Existing central heating control systems

A little while ago I wrote some notes describing my "ideal" central heating control system, which I was planning to build myself.  Time is short so it looks like this system won't be built for a while so I need something which I can buy off-the-shelf which will satisfy as many of my requirements as possible and also leave the door open to DIY tinkering in the future.  This blog post is a collection of notes about off-the-shelf central heating control systems.


  1. Programmable room thermostat in each room (which senses the temperature in the room, compares that to a temperature schedule for that room and turns on the TRV valves on the room's radiator if necessary).  This could be integrated into the TRV. 
  2. All communication should be wireless. (I have run a few cables around the house but not for every room).
  3. Room thermostats must be able to signal to the boiler to request more heat.  Having a single boiler schedule and thermostat to control the boiler is so utterly dumb it's frightening.
  4. The system needs to be able to work with our underfloor heating
  5. It would be awesome if the system could be controlled from a laptop / iPad / Android phone / iPhone, both within the house and outside the house

Current Plan

I need to explore the ELV MAX! system.  Very good prices.  Has radiator TRVs, room thermostats and a LAN gateway.  Hekkers has done lots of work with with ELV MAX! system (including talking to them)

Look into the AlertMe smart heating kit available though British Gas.

I should also check for new products on http://www.automatedhome.co.uk/category/hvac

...and figure out what this very affordable wireless Conrad TRV does.

...and look into http://www.salus-tech.com (they do programmable TRVs and a bunch of other stuff) (thanks Derek for the link!)

... and look into Owl's heating controls!...

The LightwaveRF system looks like a good bet.  There are some questions I need to answer before going for it though (see below).  LightwaveRF do have some TRV valves on the market today but these are one-directional (and hence can't call for heat from the boiler).  "Complete zonal bi-directional heating control system (early spring 2012)". The last forum post on the topic suggests that LightwaveRF's heating kit might be available Q3/Q4 2012.  The LightwaveRF Android software gets rather bad reviews.

If LightwaveRF doesn't work out then the idea I'm thinking of is something like this: use Conrad Wireless TRVs, Room Thermostats and Boiler Control for basic heating control (still need to figure out exactly how the FS20 system will control the UFH). Then use a Nanode+JeeLabsWireless to add an open-source "Internet gateway" to the FS20 system to allow for remote control and monitoring of the heating system. One of the nice properties of this system is that, when we move house (which may be in only a few year's time), I can remove the DIY components from the system (i.e. the Nanode) and the core FS20 system will continue to work.

I still need to look into the Homematic system.

And I also need to consider if I really want central programming.  The easiest solution would be just to add programmable TRV heads to each radiator (can be bought for £15-35 each) and forget about controlling the system from the network.  I could add a simple Nanode system to turn the boiler on/off from the web.



  • hackable / open API? (some discussion of protocol here and here)
  • how to control boiler?
  • how to control UFH? (the TRV replacement heads won't fit on my UFH manifold) guessing I'll have to use a switchable mains socket or something
  • I've heard the heating system can only do 3 zones, is this correct?

FS20 System

Controlling our living room UFH system

Current plan: will probably have to give up on the living room's UFH being connected to the boiler and/or the other controls.

Option 1

Buy the HomeMatic 4-zone Under Floor Heating system For 630 euros. This is way over my budget and I only have two UFH zones. So this option is far from optimal but it does demonstrate that it is possible to control UFH with FS20

Option 2

Buy the FLV wireless thermostat plus wireless mains switch for 55.95 euros. Use the mains switch in series with a wired floor probe thermostat to control a wired actuator (i.e. heat will only be sent to the floor IF the FS20 thermostat calls for heat AND IF the floor temperature is below 28 degrees C). Big question: will this system work with the FHT8W Boiler Control? (I'd guess it does) (update 21/9/10 - no, the STR thermostat wont work with either the FHT 8W or the FHZ1xxx PC controllers)

Option 3

Buy a Conrad FHT 80B Room Thermostat, a FS20 AS1 switch and the FHT8W Boiler Control and hope that the 80B can be configured to talk to the AS1 switch. This wont work if the 80B cannot communicate with the AS1 switch. (update 21/9/10 - the 80B cannot work with the AS1 switch)

Option 4

Buy an FS20 room thermostat plus wireless actuator plus window sensor. Hack the window sensor so that it is connected to a wired floor temperature probe. This will almost certainly work. The components could be bought from Conrad-UK or from HouseTechSolutions. (update 21/9/10 - won't work: the FS20 wireless actuators are too bulky to fit onto UFH manifolds!)

