Intelligent Heating Control – First Steps

As promised I’m now turning my attention to a different project. For a long time I have wanted to handle control of my heating system much more intelligently than just relying on a single thermostat. My house is a fairly large Victorian terrace spread over three floors, and the rooms are large with high ceilings. At the moment the thermostat is in the hall, and this is supposed to take account of the heat in all the rooms of the whole house. It seems a very blunt instrument and I’m sure I’m wasting a lot of heat.

This sort of thing is topical and there have been products such as the much-vaunted Nest thermostat. However, I’m really unimpressed with this – because no matter how fancy it is it only samples heat from one place. If you live in a small flat then that’s fine – but it doesn’t help my situation.

As well as having more sampling points, you should also have more control over how the heat is distributed. Nest etc only control whether the boiler / heat source is on or off – not where the heat is going. My house uses standard gas-fired heating with radiators and thermostatic radiator valves (TRVs) but I’ve never been very satisfied with these. Also of course they don’t provide any control of the boiler.

It seems I’m not alone in this – there are a small number of products out there which address this issue, and the most recent and most consumer friendly is the Honeywell EvoHome system.

honeywell_evohome_connected_thermostat_pack_atp921r3100_hr924uk_radiator_controllers

This does look very interesting but I’m not pursuing it for various reasons (mostly because I don’t want to have to start again with a new system). There does seem to be a lot of discussion about it in the AutomatedHome forum

The basic idea is that you have one or more replacement TRVs which are motorised and have a temperature sensor. The valves report back their temperature to a central control point, which is then able to control the boiler to switch on as the need to heat each radiator arises. This feedback is the big plus over a normal TRV (which really only regulate maximum heat) as it allows them to regulate minimum heat too. When heat is called for, only the radiators which need it will be on and so the heat is much more efficiently transferred to where it is needed.

I’ve been looking at these systems for quite a few years now. When I first started about 5 years ago, the only thing out there was the FHT range. This is based on the FS20 protocol, which seems to be very well-established in Europe and particularly Germany. There is an enormous range of FS20 kit available, far more than any equivalent system used in the UK. However, it seems little known about here. The FHT system involved a separate valve motor (FHT 8V) and room thermostat. The motor adjusted the valve depending on the temperature, and a separate boiler interlock (FHT 8W) which listened to the settings of the valve motors, and when they reached a certain level it triggered the boiler. The FHT 8W is a remarkably overengineered piece of kit – I bought one at great expense (about £80) but I don’t think many other people in the UK did.

fht8w_heatrelay_1

I had this system (two or three thermostats and the boiler switch) in my old house which was much smaller, and it did seem to work quite well. I discussed this quite a bit at the time on various forums and blogs (see discussion with Jack Kelly who goes into the whole subject in some detail). However, when I moved house the FHT kit remained very expensive and I rather lost interest in the whole idea as other more pressing work took over.

The other thing which I did get from my first attempt was computer control of the system. I was not satisfied with just the kit, I wanted to monitor and control it much more closely. Once again, I found that the Germans were very far ahead of us. Through reading various forums (thank goodness for Google Translate) I learned about FHEM. This is very mature and well established home automation control system. I’ve been following home automation for years (and I have a developing Z-Wave system for lights etc which I’ll talk about some other time) and am aware of various software systems.

However FHEM stands out for a number of reasons – it is unashamedly geeky and flexible (hence it suits me well), it is extremely well supported (if you speak German) and has support for the widest number of different systems that I’ve ever seen. To get it to talk to the FS20 system I needed a CUL1101 device. At the time I got mine the only place you could get them was from busware which is another German company. It was rather expensive (about 50 Euros although they are more now) but gave me what I needed to interface FHT with FHEM and read out the data to plot some graphs. However I never got much beyond this and I was aware I hadn’t really made the most of it.

This is pretty much where I got up to before I picked it up again recently – which I’ll cover in the next post.

 

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