oct):
• How long did it take? - hard to judge as I did the work at weekends over a few weeks and did not work every day. The work took about 10days, working 4 or 5 hours each day (working longer in the cramped conditions was too much for me).

 

Lessons Learned:

• I wish that I had thrown away more junk - there were some long floor boards, so you needed space beyond the area being insulated.
• Our attic has reasonable lighting in the centre (two strip lights), but still not good enough. In hindsight installing lighting throughout, before I started would have made it easier (& easy with some LED lamps).
• I was worried that loft legs did not look robust enough. I needn't have worried the floor boards structure, with loft legs underneath is rigid and feels robust.

Cross-section view at attic hatch with one loft leg visible - the overall structure feels rigid and robust

 

• There are quite a few useful 'how to' guides on line.
• Using non-itchy insulation was a good move (the limited amount of original fibre glass insulation was bad enough)
• Not doing this at the height of summer was a good move
• We have a relatively large attic hatch with a built in ladder - if you do not already have this, then worth installing ahead of insulating, particularly if you use the attic for storage.
• I needn't have worried about a global shortage of insulating materials - the suppliers website promised 3 days and the insulation arrived in 3 days.

Insulation arrived within 3-days. Despite rapidly rising energy prices, there seemed to be no shortage on insulating material

 

Impact:

• Combined with other changes (small reduction in room target temperatures (1degC in some rooms) and reduced boiler flow temperature from 70degC to 65degC) this looks to be saving ~£300/year (see upcoming blog post with September '23 data) It is difficult to be certain which of these is the biggest impact; my expectation is that the majority of this is the loft insulation:
• We have since restored some of the temperature settings and it has not made that much difference to costs)
• My understanding is that the flow temperature has to be lower than 65degC to make a significant improvement in boiler efficiency (more on that in a future blog post on weather compensation)
• Increased comfort: The house felt warmer (eg in the morning when the heating had been off all night) & also warmed up quicker.
• I think that we can run with heating off completely for longer over the summer/autumn.

 

My summary:

While it was more effort than I had envisaged, definitely worth doing and a good return on investment at perhaps 4 or 5 years.

 

Smart Heating Controls - My Experience with Honeywell Evohome - Part 1

Introduction

During lockdown in 2020 it seemed like a good idea to get better control of our heating. My focus was better comfort, but saving energy would also be good. We had Evohome installed in September 2020.

 

So, with the perspective of 3.5 years after installation (Jan 2024), how has the system performed?

 

Note: when I wrote this review it grew and grew...

...I have therefore split it into two: in this post I have attempted a less technical overview and in an upcoming Part 2 I will focus on technical points.

 

What Did Evohome Replace and What Were the Problems

We had a simple dial thermostat in the hall; a 7-day programmable timer in the kitchen with traditional (1-5) Thermostatic Radiator Valves (TRVs) on each radiator:

• The 7-day programmer was a bit of an effort to set up. It was set to go on in the morning and evening during the week and all day at weekends. We hardly ever adjusted this over many years, other than on initial set up.
• We controlled temperature day to day by:
• Adjusting room thermostats (often to maximum or minimum)
• Adjusting the hall thermostat (often by quite big increments to get the 'click' of the contacts to 'kick' the boiler on or off)
• 'Advance' on the timer, eg in the evening, if we were staying up past the time when the timer went off.
• The bathroom was set to be always on (ie if there was hot water flowing to the radiators then the bathroom radiator was on) - it was explained to us by the installer that this was necessary as a pressure release if all the TRVs are off and the boiler is on.

All of this resulted in quite wide swings in temperature, a few household arguments and a few times waking up with a hangover, dehydrated and a really hot house because the heating had been on all night with radiators at maximum, after a late night drinking!

 

Selection & Installation

At the time I read various positive reviews of the Evohome system and it looked to be the only system to give individual radiator control.

 

The Evohome website gave me a local installer who quoted me based on photos of the existing TRVs, so that he could confirm there were no issues in the retrofit:

• 11 rooms/radiators to be fitted with a smart TRV
• 1 x hot water tank thermostat
• The price, with installation, was ~£1800. This included for an Automatic Bypass Valve (ABV) to allow all radiators (including the bathroom) to have Evohome TRVs (see part 2 for more details).

