Automating Heating - Intro

Paul Goulbourn

I can’t justify the extra expense of adding significant additional battery capacity to my solar installation with its current pricing. However, it’s interesting to note that having crunched the numbers, vehicle-to-home would have virtually eliminated all our grid consumption through the summer. It would only have been days when we needed to perform longer trips in the car on repeated days that would have caused us to import any energy at all.

However, over the last few weeks winter has finally begun to bite in the UK. Our solar panels are east-facing, and the sun is starting to rise further and further south, so solar generation is dropping off. (We are consuming all produced, but have a lot less to play with).

Our focus, therefore, turned to the other main energy cost to the household - gas. Our central heating is a gas-powered boiler to radiators throughout the house.

We have a basic Hive system installed, i.e. a single thermostat in the hallway that controls the boiler. This works on a simple schedule with periods of the day alongside requested temperatures. The individual radiators have simple valves on them - set 0-6 to control the temperature in any room. However, if a room feels cold turning a radiator up won’t provide any heat unless the thermostat in the hallway is below the household level. So to get the heat you then need to “boost” the main heating, forcing the boiler on and warm water to flow.

This feels inefficient, heat the whole house because one room feels cool. Of course, you could run around to all the other radiators turning them down, but the reality is that nobody is doing that.

Enter Hive TRVs. These are battery-powered thermostatic radiator valves. They are part of the Hive product suite and can talk directly to the boiler. Each valve has its schedule and temperature targets. If the temperature in that room drops below the required level it can “call for heat” and turn the boiler on.

We looked at these valves when we moved into the house in 2019, but then the reviews were horrific. The main issues seemed to be around connectivity. After a few firmware releases things seemed to be better so we decided to invest during the black Friday sale.

The good :

  • The installation is simple, and the app works well to add them.
  • The TRVs are set by temperature eg. 19C rather than a scale of 1-6.
  • They look nice, aesthetics count when they are going into every room.
  • They work well, once they settled in we all noticed we hadn’t needed to mess around with radiators.

The bad :

  • Every radiator needs a schedule created for the week. You can’t copy schedules between radiators. I’ve installed 18 of these things, with 18 schedules.
  • The Hive app doesn’t have any concept of a room. So if you have 2 radiators in a room, they have two different schedules.
  • The thermometers are part of the valve, so they are subject to fluctuations from the radiator itself.
  • Multiple radiators and valves in the same room don’t act together, one can call for heat whilst the other says it’s over temperatures.
  • They are fairly expensive £30+ each in the sale.

Before we bought any I made sure that they worked in Home Assistant. They integrate well, the aim is to create routines that will override the default schedules. So like in the previous post on electricity usage determine if people are in a room and turn the heating down as appropriate.