Honeywell Total Connect

  • http://www.mytotalconnect.com/comfort/yourhome.php
  • No details at all.  Cost?  Tech specs?  Detailed feature list?!  Nope; just patronising stock photos of "happy families".
  • Prestige 2.0 thermostat costs £279 each!  Rediculous!  But, wait - it comes with a "high definition" display; oh joy</snark>.  Seriously guys; stop taking the piss.

Bridging the FS20 wireless network to a TCP/IP network or a computer

The FHZ1300 Radio Home Centre PC bridges from the FS20 wireless network to a PC via USB.  Apparently the software supplied with the FHZ1300 is all in German). PC can then either run the Homeputer Web Server for £44 or the GPL'd Fhem software. There is a FHEM iPhone app in development too (or was it just a proof of concept?). The software is well maintained and the web stuff is optimised for Android browser. There are more software apps listed here: http://fhz4linux.info/tiki-index.php

Simple programmable TRV heads

If you simply want programmable thermostats & actuators built into a TRV head then such things can be bought for as little as £15.  But none seem to be network-connected.  (e.g. search the Conrad website for Honeywell HR20). Honeywell make an HR80UK (£80) which wirelessly connects to either the CM Zone or Evotouch Control Panel.

Wired actuators

Thermal actuator TS 230 V

Thermal actuator TS+


Multi-Fit Thermal Actuator 24v (Low Voltage)

Multi-Fit Thermal Actuator 230v

Programmable room thermostats


Networked programmable room thermostats


  • Do a wide range of room thermostats including wired, wireless and WiFi. Expensive though.  WiFi thermostats start at £149 each.
  • Their "Internet Remote Control" costs £383!

John Guest

  • The John Guest Programmable Room Thermostats can definitely be controlled from the web although it's not clear if this control has to be done via several hundred quid's worth of boxes or if the thermostats have an Ethernet port. I've emailed to ask

1-wire interface to Lux thermostats


Hacking the Honeywell HR20





"KNX is a standardised (EN 50090, ISO/IEC 14543), OSI-based network communications protocol for intelligent buildings. KNX is the successor to, and convergence of, three previous standards: the European Home Systems Protocol (EHS), BatiBUS, and the European Installation Bus (EIB or Instabus). The KNX standard is administered by the Konnex Association."



A Google Shopping search for "KNX room thermostat" suggests they start at £125.

There's a KNX touch panel with integrated web server for access from the web / iPhone http://www.iddero.com/en/products.php

And there's a KNX Siemens IP viewer gateway thingy for about £500 http://www.knxstore.com/knxstore/product/8/siemens-knx-ip-viewer-n-151/lang/en

There's a KNX valve actuator for £50 http://www.knxstore.com/knxstore/product/48/siemens-knx-230v-ac-valve-drive-electro-therm-ap-560r



An interesting forum topic on OpenTherm boilers and room stats: http://www.diynot.com/forums/viewtopic.php?t=222182&postdays=0&postorder=asc&start=0

Tech notes

  • The connector for TRVs is "swivel nut (M 30x1.5)"

Quick rant

Having been through the pain of searching for decent home heating systems, I can't help thinking that this market is long overdue a fundamental shake up.  Most "modern" products are obscenely over priced, come with a miserable feature set and are pro-install only.  If someone can come up with a decent-priced, DIY-installed, wireless heating control system, with a TCP/IP bridge and an open API (to allow 3rd party developers to build iOS / Android apps) then I'll be first in the queue.  The market for thermostats seems to be stuck in the mid-1990s.  Honeywell, for example, lists "high-definition full-color display" as the most important feature of its top-spec thermostats, FFS; yet a 2.5" colour TFT touch screen is only £10 from Farnell.

update 13/3/2012: Ars Technica has an article entitled "The five technologies that will transform homes of the future."  Guess what number 2 is?  Smart heating and power systems!  (they don't mention disaggregation though)

update 7/12/2015http://www.wifithing.com - "internet of things made simple" have some home heating controls.


Very informative and sensible blog. Thank you.

I agree 100% with your summary rant.

Hi Jack

Just read your posting on heating control systems with great interest. I've
been on a bit of a journey with this myself, and although my system is
currently rather more straightforward than yours (ie no underfloor heating)
I've just installed a basic FHT system and it's working quite well.

I've currently got two of the room thermostats, each driving two valve
actuators each (so basically two zones, upstairs and downstairs) with the FHT
8W boiler control unit. It's taken a bit of getting used to but it's doing a
good job of controlling the heating and it's great for (eg) not heating the
bedrooms in the evening etc.

I've just had the CUL USB device delivered, and althought this was expensive
(about £60 delivered) it runs with FHEM and gives fine control of the
devices as well as some quite nice logging for each room. This also gives the
internet control you were after.