 

Installation was mostly straight forward and took one day; however there were a few gremlins. See part 2 for more details, but these would have been fixed in a couple of weeks / 2 visits by the installer, except that we had a pre-existing wiring fault, that credit to the installer, he tracked down and fixed (at additional cost).

 

By the end of October installation was complete, the system was now working well but our confidence in the Evohome system was low  (especially for my wife who just wanted a working system!) We had seen repeated gremlins and, even excluding the wiring fault, I had to resolve several issues during the first couple of months. Limited online support materials meant that this was somewhat trial and error (ie there may have been very few issues, but perhaps I initially caused more as I learnt how to trouble shoot).

 

Lessons learned:

• Ask the installer how many systems they have installed and if your installation has anything that they have not tackled before or that they see as a problem.
• Get a fixed price and defined scope of work (eg what happens if there are problems). Agree upfront the hourly rate for fixing problems that are outside of this scope. I had done this & so the agreement on extra costs (ie wiring fault) was transparent and there was no argument.
• If there are tricky issues then you need an installer who will stick with it and not give up. I got that in this case, but I am not sure how to judge this other than a sense of if you trust the installer. I think that to my benefit this was a smallish local company and I always got Mike to come and look at problems. I can imagine that  with some (larger) companies you might end up being passed around from person to person.
• I strongly recommend that anyone having Evohome installed takes an interest in the technology and any issues - I ended up learning more about central heating and Evohome than I really wanted to, but this ended up being useful longer term (see below and  part 2). It also gives a lot of materials for a very long blog post!
• Plan on an early summer install. Why? You will have plenty of time to learn the system and resolve issues before you really need Evohome to be 100% functional in winter. In addition, your installer/heating engineer will have better availability and may have lower hourly rates. My September install got into reliable operation just in time for the onset of winter proper (end of Oct), but I had to pay winter rates for some of the additional work.
• After the initial gremlins the system settled down and our confidence grew.
• Evohome has been working pretty smoothly for over 3 years now. Part of this is because when we do get issues (every few months) I have learnt enough to resolve them myself. This is much like other home technology that we have (eg phone, laptop, printer, etc) other than there is less material on YouTube to help.

 

Evohome Software

The software is pretty easy to use:

• Programming a new schedule is reasonably simple. It is much easier than our old 7 day controller.
• There is space for 1 extra schedule.
• The radiator temperature control is intuitive; it overrides the scheduled target temperature and then at the next scheduled temperature change the radiator controller returns to the scheduled target temperature.
• The handset and phone apps have different interfaces. Neither is better or worse just different.

Hand controller scheduling interface	Hand controller temperature override interface
iPhone scheduling interface	iPhone temperature override interface

• There are controls for the entire system (eg for when you go away), but these are limited:
• App 'Eco' mode on: with scheduled switch off time resolution of 1hour - reduces room temp by 3 degrees (but seems to have a bottom limit of about 16degC)
• App Heating On / off: switch on time has one day resolution & this does not turn off the hot water.
• Hot water has to be switched off/on separately from the heating
• The handheld display is different, but not any better.

 

The Evohome software is easy to use and fine for day to day operation - if you are considering buying Evohome do not get put off by the details and recommendations for Honeywell in part 2.

 

Living with Evohome - How we use it:

• We are getting used to switching the heating off when out:
• If we are out of the house for a few hours we tend to use Eco mode as you can set the on time by the hour
• For longer than one day we switch the heating off and try to remember to switch it back on from the phone app several hours before we are home to allow for warm up time. We also have to remember to switch the hot water off/on.
• We have the schedule set to turn off several times in the evening/night, eg 10pm, 11pm and midnight. This allows for those late nights:
• At 10pm the heating goes off (target 5degC)
• If we are staying up we can turn up specific radiators (usually at the radiator)
• These go off again at 11pm...etc.
• This prevents the heating being left on all night, in every room and waking up dehydrated (as well as hung over) as with our pre-Evohome heating control system.
• We have the schedule set to nudge up the temperature in some rooms in the evening; not sure if this is the same for everyone, but 19degC/20degC seems fine in the daytime but cold in the evening.
• We keep lounge cool and use a nice and cosy gas fire. The gas fire is not the most efficient, but has a really nice log effect. My suspicion is that this saves energy (cool lounge for much of the day and in late spring/summer/early autumn we often just use the gas fire and extend the time when the central heating is off completely).
• Battery costs:
• Each TRV (& the hot water thermostat) take 2 x AA batteries
• Very roughly each battery pair lasts 18months
• On our system this is about 24 batteries every 18months or 16 per year
• Amazon price £8-99 for 40 pack of batteries, or around £3.60 per year.
• Central heating service - no change, we still use the same bloke to service the boiler (ie not the Evohome installer) and I do the Evohome (battery replacement + occasional trouble shooting)
• The radiator controller does make a whirring noise when it adjusts the valve. For me this has become a re-assuring 'all is OK' sound. In most rooms the sound level is similar to the boiler firing up (ie not very much). However, it is another reason for not having 'optimum start' configured - at 6am every morning the radiator TRV in our bedroom makes its small whirring sound and the boiler fires up a few seconds later. Often I sleep right through this, but sometimes I am stirring early and I know what time it is; I am not sure that I want this noise varying between, say, 5am and 7am depending on how cold the morning is (but I may still try it).

