St Andrew's Church

Smart Central Heating Controls

Contributed by Mike Kerslake

I'd seen brands like Hive and Google Nest advertise their products for managing your home heating more efficiently and last year decided to install a system at home to - hopefully - reduce our household carbon footprint as well as our heating bills. After a debacle with Google's Nest system (neither I nor my plumber could get it to work) we installed Hive which is the system promoted by British Gas. There are all kinds of home automation things the system can do, but my intention was simply to try to save energy by only heating rooms at times they were likely to be in use. So we installed the basic heating system controller plus smart radiator valves in selected rooms. Some of our radiators didn't have the right connections to allow the smart valves to be fitted easily so it's not as complete as I would like. But our basic strategy is this:

 

Bedrooms: Only heated in the morning and late evening

Dining room: only heated from late afternoon until mid-evening

Living room: Only heated from mid to late evening

 

The rest of the house follows the basic daily heating schedule like a conventional system. We've tried to get further savings by manually turning off the radiator in the kitchen, on the basis that the kitchen gets warm anyway when cooking. But of course this means the kitchen is a bit chilly when we're not actually cooking. And we have a bedroom that's currently not used so we've simply manually turned off the radiator there.

 

The big question of course is, how much are we saving?

 

I'm always a bit sceptical about headline claims for energy savings for systems like this because there are so many factors involved - not least the weather - and, in our case, the fact our son started at university last autumn reducing our household to three people a lot of the time now instead of four. But being something of a geek I have records of our gas consumption going back a long way, so I've been able to correlate our gas consumption against published weather records to compare our new "smart" system to energy consumption in previous winters. December 2022 was on average a cold month, comparable to January 2017 and February 2015. Our gas consumption with the Hive system was 27-36% lower than for those previous months, which is a very promising start! But I'd like to collect several months of cold weather data before drawing any definite conclusions. Having one fewer person living here is offset by me being at home most days last December (in contrast I was office working in 2015 and 2017) so I do think most of the savings will be attributable to our room-by-room control. But time will tell.

 

With parts of the house unheated at certain times we've had to change our behaviour a bit to stay cosy but the biggest challenge with zoned heating has been keeping doors closed between different zones. The worst culprit is the cat who roams around the house, leaving doors wide open with apparently no interest in my energy saving ideas! Restricting him to certain rooms is a possibility but a better solution - suggested by my daughter - would be to install cat flaps in one or two of the internal doors! This would allow him to roam freely always shutting the door behind him! Then we would just have the humans to blame...

 

With our "hybrid" system where the hall thermostat controls the boiler, some rooms have smart controls, others conventional thermostatic valves and others just manual valves, it's taken a little experimentation to make the boiler fire up when we want heat but not when we don't. For example, with the living room set to warm up later than the dining room, at first we found the boiler wouldn't run enough to warm up the living room because the rest of the house was already warm. We overcame this by adjusting the flow on the hall radiator, so the hall tends to warm up more slowly, and we added a step in the program to boost the hall temperature a little just at the time when the living room starts to warm up. This means the boiler will come to raise the hall temperature, providing heat to the living room as well. 

 

We had a plumber install the main controller which was a bit tricky because it emerged there were some wiring errors dating back to when the house was built that needed to be corrected. But the radiator valves are a straightforward DIY job, as long as the radiator has a compatible fitting. They are battery powered and need to be linked by Wi-Fi but don't need any wiring. The system is controlled via a phone app which is reasonably straightforward to use, and there are also some basic controls on the hall thermostat. The only reliability issue we've seen is that Hive's server went unavailable for about a day recently, making the phone app unusable. The heating system still worked, with some manual control possible, but system behaviour was a bit odd and, unfortunately, I have to say Hive's customer support was very poor. The radiator valves are meant to calibrate themselves to match each individual radiator but one of them seems to lose its calibration now and again. It continues to work, but will probably run its battery down a bit faster and may not control the temperature quite as accurately. But I've not noticed the difference - other than the calibration issue being shown on the app.

 

Where next? Well, I'd like to get the incompatible radiators updated with the right fittings to allow either smart or conventional thermostatic valves fitted. I have a box full of the conventional TRVs that we removed when fitting the smart valves, and in a frequently used room like the kitchen these would be a good solution at low cost. But I'll wait until after the winter to do this as it requires the central heating to be shut down.

 

Would I recommend it?

Yes, but with some reservations. Our strategy of zoning the heating to come on at different times wouldn't really have much value in a small studio apartment, and may not benefit all households depending on people's daily routines. (And their pet's!) But other features that we don't currently use - such as the ability to remotely control your heating from your phone - might be great for some people's lifestyles. Our home, with a mix of conventional and smart controls, is rather a compromise and if I were starting from scratch I'd want to update all the radiators in one go to be compatible with the smart valves. Finally, Hive is only one option with others on the market, so for a new installation I'd want to price up the supplier options and compare their features carefully.