The CUL device also works with a whole range of other wireless sensor
protocols (such as temperature sensors for weather stations etc). It strikes
me that one solution to your UFH problem would be to hack the floor
temperature sensor into a form which FHEM could understand (or else buy an
FS20 temp sensor of which there is a vast range at ELV / Conrad). Then you
could use FHEM to interpret the temperature readings and trigger the boiler
(you'd have to use a separate AS1 switch).

If you were happy using FHEM to control the whole system you wouldn't need an
FHT 8W at all, you could just use FHEM to read from the room thermostats and
write your own logic to trigger the boiler.

Anyway would be happy to discuss further, not many people seem to be using
this kit in the UK.


hi James,

Thanks loads for getting in touch - it's great to hear your experiences of the FHT system.

I'm planning to not install any "smart" control kit for our heating system this winter. Instead I'm going to wait until next winter, in the hopes that the LightwaveRF kit will be relatively bug-free by then.

Good luck with your tinkering,

Hi Jack

Thanks for this.

You might be interested in the attached screenshots from FHEM as well.

Why have you settled on LightwaveRF? I'd not heard of it before, but on a brief look it looks rather less mature and supported than some of the other options. Hope it works out well for you - I'd planned to do this last year but stopped because the summer caught up with me... and then my old thermostat finally packed up which got me into it! I'd be really interested to hear how you get on, especially as I may go for UFH in the future.


Hi James,

Thanks loads for the screen shots; very interesting.

I haven't decided for sure that I'll use LightwaveRF rather than FS20.  I agree that the LightwaveRF software appears to be rather immature at the moment.  One big problem with the FS20 kit is that there seems to be no way to integrate my UFH with the rest of the heating system.  And I like the fact that LightwaveRF are planning to produce a documented API.

very interesting, thank you

It's an exhausting list, thanks for the post! Where do you think I should start if I want to optimize my house for heating?

found this as I am trying to do the same thing, with the kit I already have,
what I have:
Lightwaverf wifi link
Pegler ITemp Terrier radiator valves (* 6)
LigthwaveRF Inline Relay
Various Temper usb devices.

I have got to the point where I can individually control the valves using the API I wrote for the wifilink - the valves appear to be compatible with the lightwave ones - so think the window is open when I send the radiator off command, and closed when I send on (so kinda works)

Idea is to put the relay on the boiler control - then timing and boiler control can be done by that relay (for the heating) then to somehow get temperatures from each room, and store things like time that x temperature is required, and the last rate of change of temperature whilst the radiator was on - so that the heating will come on earlier if it is colder - also get it to factor in the outside temperature by querying weather online for my location - and factor that into the amount of heat supplied.

IF anyone wants to help me - get in touch...

very cool - thanks loads for the info. I haven't done any work on my home's heating control over summer but now that the weather is starting to get cold and miserable I might well start tinkering again; quite probably with LightwaveRF kit. Thanks,

Hi Jack,

I read your various posts with interest as I am in the process of developing a similar whole-house control system, and my list of ideal requirements is almost identical to yours. Like you, I have been underwhelmed by the products available at reasonable cost, especially when the requirement is for anything beyond an electronic version of a standard TRV.

My intention for the rads is to integrate an off-the-shelf low cost TRV head with my own wireless sensor/bridge platform. I have been looking at the on-air protocol for the Conrad FHT8V using Gnuradio, and I have just completed a similar analysis of the Terrier i-Temp which I am aiming to write up later today. The FHT is the front-runner at the moment as the Peggler valves are not very hacker-friendly - glob-topped chips and what appears to be a code hopping protocol (although I noticed someone above saying they have had success communicating with them).

For room occupancy the house alarm is providing live PIR data via a custom interface. Currently, this is just being logged to determine its worth in determining room occupancy probability, but early indications suggest it is quite usable.



FYI: I'm trying to start an 'OpenTRV' (open source hardware and software) design which aims to address many of the features that you and I think desirable. We may be able to get something done in time to catch the tail end of this winter:




Damon, the OpenTRV project sounds superb and exactly the sort of project I was really hoping that someone would start! As you say in your blog, intelligent control of room-by-room heating could significantly improve energy efficiency without reducing comfort (possibly even increasing comfort!)