 

My view of Evohome after 3 Years

• Comfort:
• Consistent and controlled: improved comfort through the day
• Heating not left on all night; waking up dehydrated and hot never happens now.
• To start with my wife hated the faff of learning a new system and teething issues with Evohome (over the 1st couple of months), but after 3 years she now prefers Evohome to our older controller.
• Ease of Use:
• Straight forward. Most day to day operations are:
• Adjust a room thermostat (easy on the app if we are out, but even easier to just change it at the TRV)
  

Adjustment of room temperature using the TRV knob is easy and the temperature automatically returns to schedule at the next scheduled time point.

 

• Turn heating off when we go out and back on before we come home (or using Eco mode to turn it down and then back up)

• Reliability:
• No hardware failures in 3+ years
• After initial 2 months/teething problems, perhaps one fault very 3 or 4 months (mostly resetting a TRV, and one receiver reset) + battery replacement.
• Batteries last 18 months, but each TRV and the hot water thermostat has them, so with 12 sets of batteries I end up changing one set every month or two. The TRV error message for batteries going is clear; it comes up on the handset and gives good early warning. The hot water thermostat battery warning was obscure ("comms fault") and I only discovered that changing the batteries fixed it by trial and error.
• Note battery life on the hand held display is poor. You can take the handset out of its nest for a few minutes (ie the opposite of a mobile phone that needs occasional charging, but spends most time away from the charger).

 

Financial Payback:

Evohome probably saves us some money each year, but the data on money saving, in our house, is mixed up with lifestyle changes (See earlier blog post, eg working at home in the pandemic) and also mixed up with other energy saving measures (eg loft insulation - see future blog post). So the impact of Evohome is hard to measure on its own. I read of 10% savings quoted by others and I can believe that this is true. That would be ~£200/year for us at current energy prices, so a payback of a little under 10 years plus a more comfortable house. I also think that Evohome gives you more control on saving money Vs comfort, ie you have the control to fine tune the savings to be more than the quoted 10%, if you are OK with lower temperatures (in particular rooms/times).

 

Final Thoughts:

• Evohome works well and, for us, is working as promised. My sense is that a complete technophobe might struggle, not in day to day operation, but with the faults that do occur every few months. Reading recent reviews (eg https://www.techradar.com/reviews/honeywell-evohome) it sounds like Evohome is still one of the leading systems and also one of the most user-friendly. If that is the case (& if my system is typical) then my view would be that smart radiator controls are not ready for the mainstream quite yet:
• Better support materials required (3rd party and supplier)
• Better guided fault diagnosis and resolution within the system (eg my 5 year old, low cost, HP printer is great for this)
• Build in more fault tolerance (see part 2 for more on this)
• The length of this article tells you that, from knowing very little about central heating, installing Evohome has taught me more than I ever wanted to know.
• If you are moderately technology savvy (eg comfortable trouble shooting home wifi, printers, laptops, etc) and interested to learn, then you should be fine (I have an Engineering background, but I am sure that this is not necessary). However, if your first response to any technology error is to call someone else then you should anticipate a cold radiator or two, once or twice each winter while you wait for help to arrive! When help does arrive, if this person is technology savvy, but new to Evohome, then the lack of online support materials will be a hindrance.
• Evohome has given us a more comfortable home; we get a more controllable & consistent temperature. My wife was dubious early on, but now likes Evohome purely from a comfort/control viewpoint.