Some quick thoughts:

  • The OpenTRV project is something I'd love to get involved with. Unfortunately I don't have a huge amount of free time at the moment so I probably won't be able to do much hands-on development work. However, I'd be very eager to offer any help I can. I recently reverse-engineered the Current Cost protocol (with help from others) and built a DIY Current Cost receiver using a Nanode with a 433MHz RFM12b so embedded coding is quite fresh in my mind at the moment (although I'm by no means an expert!).
  • On the topic of hardware: JeeNodes / Nanode RFs appear to be a great platform, with lots and lots of community support. The JeeLabs room node provides a solution for room-by-room temperature logging. Building a wireless TRV compatible with the JeeNodes system might be a great aim. Making use of the JeeLib library would not only save time, but would also mean that lots of existing JeeLibs users would very quickly be able to contribute to OpenTRV.
  • My hunch would be that Zigbee is overkill and that a solution based on an RFM12b (with ACKs and checksums) would work perfectly for most houses. Zigbee would probably only be required if you wanted to be able to target very large buildings (like schools or offices).
  • In terms of system design: one disadvantage of making each TRV responsible for storing its own schedule is that then you need to add a real-time clock to the TRV, which adds expense and complexity (not much but it all adds up). I wonder if it might be simpler to do something like this:
    • The TRVs:
    • each TRV only stores its current target temperature.
    • The TRV would periodically (one a minute?) ask the base unit if it needs to modify its target temp.
    • If the actual temp drops below the target temp then it opens the valve and polls the base unit to ask for heat from the boiler (and the base unit must acknowledge).
    • The TRV might have a manual-override on it where the user can alter the current target temp.
    • The TRV could have a very simple display (just displaying the target temp, the actual temp and whether the valve is open or closed) - the display doesn't need to represent a schedule.
    • The TRV could have a "slave" mode where it only opens and closes its valve in response to commands from the base unit (instead of on the basis of its local temperature measurement). This would allow us to use external temperature sensors in each room (e.g. a JeeLabs room node).
    • The base unit:
    • It would be the base unit's responsibility to store the schedule and to tell each TRV to modify its target temperature at specific time points. This makes it relatively simple to modify the schedule over the network (because the schedule is stored at one place).
  • Here at Imperial College, MSc students do 3-month individual projects over summer. They will be choosing their projects over the next couple of weeks. I'd be very eager to propose a student project on OpenTRV. (i.e. we'd have at least one MSc student working on the project for 3-months. They'd be computer science students so they'd probably be mostly interested in the embedded software / UI rather than the hardware design. And I'd have to check with my PhD supervisor)
  • If you're near London then it'd be great to meet to discuss in more detail
  • LightwaveRF are about to release their new heating control system. People have had success in communicating directly with the LightwaveRF WiFi link device. So if the LightwaveRF TRVs are cost-effective then perhaps it'd make sense to just write the software for communicating with the LightwaveRF hardware?


Wow, what a great comprehensive response, thanks!

I am in London: email me (link at the bottom of each page on my site) and we can sort out a beer/coffee etc.

Would be lovely to get a student on the case for the next round of this.

I have spoken to LightwaveRF, etc, but some of the goal of this is to have at least one solution (but not the ONLY one) that we don't have to reverse engineer or rely on the whims of manufacturers changing things.

As to how much smartness should be in the TRVs: definitely a matter for debate, agreed. Let's discuss more. But for the moment the model in my head is a relatively dumb unit at the boiler possible which just responds to call for heat from any TRV, with the TRVs being autonomous like (say) the i-temp i30, to minimise the amount of chatter required, etc. But again, that shouldn't be the only solution possible, it just fits with something I could deploy immediately to test before winter expires!



Hi Jack,

Thanks for the solid summary of the players in this area. Your requirements list is very close to mine & I share your 'Rant' thoughts - it really shouldn't be this hard to do!

I've already deployed wireless temperature/movement/light level sensor units to my rooms. These report back to my HA system. http://www.dbzoo.com/livebox/hah_hahnode/airwick

Radiators are fitted with i-Temp i30 TRVs. I've had confirmation from Steve Aitken that the LightwaveRF WiFi link can address individual valves & cause them to 'setback'/'open'. Ideally, I'd like to do my own hardware for this - the LightwaveRF box is rather pricey and I already have my scriptable internet gateway platform http://www.homeautomationhub.com - but the RF protocol is hard to hack.

Boiler control is also in place by emulating the RF signal (433MHz) from the Drayton Digistat +2RF thermostat. The 'call for heat' signal must be repeated every few minutes or the boiler will shutdown. However, SWMBO is not keen on the idea of ditching the actual Digistat until she has a simple way to get manual control of the alternative solution.

Lots of integration work to be done to pull all this off.


p.s. Noticed that Salus http://www.salus-tech.com now offer an internet gateway/mobile app for their nice programmable TRVs.

Hi Derek,

Thanks loads for the comment. Those links are very interesting. I wasn't aware of Salus Tech until your comment: their kit looks very interesting!

Best of luck with your project, Thanks, Jack

Derek, I've just done a little more reading of your links. You've worked on some really interesting stuff! I've been following the HAH project for a little while now: it's a great project!

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